December 2003

December, 2003 244 DOS Times - Vol.9, No.6

EDITORIAL

Dear friends, Though initially Lasik was recom- Though not practiced in our country
There have mended for all degrees of myopia it is till recently, there are few centers that
now clear that this procedure is not rec- have started adopting this new tech-
been extraordi- ommended in very high myopias (>- nique. R.P.Centre has initiated a project
nary develop- 10D). This is because of limitation in to study the role of Phakic IOL in our
ments in the night vision, loss of best spectacle cor- Indian setup with special emphasis on
field of refrac- rected usual acuity, visual aberrations its long-term safety.
tive surgery in and diminished quality of vision. The
the past few surgeon’s goal is not only to provide a It is a well-observed fact that refrac-
years. State of satisfactory postoperative visual acuity tive surgery is often patient driven and
the art technol- but also a good quality of vision. sometimes they push the ophthalmolo-
ogy is being de- gist to provide surgical relief from their
veloped and used for the treatment of We are entering a new age with the dependence on optical devices. There-
refractive errors. It all started with man’s introduction of phakic IOLs for correc- fore the ophthalmologists has a special
desire to get rid of his dependence on tion of high refractive errors where we responsibility towards the patients, to be
spectacles which drove ophthalmologist implant IOL leaving crystalline lens in- sure that the patient has a realistic ex-
in the early seventies to experiment with tact. Apart from providing excellent re- pectation about surgery and that they are
procedures that changed the corneal cur- fractive accuracy, it preserves corneal not solely guided by enthusiastic media
vature to achieve emetropia, the ultimate sphericity and allows rapid visual recov- claims. Patients must understand both
goal of any eye surgeon. Radial Kerato- ery. Compared with techniques that the advantages and disadvantages of the
tomy was considered a revolution of sort change corneal curvature like Lasik, surgery and accept that there may be
when it was first introduced. But as the phakic IOL styles & designs are capable complications from any surgical proce-
side affects began to show up newer tech- of providing the patient with best visual dure. These patients must be counseled
niques surfaced. First came PRK and acuity, better quality of vision and qual- and must be told of the risk involved
then Lasik. Emergence of excimer laser ity of image. Its main advantage over even though the percentage of success
and its dominance in refractive corneal corneal surgery is that it is reversible. may be high.
surgery is one of the most significant However there is some concern about its
advances in recent times. Harnessing the safety in the long run and also that it Thanks,
laser to safely perform corneal surgery demands more surgical skill than the Dr. Jeewan S. Titiyal
has been a major technical achievement. routine cataract surgery. Secretary

Programme for DOS Monthly Clinical Meeting for December 2003

Venue: Library, Venu Eye Institute & Research Centre, New Delhi 10 Mins.
Date & Time : 27th December, 2003 (Saturday) at 2.30 P.M. 10 Mins.

Case Presentation 20 Mins.
1. Combined Penetrating Keratoplasty and R.D. Surgery................... Dr. Reny
10 Mins.
using a Temporary Keratoprosthesis 10 Mins.
2. Macular Ischaemia following .............................................................. Dr. Arundhati 10 Mins.

Intravitreal injection of an aminoglycoside

Clinical Talk

l Dry Eye .................................................................................................... Dr. Ashu Agarwal
Mini Symposium: Low Vision

Chairman : Dr. S.C. Gupta,

Convenor : Dr. Anil Tara
1. Assessment of a Low Vision Patient .................................................. Dr. Sunita
2. Optical & Non-optical Low Vision Devices ...................................... Dr. Gaurav
3. Indications & Therapeutic Options .................................................... Dr. Ajay

Panel Discussions : 15 min.
Followed by Tea

December, 2003 245 DOS Times - Vol.9, No.6

LETTERS TO EDITOR

Letters to Editor

Low Vision in India In another population-based References
study in Andhra Pradesh, persons of
Dear Editor, all ages were examined4. In this 1. Murthy, GVS, Gupta, S, Tewari, HK,
Low Vision corresponds to visual study, Low Vision was defined as Jose, R, Bachani, D. Eds. National Sur-
permanent visual impairment that vey on Blindness & Visual Outcomes
acuity of less than 6/18, but equal to was not correctable with refractive after Cataract Surgery 2001-02. Report.
or better than 3/60 in the better eye error or surgical intervention. The National Programme for Control of
with best possible correction, accord- participants with best-corrected dis- Blindness, Directorate General of Health
ing to the International Classification tance visual acuity of <6/18 to per- Services, Ministry of Health and Fam-
of Diseases (10th edition). ception of light or central visual field ily Welfare, Government of India, New
<10 degrees because of an Delhi.
In the National Survey on Blind- untreatable cause in both eyes were
ness (2001-02) conducted under the considered as having Low Vision. 2. Murthy, GVS, Gupta, SK et al. Refrac-
National Programme Control of The prevalence of Low Vision was tive error study in children in an urban
Blindness, 63337 persons aged 50 estimated to be 1.05%. population in New Delhi. IOVS, March
years and above were examined in 2002, Vol. 43, No.3: 623-631.
15 states of the country1. The preva- The available data thus suggests
lence of Low Vision was estimated an estimated prevalence of Low Vi- 3. Dandona, R, Dandona, L et al. Refrac-
to be 10.3%. Extrapolating this figure sion of 1-1.5% in India, in the gen- tive error study in children in a rural
to the entire population, the preva- eral population, though there is wide population in India. IOVS, March 2002,
lence of Low Vision in the general geographic variation, and there is a Vol. 43, No.3: 615-622.
population approximates 1.3%. paucity of data on Low Vision in the
young adult population. This is ap- 4. Dandon, R, Dandona, L et al. Planning
In a population-based study in proximately 2.1/2-3 times the preva- Low Vision Services in India: a popula-
urban Delhi, children aged 5-15 years lence of blindness, when blindness is tion based perspective. Ophthalmology
were examined2. The prevalence of defined by the W.H.O. criteria. Ad- 2002 Oct; 109(10): 1871-8.
Low Vision was 0.22% in this age- equate attention needs to be paid for
group. In a similar study in rural provision of available and accessible Dr. Sanjeev K. Gupta,
Andhra Pradesh, the prevalence of Low Vision Services in our country. Dr. G.V.S. Murthy,
Low Vision was found to be 0.15% Dr. Praveen Vashist
in the age-group 7-15 years3.
Community Ophthalmology Deptt.
Dr. R.P. Centre for Ophthalmic Sciences,

AIIMS, New Delhi

Pre-Retinal Blood Aspiration-hydraulic Help – A New Surgical Technique

Dear Editor, ten dispersed and could be easily as- We do no recommended that hy-
After pars plana vitrectomy a thin pirated. This step is repeated in the draulic technique be used over the
area where pre-retinal blood could optic disc and fovea for fear of in-
layer of blood may often be present not be aspirated otherwise. We have ducting traumatic hydraulic dam-
on the retinal surface. It is generally been using this technique routinely age.
easily aspirated with back flush in removing pre-retinal blood when-
needle or an end opening extrusion ever vacuum-cleaning technique References
needle connected to active aspiration does not work before resorting to 1. Charles S. Vitreous microsurgery
module of the vitrectory machine forceps removal. Often times the
(Vacuum cleaning). 1,2 If the blood is technique does work obviating for- Williams & Wilkins, 1987, 83-84.
tenacious because of clotting, forceps ceps blood removal, which can be 2. O’Malley, C. Extrusion Method.
removal may be necessitated. traumatic to the retina or even cause
retinal tears. We believe hydraulic Octome fragmatome newsletter,
We experienced difficulty some- back pressure helps in breaking up 1987, 3.
times in removal of pre-retinal blood tenuous blood clot and hence sim-
with Vacuum cleaning technique. plifies its aspiration. Dr. Yog Raj Sharma
The our surprise when back flush Dr. R.V. Azad,
mechanism was actuated, blood of-
Dr. Deependra V. Singh
Dr. R.P. Centre, AIIMS, New Delhi

December, 2003 246 DOS Times - Vol.9, No.6

CURRENT PRACTICE

Phakic Intraocular Lenses

Namrata Sharma MD, Jeewan S. Titiyal MD, Nishant Taneja MBBS,
Rasik B. Vajpayee MS, FRCS (Ed)

Phakic intraocular lens Ø Corneas thinner than 500 Two types of foldable in- Fig.1: Phakic 6 IOL
(IOL) is any lens located be- microns traocular lenses in this group
tween the cornea and the include: Fig. 2: Vivarte
crystalline lens, which is left Ø Steep or flat corneas power we use Van der
undisturbed in the eye. Ø Topographic change sug- 1. Vivarte (Ciba Switzer- Heijde nomogram, which
land) and the Duet (Tekia, takes into account the spheri-
Anterior chamber phakic gestive of keratoconus USA) in one group and cal equivalent, the corneal
intraocular lenses have been 4. Endothelial cell den- power and the anterior
used since 1950s but the sur- sity: at least 2250-2500mm3. 2. ICARE (Corneal, chamber depth.
gical procedure failed due to 5. Pupil smaller than 6 France) and Acrysof (Alcon,
lack of microsurgery devices mm in scotopic luminance. USA) Surgical Technique
and poor understanding of 6. Stable refraction for at To implant an angle sup-
the endothelial function. In least 1 year Vivarte and Duet have a
1987, there was a comeback 7. Anterior chamber foldable optic (acrylic) of ported anterior chamber
of these lenses and today depth (excluding corneal 5.5mm and 2 haptics made phakic IOL , the following
phakic intraocular lenses are thickness) at least 2.8mm of PMMA with 3 points for steps are performed:
an important area of refrac- 8. Angle width at least 30 the angle fixation. The differ-
tive surgery. degrees ence between these two IOLs 1. Pre-operative miosis
9. No eye pathology ex- is that in the Duet the haptic 2. Incision size of 6.2 mm
Types of Phakic IOLS cept refractive and optic are implanted for Phakic 6 (corneal/
There are three types of 10. No systemic pathol- separately in the bag and the corneoscleral)
ogy such as diabetes, col- lens is assembled in the eye 3. Incision of 3.2mm
phakic IOLs. These include: lagen diseases etc whereas in the ICARE and (clear corneal self sealing )
1. Anterior chamber- Acrysof the folding occurs 4. Fill anterior chamber
Angle Supported Phakic outside the eye. with standard viscoelastic
angle fixated IOL e g. ZB M5, 5. Introduce the IOL
NuVita MA20, Phakic 6. IOLS Selection of angle sup- 6. No iridotomy / iridec-
First generation angle ported IOL tomy required
2. Anterior chamber- Iris 7. Wash out the vis-
fixated IOL e g. VerisyseTM supported IOLs were devel- To select an IOL we need coelastic
Phakic IOL (Artisan lens) oped by Baikoff & Joly in to calculate the power and 8. Suture in case of
1997. The first model (ZB - the size of the implant. As
3. Posterior chamber sul- DOMILENS) was a modified these IOLs are supported by
cus fixated IOL e g. STAAR Kelman type lens with a the angle and the size of the
Implantable contact lens and 4.0mm optic and 2 haptics anterior chamber varies
phakic refractive lens (PRL) with a 4-point fixationin the from patient to patient, the
angle. However, this lens correct size of the anterior
Selection of patients for had a high vault and was so chamber must be defined.
phakic IOLs close to the endothelium that Most surgeons measure hori-
it had to be explanted in 50 zontal or vertical white to
1. Age above 18 years % of the eyes due to endot- white with the help of the
2. Moderate to high helial damage. calipers, Holladay discs or
myopes (>-9.00D) & hype- Orbscan.
ropes (> 4.5 D) In the line of Kelman type
3. Also indicated in angle supported anterior To this white-to-white, a
lesser degrees of ametropias chamber phakic IOL, the correction factor is added to
if LASIK is contraindicated only available at present is determine the correct length.
such as PHAKIC 6which is made of For example 1 mm in Phakic
PMMA, has a 6.0mm optic 6, 0.5-1.0mm in Vivarte and
Cornea and Refractive Surgery and 2 haptics with four point 1.5mm in Acrysof.
Services, Dr. R.P.Centre for fixationin the angle.
Ophthalmic Sciences, AIIMS, To calculate the lens
New Delhi.

December, 2003 247 DOS Times - Vol.9, No.6

CURRENT PRACTICE

Fig.4: Nuvita lens 8. Iridectomy/ Iridoto-
my recommended
Fig. 3: Duet IOL Problems of anterior chamber phakic IOLs
9. Postoperatively, topi-
Phakic 6 IOL 1. Endothelial cell loss ® Intermittent endothelial cal steroids and antibiotics
9. Postoperatively, topi- touch are given for 1 week

cal steroids and antibiotics 2. Pupillary ovalisation (4-42%) The advantages of these
are given for 1 week a) Immediate post operatively ® Iris tuck/ over- lenses are as follows:
sized IOL
The problems, which b) Late onset ® Iris root ischemia 1. Enclavation of the loop
have been encountered with tips produce a pillow of iris
these lenses, are as follows: 3 Iris depigmentation(2.3-4.5%) ® Iris protrusion tissue over the most periph-
during surgery eral part of the haptics
Iris Supported Anterior
Chamber Phakic IOLS 4. Halos & glare® Small optic zones 2. The angle of the ante-
5. Surgically induced astigmatism® Long incisions rior chamber, the crystalline
Iris fixated IOLs have lens, and the corneal endot-
haptics in the form of lobster Selection of iris fixated IOLs 2. Two side ports are helium are not at risk be-
claw that fixate the IOL to the Concerning the power, made (2 mm away from each cause they are far away
mid peripheral iris. The clas- extremity of main incision)
sical type of this phakic IOL the rules are same as for an- 3. The Pupil can be dilated
is the Artisan (Ophtec, Neth- terior chamber fixated 3. Main incision 5.2 or 6.2 for fundus examination. Iris
erlands & Verisyse AMO). phakic IOLs. Concerning the mm) corneal or corneoscleral claw lens does not affect the
size: ' one size fits all' as these movements of the iris and the
The Artisan lens is a one- implants are not dependent 4. Fill the anterior cham- pupil, except at the point
piece UV wavelength ab- on the eye dimensions. ber with standard viscoelas- where the iris passes through
sorbing PMMA compression tic the claw. The crystalline lens
molded lens with a diameter Surgical Technique is not affected since the im-
of 8.5 mm. The optic is The steps of the surgery 5. Introduce the IOL planted lens remains far
vaulted suitably (0.5mm) to 6. Grasp the iris tissue away from it.
stay clear of the iris cone. It is are as follows: into the claws
available in 5.0mm optic (for 1. Pre-operative miosis 7. Wash out the vis- These lenses are very easy
myopia -3.00 to -23.00 and coelastic to explanted of needed new
hyperopia + 3.0 to +12.00) or lenses can be important any
6.0mm (available for myopia Problems of Iris fixated phakic IOLs increased risk.
-3.0 to - 14.50 D). There is also
a toric Artisan available in 1. Anterior chamber inflammation: early post-op- 6.4 Posterior Chamber Phakic
5.0mm model, which cor- to 16% of eyes (Fechner et al 1992) IOLS
rects upto astigmatism of -
7.00 D. Two models are avail- 2. Glaucoma In the years between 1990-
able: Model A: axis of cylin- 1998 a new material came
der in the axis of IOL and 3. Iris atrophy: on fixation sites - 81% cases( Santonja into vogue known as the
Model B: Axis of cylinder 90 et al) Collamer. This was a hybrid
degrees of the axis of IOL. of silicone and collagen and
4. Implant dislocation: lens instability & haptic the lens was called as the
disincarceration in 9.3% ( Santonja et al.) Implantable contact lens or
the ICL. The current version
5. Decentration : 23.4-56% (Manejo et al.) available is the V4, which
was introduced in 1998.
6. Endothelial cell loss: mean endothelial cell loss
5.3%, 7.63% &17.9% at 1, 2 &5 years respectively. Fig.5: Artisan lens Phakic
IOL (VerisyseTM)
7. Cystic wounds and subconjunctival fistulas- rare

December, 2003 248 DOS Times - Vol.9, No.6

CURRENT PRACTICE

the patient with the benefits Fig. 7: Staar ICL Collamer Fig. 8: PRL
of 'minimally invasive im-
Fig.6: Artisan lens Phakic plant surgery'. The current Problems of phakic posterior chamber IOLs
IOL (VerisyseTM) PRL has 2 tiny dots on the
haptics in order to avoid in- Ø Inverted implantation- iatrogenic
The PRL or the phakic re- verted implantation. Ø Endothelial cell damage (2.3-3.0% at 2 yrs)
fractive lens is another pos- Ø Inflammation
terior chamber phakic IOL 5. Smooth and gentle Ø Pigment dispersal
available with Ciba vision. It retro positioning of the Ø Elevated IOP
is made of new generation footplates involves maneu- Ø Cataractogenesis -0.82 to 4.38% at 5 years
ultra thin hydrophobic sili- vering the haptics through Ø Decentration
cone. It has no anatomical the 1 mm sideports with sand
fixation sites and floats on the blasted visco cannula or spe- naturally prone to posterior 2003 Sep;136(3):442-7.
layer of aqueous humor in- cifically designed 'tuckers'. segment disorders. Night- 4: Sanchez-Galeana CA, Smith
side the posterior chamber Bimanual irrigation aspira- time symptoms are frequent RJ, Sanders DR, Rodriguez FX,
exerting no traction on the tion is then done to remove but disabling only in a few. Litwak S, Montes M, Chayet AS.
ciliary structures and with- the viscoelastic agent. With latest and future gen- Lens opacities after posterior
out coming in contact with erations wide optic lenses chamber phakic intraocular
the anterior capsule of the Phakic Iols: Whre Are We and adequately sized lenses lens implantation. Ophthalmol-
crystalline lens. these problems including the ogy. 2003 Apr; 110(4):781-5.
Today? problem of cataractogenesis 5: El-Sheikh HF, Tabbara KF.
The Sticklens (IOLTECH, Roughly 60,000 phakic should decrease. Although Cataract following posterior
France) is available which is the short-term results are re- chamber phakic intraocular
made up of hydrophilic IOLs have been implanted assuring, the long-term re- lens. J Refract Surg. 2003 Jan-
acrylic material, which sticks (equally divided among sults are awaited. Feb;19(1):72-3.
firmly to the anterior surface angle fixated, iris supported 7: Sanders DR, Vukich JA; ICL
of the crystalline lens. and posterior chamber Sugested Reading in Treatment of Myopia (ITM)
phakic intraocular lenses. If 1: Guell JL, Vazquez M, Study Group. Incidence of lens
Surgical Technique properly sized and im- Malecaze F, Manero F, Gris O, opacities and clinically signifi-
1. To prevent angle clo- planted, all these phakic Velasco F, Hulin H, Pujol. J. Ar- cant cataracts with the implant-
IOLs are likely to produce tisan toric phakic intraocular able contact lens: comparison
sure 2 fully patent suffi- more or less the acceptable lens for the correction of high of two lens designs. J Refract
ciently wide Nd: YAG laser similar results in terms of astigmatism. Am J Ophthalmol. Surg. 2002 Nov-Dec; 18(6): 673-
iridotomies must be done 1 precision, predictability and 82.
to 2 weeks before surgery. stability of the refractive out-
come. The anecdotal inci-
2. Peripheral irido- dence of catastrophic events
tomies should be placed at like endophthalmitis and
11 and 1 0'clock under the retinal detachment is accept-
upper lid to avoid the risk of ably low if considered in
monocular diplopia, ghost terms of risk/benefit ratio in
images and for aesthetic rea- a population who is also
sons.
Summary of posterior chamber Phakic IOLs
3. Intraoperative surgi-
cal iridectomy is a less rec- Model ICL ( STAAR) PRL( CIBA Vision) Sticklens(IOLTECH)
ommended option. Optic
Geometry Single piece Single piece Single piece
4. Both ICL and PRL are Diametrs Planospherical Planospherical Meniscus
injected through a less than Material 5.5/5.25/5.0/4.6 5/4.5 6.5
2.5 mm incision to provide Special features Collamer Hydrophillic Silicone Hydrophillic Acrlic
Power Toric custom No No
-3 to –21 -3to-20 -7to-25
Power calc. Formula +3to+17 +3to+15 +4to+7
Incision size
Olson-Feingold Holladay Refractive Van der Hejide

2.5mm 1.8mm 3.0mm

December, 2003 249 DOS Times - Vol.9, No.6

CURRENT PRACTICE

Contrast Sensitivity Measurement orders: AMD, Diabetic ret-
inopathy, Glaucoma

and its Practical Implications 5. Optic neuritis
Methods

Parul Sony MD, Vandana Kori BSc Testing contrast sensitiv-
ity is important as it subjec-

tively assesses the patient’s

visual function in day to day

Contrast is created by the trast. The symbols of the vi- loss life. Various charts and elec-

difference in luminance, and sual acuity charts are close Snellen visual acuity Vs tronic devices are available

the amount of reflected light, to the maximum contrast. If Contrast sensitivity: Snellen’s to measure the contrast sen-

reflected from two adjacent the lowest contrast per- charts test VA at a very high sitivity. The key difference is

surfaces. It provides critical ceived is 5%, contrast sensi- contrast thus many patients target type. For example, the

information about the edges, tivity is 100/5=20. If the low- have a good snellens VA but Pelli-Robson chart deter-

borders and variation in the est contrast perceived by a they may be visually handi- mines the contrast required

brightness of two objects. It person is 0.6%, contrast sen- capped in real life situations. to read large letters of a fixed

can be defined with the fol- sitivity is 100/0.6=170. The VA drops in the situa- size. With the Pelli-Robson

lowing formula: Contrast sensitivity fun- tions with low contrast and chart, the contrast varies

Contrast = Lmax - Lmin ction (CSF) is defined as the the quality of vision is not while the letter size remains

Lmax + Lmin visual function that is mea- good. CS is a useful index of constant. The Regan chart, a

Lmax = Luminance on the sured using a range of sinu- pattern vision. It provides low-contrast letter chart

lighter surface soidal grating pattern as the the information that cannot having different size letters,

Lmin = Luminance on the visual stimulus. CS assesses be obtained from visual acu- reduces the contrast levels of

darker surface the patient’s sensitivity to ity, and it is often a better a standard Snellen-type let-

Contrast sensitivity is large, intermediate and predictor of visual perfor- ter acuity chart resulting in

the reciprocal of the contrast small objects (spatial fre- mance then VA. There are several charts. The Func-

at threshold, i.e., one di- quency) under the condi- various causes that may de- tional Acuity Contrast Test

vided by the lowest contrast tions of varying contrast. It crease the CS uses sine-wave gratings.

at which forms or lines can is a subjective measurement 1. uncorrected refractive Most common stimulus

be recognized. If a person of a person’s ability to detect errors, used for the clinical evalua-

can see details at very low a low contrast pattern 2. keratoconous tion of spatial CS is repeti-

contrast, his or her contrast stimuli and it gives a more 3. cataract tive patterns of alternating

sensitivity is high and vice accurate representation of 4. posterior segment dis- light and dark bars where

versa. Contrast sensitivity the eyes’ visual perfor-

measures the ability to see mance. The CSF usually de- Contrast sensitivity is the reciprocal of
details at low contrast levels. creases with age especially
the contrast at threshold, i.e., one
Depending on the structure for high and intermediate

of the stimulus used in the spatial frequencies. A low divided by the lowest contrast at which
measurement - either grat- CSF reduces the amount of
ings of different size or sym- detail that can be seen espe- forms or lines can be recognized.

bols - contrast sensitivity of cially in lower levels of light-

a person gets different val- ing or at a distance like, dif-

ues. When the darker sur- ficulty in reading poor con-

face is black and reflects no trasting print materials, dif-

light, the ratio is 1. Contrast ficulty in moving around

is usually expressed as per- safely in dim light. The

cent, then the ratio is multi- pathological loss of CS is of

plied by 100. The maximum four types

contrast is thus 100% con- 1. generalized loss at all

frequencies

Dr. R.P.Centre for Ophthalmic 2. high frequency loss Fig. 1: Cambridge low contrast charts
Sciences, AIIMS, 3. mid frequency loss
New Delhi. 4. low-mid frequency

December, 2003 250 DOS Times - Vol.9, No.6

CURRENT PRACTICE

Plate no Contrast % l Bailey Lovie chart varying contrast. Thus there quencies. It is an accurate
l Vision contrast test are two contrast levels in and comprehensive grating
Demo 13 system (VCTS) by each row. The illumination chart that tests functional
1. 5 Vistech of the chart is 85 cd/mm2 visual acuity. The chart tests
2. l Cambridge low con- and glare should be avoi- five spatial frequencies
3. 2.7 trast grating ded. The test is carried at a (sizes) and nine levels of
4. 1.6 l Regan charts distance of 1 meter with pa- contrast. The Contrast var-
5. l FACT charts tient wearing the best cor- ies in a row, decrease from
6. 1 rection and before dilating left to right. And the spatial
0.72 the pupils. The patient is frequencies increase as one
0.52 asked to read the alphabets move down the various col-
starting from left hand cor- umns from top to bottom.
7. 0.37 Cambridge low con- ner, when he fails to respond This test is performed at a
several seconds are given to distance of 10 feet. The pa-
8. 0.27 trast gratings him to retry and guess the tient determines the last
alphabet. The score of the grating seen for each row (A,
9. 0.19 It is a rapid and test is recorded by the faint- B, C, D and E) and reports
10. 0.14 simple screening test for est triplet out of which at the orientation of the grat-
least 2 letters are correctly ing: right, up or left. The last
contrast sensitivity. Per- identified. The log CS value correct grating seen for each
for this triplet is given by the spatial frequency is plotted
formed at a distance of on a contrast sensitivity
Contrast curve. FACT contrast sensi-
6m. It comprises of 12 sensitivity tivity scores can also be used
measures the ability to generate images with
pair of plates consisting to see details at VSRC’s EyeView™ Func-
low contrast levels tional Analysis Software
of stripes of varying con- which demonstrates how
number on the scoring pad the world looks to your pa-
trast. First one is for nearest to the triplet, either tient based on their contrast
on the left or the right side. sensitivity scores. FACT
demonstration and rest Each eye is tested separately Contrast Sensitivity Charts
and then the both eyes to- are available in two sizes:
are for the proper testing gether. The three measure-
ments should not take Studies have shown that
and are numbered from longer then 8 minutes. Usu- the contrast sensitivity curve
ally the binocular log CS is provided by sine-wave grat-
1-10. The plates are higher by 0.15 units then ing tests is more sensitive
monocular CS. However de- and informative than the re-
changed sequentially velopment of cataract may sults obtained from low-
result in poorer binocular CS contrast letter acuity sys-
starting from plate 1 till when compared to the CS of tems. Pelli Robson is more
each eye being tested sepa- sensitive and most repro-
the patient fails to re- rately. ducible methods for study-
Functional Acuity Contrast ing and detecting the mid
spond. Then a new se- Testing (FACT) range loss of CS.

ries is begun starting 4 FACT charts were devel- Practical application
oped by Dr. Arthur Gins- Importance of CSF lies in
plates prior to where the burg. FACT comprises of a
chart with sine-wave grat- various practical situations
patient failed to re- ings of varying contrast as like:
well as varying spatial fre- l Driving in winter in fog
Fig. 2: Pelli robson contrast sensi- spond. Four such series
tivity charts and scoring pad are completed and the or rain
score of each series is l Radiographic diagnosis
l In near vision tasks like
the luminance of the bars noted (numbered as per

varies sinusoidally along the the number of plate read)

single axis (known as sine and added. The final total

wave grating). The patient value is converted into con-

signals when the pattern is trast sensitivity from the

first detected. Typically the provided table.

spatial frequency varies

from 0.5 to 23 cpd. The PELLI ROBSON contrast

graphic representation of sensitivity charts

the mean and standard de- This chart utilizes letters

viation of the threshold of of the same size but with re-

different spatial frequencies ducing contrast to provide a

is called the CS curve or CSF. quick means of assessing

The CS peaks around 4 cpd patient contrast sensitivity.

of spatial frequency. Con- There are two charts and

trast sensitivity measures two scoring pads. The two

the ability to see details at charts have different letter

low contrast levels. The vari- sequence but other wise

ous methods available to they are similar. Each chart

measure CS include has 6 letters in each row or-

l Pelli Robson test ganized into two triplets of

December, 2003 251 DOS Times - Vol.9, No.6

CURRENT PRACTICE

Fig. 3: FACT chart Monthly Meetings Calendar
For The Year 2003-2004
Distance FACT Chart and Near FACT Chart
27th July, 2003 (Sunday)
Cambridge Pelli FACT Army Hospital
low contrast robson
gratings 30th August, 2003 (Saturday)
Stimulus Alphabets Contrast Sir Ganga Ram Hospital
type Contrast gratings
gratings 1m 10 feet 27th September, 2003 (Saturday)
Test distance 85-150cd/ — Hindu Rao Hospital
Luminance 6m mm
100cd/mm2 1 chart 1 near, 19 October, 2003 (Sunday)
1 distance DOS Midterm Conference
Number of 12 chart
Plate 1st November, 2003 (Saturday)
R.P. Centre for Ophthalmic Sciences
reading and writing, if the have poorer CS when
information is at low con- compared to the mono- 29th November, 2003 (Saturday)
trast focal IOL especially for Dr. Shroff’s Charity Eye Hospital
l In every day tasks, where near vision
there are numerous visual l The aspheric IOL (Tec- 27th December, 2003 (Saturday)
tasks at low contrast, like hnis) provides a signifi- Venu Eye Hospital & Research Centre
cutting an onion on a light cant improvement in reti-
colored surface, pouring nal image contrast. This 31st January, 2004 (Saturday)
coffee into a dark mug, improvement is signifi- Safdarjung Hospital
checking the quality of cantly better when com-
ironing, etc pared to the performance 28th February, 2004 (Saturday)
l Development of cataract of conventional spherical M.A.M.C. (GNEC)
causes a decrease in the silicone and acrylic IOLs.
contrast sensitivity. The l CS decreases after refrac- 28th March, 2004 (Saturday)
CS shows improvement tive surgery like RK, PRK Mohan Eye Institute
after the cataract surgery. and LASIK. Lasik has the
Various IOLs have differ- least effect on CS, though 3-4th April, 2004 (Saturday & Sunday)
ent effect on the postopera- it has been seen that CS im- Annual DOS Conference
tive CS. The CS recovery proves slightly still it does
is best with all PMMA not return to baseline even Attention DOS Members
IOL>Acrylic IOL> silicone by 6 months postopera-
IOL tively. The Hi-tech DOS Library has started functioning on
l Diffractive multifocal IOL Ground Floor, Dr. R.P. Centre, Delhi Ophthalmic Sci-
ences, AIIMS, New Delhi-110029 from 12.00 Noon to
9.00 P.M. on week days and 10.00 A.M. - 1.00 P.M. on
Saturday, Sunday. The Library will remain closed on
Gazetted Holidays. Members are requested to utilise
the facilities available i.e. Computer, Video Viewing,
Latest Books and Journals. We are planning to sub-
scribe two journals. Member can give suggestion in this
regard.

Dr. Lalit Verma

Library Officer, DOS

December, 2003 252 DOS Times - Vol.9, No.6

MANAGEMENT PEARLS

Analysis of Problem Situations:

Management of IOL Power Calculation Problems
After Refractive Surgery

Sudipto Pakrasi MD, DNB

These days, cataract pa- readings from the standard large area. Rather than mea- rately determining the
tients who have previously intraocular lens formulas suring several points within keratometric power. Man-
undergone refractive proce- are inaccurate for these pa- a central 2.5 to 3.5 mm area, ual and automated kerato-
dures are taking center stage tients. the measurement may in- meters evaluate the radius
in many ophthalmic prac- stead be at 6.0 mm. With the of curvature designated by
tices. As the popularity of re- Conventional manual non-incisional forms of four points in orthogonal
fractive surgeries such as keratometry measures a lim- keratorefractive surgery, meridians separated about
LASIK and PRK grows, sur- ited number of points at a 3 such as LASIK and PRK, the 3.2 mm apart with manual
geons will increasingly be to 4 mm annulus, which can index of refraction of the cor- keratometers, or about 2.6
confronted with the prob- vary with steeper or flatter nea is probably changed. mm apart in automated
lem of calculating the proper corneal shapes. Another fac- Automated keratometry keratometers. Corneal optics
IOL power after previous tor introduced by corneal and corneal topography in keratometers is assumed
corneal refractive surgery. tissue removing surgeries, analysis therefore use incor- to be spherocylindrical. Nor-
Surgeons are dancing as fast such as LASIK, has been the rect assumptions in measur- mal corneas are nearly
as they can to try to avoid change in the standardized ing corneal power. The cor- spherical, or prolate. A pa-
all-too-common refractive refractive index of the cor- nea can no longer be com- tient who, prior to the refrac-
surprises in these patients. nea due to the change in the pared to a sphere centrally. tive surgery, is myopic is
Postrefractive surgery pa- corneal power of the front The back surface is no longer going to have a relatively
tients often bring with them corneal surface. 1.2mm steeper than the front flatter cornea in the center
the same high expectations surface. The reading mea- and it’s going to get steeper
they had for their refractive Why a problem? sure the curvature at 3mm. in the periphery. Postre-
procedures. They’re going to The true corneal power This may not reflect the fractive corneas, however,
want the same sort of visual power in the centre of the are oblate.
outcomes after cataract sur- following RK, ALK, PRK cornea. In normal corneas
gery that they achieved af- and LASIK is difficult to the posterior curvature of Setting The Stage For
ter refractive surgery. This measure by keratometry, or the cornea is 1.2 mm less Trouble
requires a different ap- corneal topography. The than the anterior surface.
proach from that used with reasons for this are as fol- Anterior corneal radius of For these reasons,
the typical cataract patient. lows: 7.5 mm, using the Standard- keratometry, and corneal
ized Keratometric Index of topography will typically
The difficulty of IOL Keratometry and topog- Refraction of 1.3375, the cor- over-estimate central cor-
power calculation after re- raphy assume a normal re- neal power would be 45 D. neal power following kera-
fractive surgery lies in the lationship between the ante- Overestimates total power torefractive surgery for
ability to accurately calcu- rior and posterior corneal by 0.56 D. Most IOL calcu- myopia. For low power my-
late corneal powers. The al- curvatures and measure the lations today used a net in- opic corrections by RK (less
tered corneal shape can re- anterior corneal radius. dex of refraction of 1.3333 than -2.00 D), this effect is
sult in multiple ranges of Keratorefractive surgery for (4/3) and the anterior radius minimal. But for higher
corneal power throughout myopia flattens the anterior of the cornea to calculate the power myopic corrections,
the central corneal surface. corneal radius, but leaves net power of the cornea. Us- and especially those by
The average keratometric the posterior corneal radius ing this total power of a cor- LASIK, this over-estimation
mostly unchanged. This dis- nea = 44.44 D. The major can be quite significant. Fail-
Eye Microsurgery Associates parity is greater with LASIK source of IOL error in such ure to keep this important
Aashlok Hospital, Safdarjung and somewhat less with RK. patients therefore is accu- fact in mind will often result
Enclave, New Delhi Because the central cornea in an unexpected and un-
has been flattened, kerato-
metry may read a falsely

December, 2003 253 DOS Times - Vol.9, No.6

MANAGEMENT PEARLS

K Value Problems Figures: ractive keratectomy. The term keratometric di-
(A) Normal Cornea (Fig A) Corneal thickness - reduced opters are used to avoid con-
Direct Change of Central fusion with optical diopters,
B) AFTER PRK/LASIK (Fig B) Anterior Corneal Curvature since keratometric diopters
w Anterior curvature changed and optical diopters are not
w Posterior curvature - No change During excimer laser equivalent. There are a num-
photorefractive keratectomy ber of formulas available for
C) AFTER RK (Fig C) (PRK), selective removal of the calculation of IOL
w Anterior & posterior - similar changes tissue across the anterior cor- power. They can be classi-
w No change of corneal thickness neal surface results in a fied as either empirical re-
change of the anterior cor- gression formulas (most
pleasant post-operative hy- steeper in the center and flat- neal curvature. Although the popular are the Sanders-
peropic surprise. ter in the periphery. Practi- central anterior surface of the Retzlaff-Kraff formulas)
tioners are going to be mea- cornea may become flatter with (SRK/T) or without
With the postmyopic re- suring keratometry values (to treat myopia) or steeper (SRK I and II) the inclusion
fractive laser in-situ from the flatter part of the (to treat hyperopia), the pos- of additional terms account-
keratomileusis patient, this cornea and estimating low. terior surface is presumed to ing for non-linearity or theo-
means the practitioner will Therefore, IOL power will remain stable. The same may retical optical formulas
be measuring the be overestimated and prac- be true for uncomplicated (Holladay, Hoffer, or
keratometry values from the titioners will get a myopic laser in situ keratomileusis Haigis).
steeper part of the cornea surprise. Potentially adding (LASIK) in which direct flat-
rather than the centrally flat- to the error is the fact that tening or steepening of the There are five variables in
tened portion. The K is go- manual and automated central anterior corneal sur- such a formula:
ing to estimate high, so keratometers don’t take into face is achieved by focal kera-
you’ll estimate your IOL account irregular astigma- tectomies under a 1) Intraocular lens
power to be lower than it tism, which may occur after planohinged flap. power, which is generally
should be, and you’re going radial keratotomy, or central chosen as the dependent
to get a hyperopic surprise. islands and decentrations Indirect Change of Central variable;
In post-hyperopic LASIK with LASIK or photoref- Anterior and Posterior Cor-
patients, the corneas are neal Curvature 2) Keratometric diopt-
ers (average keratometry
To correct myopia with reading)—the most crucial
radial keratotomy (RK), variable after refractive cor-
deep radially oriented inci- neal surgery;
sions are applied in the
midperiphery of the cornea 3) Axial length, mea-
to induce midperipheral sured by A-scan ultrasonog-
bulging of the cornea. Indi- raphy or by optical means;
rectly, the central cornea be-
comes flatter. Since no tissue 4) Effective lens posi-
is removed it is assumed tion; and
that the anterior and poste-
rior surfaces of the cornea 5) Target refraction, typi-
react in an analogous way. cally ranges between -2.00
and 0 diopters (D).
Principles In Intraocular
Lens Power Calculation Calculation of the result-
ing spectacle correction for
Calculation of intraocular a given IOL is typically
lens (IOL) power in cataract based on a vertex distance of
surgery is based on mea- 12 or 14 mm. The only vari-
surements of corneal able that cannot be mea-
power/radius of curvature, sured preoperatively is the
axial length, and estimation effective lens position. Im-
of postoperative anterior provements in IOL power
chamber depth—termed ef- calculations over the last 30
fective lens position (ELP). years are mainly a result of
improving the predictability
of effective lens position by
additional measurement of
horizontal white-to-white

December, 2003 254 DOS Times - Vol.9, No.6

MANAGEMENT PEARLS

corneal diameter, preopera- K = Preoperative Average K - Change in Manifest Reac- ract will be eliminated. Any
tive anterior chamber depth, tion Prerefractive and Postrefractive Surgery glare from the kerato-
and lens thickness, since the refractive procedure will re-
anterior segment dimen- Ktrue = Kpre + Rpre – Rpost main unchanged.
sions often are not propor- Generally holds true, if the following are known:
tional to the axial length n Ktrue = the true corneal power after refractive surgery How to Deal with the Prob-
n Kpre = the average corneal power in diopters before re- lem?
Types of Formulae fractive surgery, and 1. Measuring K
n Rpre = the spherical equivalent in diopters before re- w A) Manual Keratometry
1. Regression Formulas fractive surgery, and w B) Automated Kerato-
These are based upon n Rpost = stable spherical equivalent in diopters after re- metry
mathematical analysis of a fractive surgery, then w C) Corneal Topography
large sampling of post-op- 2. Calculating K
erative results. Most famil- To give accurate information, the refractive numbers (Rpre w A) Clinical history
iar is SRK formula: works and Rpost) must retain their corresponding plus (hyperopic) method
well 22.5 to 25.0 mm in axial and minus (myopic) signs, and be corrected for vertex dis- w B) Contact Lens method
length. The formula does not tance. w C) Double K method
work well for “long” (>25 3. Other methods
mm) or “short” (<22.5 mm) K = Base Curve + (Difference in Refractive Error with- w Intraoperative Retinos-
eyes. out Contact Lens and with Contact Lens) copy
w Hand held Autorefrac-
2. Theoretical Formulas Ktrue = Cbase + Cpower + Rcl - Rbare tometers
Theoretical formulas are Generally holds true, if the following are known: w Secondary IOL Implant
l Ktrue = the true corneal power after refractive surgery w Piggyback IOL
optical formulas based on the l Cbase = base curve of the contact lens in diopters, and w IOL Exchange
optical properties of the eye. l Cpower = spherical refractive power of the contact lens
They do a better job of pre- in diopters, 1. Measuring K:
dicting post-op outcomes for l Rcl = spherical equivalent refractive error with the Methods to Assess
long and short eyes.3 widely contact lens, &
used theoretical formulas, l Rbare = spherical equivalent refractive error without the Keratometric Diopters as A
each with their own contact lens, then Measure of Central Corneal
strengths and weaknesses. To give accurate information, the refractive numbers ( Rcl Power
These formulas are included and Rbare) must retain their corresponding plus (hyperopic)
in various and minus (myopic) signs, and be corrected for vertex dis- Keratometry
combinations with many A- tance. 1. A) Manual-Manual
scan instruments. They are
also available in software · Gaussian Optics For- first three help evaluate the keratometry is the method
products mula amount of irregular astig- that IOL power calculation
· Holladay between 22 and No matter what type of matism, which may be con- formulas were originally
tributing to the reduced vi- based upon. Keratometry
26mm [refractive] procedure the sion, as well as the cataract. evaluates only four points
· Hoffer Q shorter than patient has had, the stability The irregular astigmatism separated 3 to 4 mm in two
of the refraction must be de- may also limit the patient’s orthogonal meridians on the
22.5mm termined. This determina- vision after cataract surgery. paracentral cornea, and the
· SRK/T for long eyes tion includes daily fluctua- The endothelial cell count corneal optics are assumed
tions from morning to night, can identify patients with to be spherocylindrical.
(>26mm). as well as long-term changes. low cell counts from the pre- Thus, asphericity or asym-
… Each of these factors must vious surgery who may be metry of corneal shape can-
3. Recent Developments be used in determining the at a higher risk for corneal not be measured with stan-
· Holladay II Tackles se- desired postop target refrac- decompensation or pro- dard keratometry.
tion and to prepare the pa- longed visual recovery. Sec-
vere myopia tient for the visual changes ondary tests include the po- Manual keratometry
· Holladay Consultant and realistic expectations tential acuity meter, super probably represents the least
after the procedure. pinhole, and hard contact accurate method since cur-
IOL program – (HIC) lens trial. In addition, pa- rent instruments, such as the
uses Holladay 2 formula In these patients, use tients should be informed Zeiss, Javal- Schiötz, or
(uses7 variables) biomicroscopy, retinoscopy, that only glare from the cata- Bausch & Lomb kerato-
· New Haigis formula corneal topography, and en-
optimised for axial length dothelial cell counts. The
dependency of the type of
IOL to be used

December, 2003 255 DOS Times - Vol.9, No.6

MANAGEMENT PEARLS 256 DOS Times - Vol.9, No.6

meters make too many as-
sumptions that do not take
into account irregular cor-
neal astigmatism. Neverthe-
less, the examiner is actually
able to see the reflected
mires and the amount of ir-
regularity. Seeing the mires
does not help get better mea-
surements, but does allow
the observer to discount the
measurement as unreliable.

1. B) Automated-Auto-
mated keratometers may be
more accurate than manual
keratometers in corneas af-
ter RK that have small clear
zones (i.e., less than 3 mm)
because they sample a
smaller central area of the
cornea (nominally 2.6 mm).
The smaller the clear zone
and the greater the number
of RK incisions, the greater
the probability and magni-
tude of error. This error oc-
curs because the samples at
2.6 mm are close to the para-
central transition zone
(knee) after RK. After PRK
or LASIK, automated
keratometers accurately
measure the front radius of
the cornea, because the tran-
sition areas are far outside
the 2.6- mm zone that is
measured. However, deri-
vation of keratometric di-
opters from the radius of
curvature is still wrong.

1. C) Corneal Topogra-
phy Analysis

w Videokeratography
derived Simulated Kerato-
metry Readings (Sim-K) -
using the topography sys-
tem, the simulated kerato-
metry value (Sim-K) is de-
termined from the power of
Placido mires 7, 8, and 9 of
the videokeratoscope for 128
equally spaced meridians.
Measuring more than 5000
points over the entire cornea

December, 2003

MANAGEMENT PEARLS

and more than 1000 points mined. Two scanning slit 2B) Contact Lens Method
within the central 3 mm, lamps project 40 calibrated
videokeratography pro- beams onto the eye, angled The current refraction = +0.25 D.
vides greater accuracy in at 45° to the left and to the With a plano hard contact lens BC of 35 D placed on the
determining the power of right of the video camera
corneas with irregular astig- axis, covering the whole cor- cornea, the spherical refraction changes to -2 D. Because the
matism compared to kerato- nea from limbus to limbus patient had a myopic shift with the contact lens, the cornea
meters. However, Sim-K and overlapping in the cen- must be weaker than the base curve of the contact by 2.25 D.
value derivation may vary tral 5-mm zone. This system
among different video- has the potential to provide Therefore, the cornea must be 32.75 D (35 - 2.25), which is
keratoscopes, and these val- topographical height and slightly different than the value obtained by the calculation
ues should be compared to power maps of the anterior method.
the results of conventional and posterior corneal sur-
keratometry before using face as well as a corneal SEQ refraction without hard contact lens = +0.25 D
them interchangeably. thickness profile, allowing a Base curve of plano hard contact lens = 35.00 D
direct correlation of SEQ refraction with hard contact lens = -2.00 D
w Average Central pachymetry and height Change in refraction = -2.00 - (+0.25) = -2.25 D (myopic
Power (ACP) - A new pa- data. shift)
rameter, average central Mean corneal power = Base curve of plano HCL + change
power, from the average of 2. Calculating K: in refraction
corneal powers inside the Combination of the clini- Mean corneal power = 35.00 + (-2.25)
region demarcated by the Mean corneal power = 32.75 D
entrance pupil of the TMS-1 cal history & contact lens
videokeratoscope. Because methods are considered the 2 B) Contact lens method Postrefractive K readings
the density of measured most accurate ways of deter- (Overrefraction) : are at the center of the prob-
points with the videokera- mining the IOL power after lem. However, no matter
toscope is highest in the cen- refractive surgery. It should After refracting the pa- how flat the cornea gets af-
tral cornea and decreases be remembered that these tient, a plano hard CTL with ter refractive surgery, the an-
toward the periphery, area- methods will give an estima- known base curve is placed terior chamber depth does
corrected power was used tion of the true central cor- on the eye and an over-re- not change. After corneal re-
for compensation. This neal power and may not be fraction is performed. If the fractive surgery, the distance
modified method is sup- exact. At present, these tech- refraction does not change from the cornea to the in-
posed to have major advan- niques represent the best with the lens, then the power traocular lens must remain
tages over the classic Sim-K clinical methods available. of the cornea must be the similar. Therefore, instead of
after RK with small clear Hopefully, in the future we same as the base curve of the using postrefractive surgery
zones, but not after PRK and may have a more accurate, CTL. If there is a myopic K values alone, which will
LASIK. and less time-consuming, shift, the power of the base lead to inaccurate results,
method for measuring these curve is greater than that of they should be paired with
Other similar values are challenging eyes. the cornea by the amount of the original preoperative K-
provided by other videoke- the shift. If there is a hyper- value for the first step of the
ratoscopes. For example, the 2. A) Clinical history opic shift, the power of the calculation. Practitioners are
EyeSys videokeratoscope method base curve of the CTL is less advised to use the
has a display called the than that of the cornea by the postrefractive K-value for
Holladay Diagnostic Sum- Requires the following in- amount of the shift. This the remaining calculation —
mary in which there is an formation: works only if visual acuity is in effect splitting the K val-
analogous value calculated Ø Pre-Refractive refraction better than 6/24. ues.
called effective refractive Ø Pre-Refractive K readings
power. Ø Post-Refractive refraction 2 C) Double K method Each of these methods
A new method for calcu- will assist the cataract sur-
w Scanning Pancorneal (preferably current, but geons to more accurately
Slit Topography -Using the before significant cataract lating postrefractive IOL select the proper IOL power
Orbscan scanning slit-beam formation). power, developed by Jaime for patients who have had
videokeratoscope , a three- Using K reading before Aramberri, MD, (Spain), previous corneal surgery.
dimensional location of sev- and after refractive surgery, uses a modified SRK-T for- The most difficult challenge
eral thousand points of the refraction derived K is cal- mula. With these standard for refractive surgeons is that
corneal and anterior cham- culated at the corneal plane, calculations, in postre- much of the data necessary
ber surfaces can be deter- and used in the IOL formula. fractive surgery patients, a are often not present because
hyperopic refractive error is of the long time interval be-
the rule. tween a patient’s cataract

December, 2003 257 DOS Times - Vol.9, No.6

MANAGEMENT PEARLS

surgery and refractive sur- these refractions should not edema. Daily fluctuations patient has realistic expec-
gical procedure. A working be relied upon, however, for cause a myopic shift during tations.
knowledge of these three ba- fine-tuning the IOL power. the day (due to the regres-
sic methods combined with Factors such as the pressure sion of corneal edema after 2. Make sure that the re-
trying to gather as much pre- from the lid speculum, axial awakening in the morning). fraction is stable (after re-
operative patient informa- position of the IOL, intraocu- fractive surgery and before
tion as possible, will help lar pressure may cause the Long-term Results after RK cataract surgery), before you
surgeons overcome this intraoperative refraction to Long-term results of cata- take up the patient for sur-
problem, which will cer- be different than the final sta- gery.
tainly grow in significance as bilized postoperative refrac- ract surgery are very good.
the number of patients re- tion. If the intraoperative re- The long-term hyperopic 3. Discuss the desired
ceiving refractive surgery fraction is within 2 D of the shifts and against-the-rule target refraction. Aiming for
increases worldwide. target refraction, no lens ex- astigmatism over time fol- -1.00 D seems to be a good
changes should be consid- lowing cataract surgery compromise. Do remember
The first two methods, ered unless intraoperative should be the same as fol- that trying to produce
the clinical history method keratometry can also be per- lowing RK. Glare and monovison in a patient who
and hard contact lens formed. starburst patterns are usu- has never experienced this
method, can be used for ally minimal - adjusted to condition may cause intoler-
incisional surgery as well as Ø 3C) Secondary IOL Im- these unwanted optical im- able anisometropia and may
excimer laser surgery. Care plant: After completing the ages following the initial require further surgery.
must be taken with the to- initial surgery, IOL can be RK. If the patient’s primary
pographic method when implanted at a secondary complaint before cataract 4. Perform corneal topog-
analyzing patients who stage. surgery is glare and raphy analysis in all pa-
have had previous PRK or starbursts, it should be made tients, in case you have ac-
LASIK due to a change in Ø 3D) Piggyback IOL: clear to the patient that only cess to it, to assess the
effective refractive corneal Another IOL can be placed the glare due to the cataract amount of irregular astig-
index of refraction. in the sulcus after the pri- will be eliminated by sur- matism and asphericity.
mary IOL implantation after gery, and the symptoms that
In the future, our ability 3 – 6 months, when the re- are due to the RK will re- 5. If keratometric diopt-
to more accurately measure fraction stabilizes. main unchanged. ers and refraction before re-
the corneal surfaces includ- fractive surgery are known,
ing the anterior and poste- Ø 3E) IOL Exchange: The Post Myopic LASIK use the clinical history
rior curvature, as well as most drastic way out can be Center flatter & periph- method, considering the
new IOL technologies that undertaken, in case the pa- change of spherical equiva-
may allow for more surgeon tient is miserable with the ery steeper, hence, the vari- lent refraction at the corneal
customization will help us initial results. ous methods measure K plane after RK, PRK, or
improve the accuracy of this from steeper part of cornea LASIK. If those values are
difficult postrefractive sur- Results after PRK/ LASIK causing higher K values, not known, you may want to
gical situation. Very few results of cata- giving rise to lower IOL use the respective calcula-
power estimates making the tions at the spectacle plane
1. Other Methods ract surgery following PRK person HYPERMETROPIC. to be on the safe (ie, myopic)
Ø 3A) Intraoperative Reti- and LASIK are available. Post Hypermetropic LASIK side. Some experts in this
field even recommend the
noscopy: Hyperopic shift on the Center steeper & periph- use of spherical equivalent
Ø 3B) Hand held Autoref- first day and daily fluctua- ery flatter hence, the various refraction change at the
tions appear to be much less, methods measure K from spectacle plane routinely
ractometers: These intraop- similar to the early postop- flatter part of cornea causing and add another 1.00 to 2.00
erative measures may be uti- erative period following lower K values, giving rise D to the resulting IOL
lized to reconfirm the IOL these procedures. In most to higher IOL power esti- power, being sure to avoid
power calculated in the pre- cases, the stability of the cor- mates making the person any potential undercorre-
operative examination. nea makes these cases no MYOPIC. ction. The clinical history
different than patients who method seems to be the most
Large refractive surprises have not had keratore- Summary & Practical Rec- reliable method after RK,
can be avoided by intraop- fractive surgery. ommendations PRK or LASIK.
erative retinoscopy or
handheld autorefractors. Be- Postoperative after RK 1. Just like you do before 6. If keratometric diopt-
cause there are many factors First Postoperative Day – every refractive surgery pro- ers but not refraction before
at surgery that may change cedure, make sure that the refractive surgery is known,
in the postoperative period, Leads to hyperopic shift, use the change in anterior
due to the transient corneal

December, 2003 258 DOS Times - Vol.9, No.6

MANAGEMENT PEARLS

surface keratometry read- operative days following neal curvature separately af- or LASIK may be realized by
ings after PRK or LASIK. their RK. This is due to cor- ter PRK or LASIK. This can entering the measured value
neal edema. These patients be achieved by means of into an empirical quadratic
7. If preoperative kera- may also exhibit diurnal fluc- scanning slit topography, regression formula. Cer-
tometric diopters and re- tuations of refraction during although the accuracy of the tainly, such a theoretical ap-
fraction are not known and the early time period after Orbscan unit for posterior proach must be refined after
the visual acuity is 6/24 or cataract surgery. No lens ex- corneal curvature measure- clinical data become avail-
better, try the hard contact change should be contem- ments has not yet been fully able from more cataract op-
lens method after RK. plated until the refraction validated. However, mea- erations.
has stabilized (1 week to 3 suring the accuracy of an in-
8. If preoperative kera- months). strument on posterior curva- At this time, no definite
tometric diopters and re- ture is not possible since the statement can be made con-
fraction are not known and 11. Following PRK and true shape of these surfaces cerning IOL power calcula-
visual acuity is less than 6/ LASIK, early hyperopic shift cannot be referenced. tion in patients with intra-
24 or plano hard contact or diurnal fluctuations ap- corneal rings. However, re-
lenses are not available, use pear to be much less after However, to be on the safe versing the refractive corneal
average central power or the cataract surgery. In most side, refractive surgeons effect by timely removal of
average keratometric diopt- cases, stability of the cornea might consider giving their the ring before assessment of
ers at multiple paracentral makes these cases no differ- patients a wallet card indi- keratometric diopters might
cursor points of video- ent than patients who have cating their preoperative be a valid option. This seems
keratography after RK, but had no previous refractive keratometric reading, preop- even more reasonable in the
use refined calculation of corneal surgery. erative refraction, and post- face of the multiple reports
keratometric diopters from operative refraction at some about complete reversibility
radius of anterior and poste- Future Challenges stable time point to allow for of the refractive effect after
rior corneal surface after In many situations today, the application of the clini- ring removal.
PRK or LASIK. cal history method.
patients may ask for cataract The foolproof methodol-
9. Use more than one surgery in centers other than An additional approach ogy has not yet been discov-
modern third-generation those where the refractive to adjust keratometry read- ered as yet. Since the prob-
formula (Hoffer Q, Holladay procedure has been per- ings after PRK and LASIK lem is made more complex
2, SRK/T, Haigis). Do not use formed. Thus, neither the may be to apply multiple re- by the fact that there are dif-
a regression formula (SRK I preoperative keratometry gression analysis comparing ferent types of refractive sur-
or SRK II) to calculate the IOL reading nor the exact amount the corrected keratometric geries, the non-availability of
power and choose the high- of refractive correction may diopters to the measured val- most of the pre refractive
est value for your implant. be available. ues and to the spherical data, we have to wait for
equivalent refraction change accurate solutions to be de-
10. During the first days In these eyes, it might be a in a large number of cases. veloped – till then; the above
after cataract surgery follow- good option to consider the Thus, correction of kera- mentioned suggestions may
ing RK, patients may experi- keratometric diopters of the tometric diopters after PRK be followed.
ence a significant hyperopic anterior and posterior cor-
shift similar to the first post-

Attention DOS Members

Applications are invited for DOS Fellowship for partial financial
assistance to attend international conference(s). The last date for
receiving application is 31st January 2004.

For details please see page no. 263.

December, 2003 259 DOS Times - Vol.9, No.6

MANAGEMENT PEARLS

Management of Common Intra-Operative
Complications of Phacoemulsification

Sarmi Malik MS, AK Grover MD, FRCS

Phaeoemulsification is a may block the tip and lead to adjacent conjunctiva bal- planned. In case of very large
technically demanding sur- its clogging. Therefore, some loons up, making the proce- detachments transcorneal
gery with often a long learn- amount of viscoelastic must dure more difficult. If the sutures may be required.
ing curve. Complications, be aspirated before starting side port incision is too big,
especially in the early stages the irrigation. Wound burns there will be continuous Problems with the rhexis
of the learning curve are not lead to high astigmatism and leakage. In such cases, it is In order to achieve the
uncommon, which gradu- inadequate wound closure. advisable to place a suture
ally reduce to make it an ex- Sometimes, they may even and continue after making a perfect rhexis, there has to be
tremely safe procedure. necessitate suturing. new side port incision. good visibility (good illumi-
However, one must be aware nation and magnification)
of all the possible complica- 2) Wound leak Descemet’s detachment and a chamber filled with
tions, so as to minimize their An inadequate corneal Descemet’s detachment viscoelastic. The patience of
occurrence and to manage the operating surgeon is of
them competently, should valve is responsible for may occur during phacoe- utmost importance during
they arise. The complications wound leak. As mentioned mulsification by the follow- this part of the procedure. A
of phacoemulsification may good viscoelastic material
occur at any stage of the pro- Descemets detachment occurs due to such as Sodium hyduranate
cedure. the use of blunt instruments in the (Healon) is very helpful. Me-
anterior chamber, accidental injection of thyl cellulose, if cooled has a
Problems related to the in- viscoelastic under the Descemet’s mem- greater viscosity, which
cision brane or attempted insertion of an IOL helps in capsulorhexis. The
1) Wound burn through an incision that is too small. most common problem dur-
ing rhexis is extension into
A wound burn is caused above, a wound burn may ing ways. It may be due to the periphery. This can be
by excess heat energy at the also cause a wound leak. Hy- the use of blunt instruments managed by using a fine for-
phaco tip. The vibrations of dration of the anterior lip of in the anterior chamber, ac- ceps. The advancing edge is
the titanium tip, while caus- the incision as advocated by cidental injection of vis- grasped and pulled sharply
ing emulsification of the Fine, may help to close the coelastic under the Des- inwards. (Fig. 1 & 2) It can
nucleus, also produce a tre- incision. In case the wound cemet’s membrane or at- also be managed by making
mendous amount of heat in still leaks despite hydration, tempted insertion of an IOL a cut in the intended direc-
the anterior chamber even it is prudent to place sutures. through an incision that is too tion of the rhexis, using a fine
exceeding 100 degrees cen- small. The management in scissors. Following this, the
tigrade. This heat leads to 3) Induced astigmatism such a case would depend on rhexis is completed using
swelling of the superficial Postoperative astigma- the extent of detachment. If forceps.
corneal stroma and thus its the detachment is small, one
opacification. Some of the tism may be avoided by us- can proceed with the Management of a small
risk factors include hard ing either a temporal incision phacoemulsification, taking pupil
nucleus, more phaco power, or an incision place in the care not to cause further
a tight wound and insuffi- steeper axis of preexisting damage. In case of larger de- Performing a phacoemul-
cient irrigation (too low astigmatism. tachments, it can be reat- sification procedure in a pa-
flow). Viscoelastic agents tached using air or viscoelas- tient with a small pupil poses
Problems with the side port tic and depending on the special difficulties during
Vision the Eye Clinic, If the side port incision is situation, the surgery may be rhexis and greater chances of
12/27, West Patel Nagar, postponed or continued as iris damage. Therefore, the
New Delhi-8 made too close to the limbus, pupil size must be increased
it impinges on the iris. The using non-surgical or surgi-
cal means. Non-surgical

December, 2003 260 DOS Times - Vol.9, No.6

MANAGEMENT PEARLS

methods include viscomyd- downwards. It can be pre- the stage of early nuclear vitrectomy may be done de-
riasis (injection of viscoe- vented by the following phaco, viscoelastic is injected pending on the location of
lastics into the anterior cha- methods. The phaco proce- beneath the nuclear frag- the nuclear material. How-
mber), pharmacological dure must only be carried out ment until the fragment ever, if the nuclear material
treatment and the use of iris in the central 5-6mm zone, comes into the anterior is posteriorly located, a total
hooks. Viscoelastics produce the rhexis should never be chamber. Under cover of vis- vitrectomy is done followed
a mechanical mydriasis. crossed, the phacoprobe coelastic, phaco may be done by one of the following op-
should always be parallel to in the anterior chamber tions:
Pharmacological mydria- the iris and the bevel of the while using a Lens glide.
sis is produced by instilling probe should be pointed Alternatively, the incision a) Perflorocarbon liq-
intracameral preservative- upwards. may be enlarged and the uids are used to float up the
free adrenaline through a nuclear fragment brought nucleus and subsequently
side port incision. It is used Rupture of the posterior out. remove it. It is very impor-
in a concentration of I ml of capsule tant that the PFCL should be
1: 1000 that is diluted in 10ml 2) Rupture with vitreous loss completely removed at the
of BSS. The most popular iris Some principles are to be The remnants of the end of the procedure. The
hooks are De Juan and followed as soon as posterior disadvantages of using
Mackool hooks. De Juan capsule rupture is detected. nucleus are extracted manu- PFCL besides the high cost
hooks consist of segments in ally with the help of a for- include requirement of a
monofilament nylon threads a) Stop working as soon ceps or gentle phaco after third port and possible toxic
that are curved at one end. A as the problem is detected. injecting viscoelastic under effects on the retina.
silicone device is fitted at one the fragments and coaxing
end to block the hook at the b) Maintain a closed them into the anterior cham- b) A phacofragmenter is
desired length. Hooks are chamber ber. Alternatively, the inci- used to fragment the nucleus
inserted through a paracen- sion may be extended and within the vitreous and sub-
tesis site and after retracting c) Preserve as much of the fragments removed us- sequently remove it.
the iris, are blocked by the the posterior capsule as pos- ing a wire vectis and a
silicone device. Usually four sible. spatula. A large fragment c) The nucleus may be
hooks are used to create a may be removed using the speared and brought up into
square shaped pupil. (Figure Three possible situations sandwich method, in which the anterior chamber with
3,4,5) Mackool hooks consist include a wire vectis is used below the help of light from an
of titanium and are already and an iris repository is used endoilluminator.
blocked at a preset distance. 1) Rupture without vit- above to take out the entire
Surgical methods of increas- reous loss fragment. Suggested reading
ing the pupil size include
sphincterotomy, pupillo- 2) Rupture with vitreous Depending on the size of 1) Textbook of Ophthalmology
plasty, midperipheral iridec- prolapse the opening and the amount Volume 3. Eds Sunita
tomy, radial iridectomy and of vitreous loss, a vitrectomy Agarwal, Athiya Agarwal,
keyhole iridectomy. The dis- 3) Rupture with disloca- is performed using an ante- David J Apple, Lucio
advantages of these surgical tion of nuclear material into rior or a posterior approach. Buratto, Jorge L Alio, Suresh
maneuvers include bleed- the vitreous At the end of irrigation and K Pandey and Amar
ing, postoperative inflam- aspiration, an anterior Agarwal
mation, iris traction and 1) Rupture without vitreous vitrectomy is done.
sometimes the need to leave loss 2) Phacoemulsification- Prin-
permanent ins sutures in 3) Rupture with dislocation ciples and Technique. Lucio
situ. This occurs most com- of nuclear material into the Buratto
monly during the stage of ir- vitreous
Iris injury rigation and aspiration. 3) Phacoemulsification, Laser
Iris injury may be due to Once it is detected, the illu- In such a situation, it is al- Cataract Surgery and Fold-
mination and magnification ways wise to let an experi- able IOLS. Eds Sunita
performance of the proce- of the microscope should be enced vitreoretinal surgeon Agarwal, Athiya Agarwal,
dure in a patient with a small increased. The anterior cha- take over. The vitrectomy Mahipal Singh Sachdev,
pupil, shallowing of the an- mber is filled with an air performed may be anteriorly Keiki R Mehta, Howard
terior chamber or facing the bubble or viscoelastic and limited if the nuclear mate- Fine, Amar Agarwal
bevel of the phacoprobe the probe is removed at the rial is limited to the anterior
same time in order to main- portion. A limited 4) Advances in Ophthalmol-
tain the anterior chamber. A ogy 1. Ashok Garg, Suresh
dry aspiration using a one- K. Pandey, Vidushi Sharma,
way cannula is done. The David J. Apple.
one-way cannula is attached
to a syringe containing BSS.
In case the rupture occurs at

December, 2003 261 DOS Times - Vol.9, No.6

“International Symposium on Uveitis and Intraocular Inflammations”
and “3rd Annual Conference of Uveitis Society of India”

February 6 – 8, 2004, Venue : PGIMER, Chandigarh

FACULTY

1. Dr Narsing A Rao, USA 15. Dr D.N. Shah, Nepal
2. Dr Anita Agarwal, USA 16. Dr J Biswas, Chennai
3. Dr Janet Davis, USA 17. Dr S.R. Rathinam, Madurai
4. Dr Carl P Herbort, Switzerland 18. Dr S.P.Garg, New Delhi
5. Dr Marc de Smet, The Netherlands 19. Dr V.S.Sangwan, Hyderabad
6. Dr Tran Van Tao, Switzerland 20. Dr Alay Banker, Ahmedabad
7. Dr Manfred Zierhut, Germany 21. Dr Vinita Rao, Jalna
8. Dr Ilknur Tugal Tutkun, Turkey 22. Dr M.R.Dogra, Chandigarh
9. Dr Manabu Mochizuki, Japan 23. Dr Jagat Ram, Chandigarh
10. Dr Khalid F Tabbara, Saudi Arabia 24. Dr Sunil Arora, Chandigarh
11. Dr James E Puklin, USA 25. Dr P.Bambery, Chandigarh
12. Dr Ahmed M Abu EI-Asrar,S Arabia 26. Dr Vishali Gupta, Chandigarh
13. Dr Luca Cimino Oculista, Italy 27. Dr Amod Gupta,Chandigarh
14. Dr Peizeng.Yang, China

HIGHLIGHTS

Plenary Sessions: VKH Syndrome, Serpiginous Choroditis and Ocular Tuberculosis
Updates: Comprehensive Coverage of Uveitis and Intraocular Inflammation
Current techniques: Diagnosis, Investigations, Pharmacotherapy and surgery

· Interactive case presentations by International Faculty
· Free paper Narsing A Rao Award

Free paper submissions are invited from all 100 words abstract may be
e-mailed to the Organising Secretary before 30.12.2003.

Registration Fee: Upto 30.11.2003 After 1.12.2003 Spot
Delegates Rs 800/- Rs 1000/- Rs 1200/-
Students Rs 600/- Rs 800/- Rs 1000/-

For more details contact:

Dr Vishali Gupta, Organising Secretary, Department of Ophthalmology,
Postgraduate Institute of Medical Education and Research, Chandigarh 160 012.

Telefax: 0172-2747837, E-mail: [email protected]

December, 2003 262 DOS Times - Vol.9, No.6

Delhi Ophthalmological Society Fellowship for Partial
Financial Assistance to Attend Conferences

Conferences Points Awarded
International: Two fellowships per year (two fellowships can
be awarded at a time if committee feels that papers are very 1) Age of the Applicant Points
good)
· Maximum of Rs. 25,000/- per fellowship will be sanctioned a) £ 35 years 10

National: Three fellowships per year (only for AIOS) b) 36 to 45 years 07
· Maximum of Rs. 5,000/- per fellowship will be sanctioned
c) 45 years plus 05
Eligibility:
· DOS Life Members (Delhi Members only) 2) Type of Presentation
· 75 or More DCRS Points
· Accepted paper for oral presentation, poster, video or in- a) Instructor/ Co-instructor of Course 12

struction course. b) Free Paper (Oral) / Video 07

Time since last DOS Fellowship: c) Poster 05
Preference will be given to member who has not attended
3) Institutional Affiliation
conference in last three years. However if no applicant is found
suitable the fellowship money will be passed on to next year. a) Academic Institution 15
Members who has availed DOS fellowship once will not be
eligible for next fellowship for a minimum period of three b) Private Practitioner 20
years.
4) DCRS Rating in the immediate previous year
Authorship
The fellowship will be given only to presenting author. Pre- a) 75-150 05

senting author has to obtain certificate from all other co-au- b) > 150 08
thors that they are not attending the said conference or not
applying for grant for the same conference. (Preference will c) < 75 not eligible for fellowship
be given to author where other authors are not attending the
same conference). If there is repeatability of same author group Documents
in that case preference will be given to new author or new
group of authors. Preference will also be given to presenter · Proof for age. Date of Birth Certificate
who is attending the conference for the first time.
· Original / attested copy of letter of acceptance of paper for
Quality of Paper
The applicant has to submit abstract along with full text to oral presentation / video / poster or instruction course.

the DOS Fellowship Committee. The committee will review · Details of announcement of the conference
the paper for its scientific and academic standard. The paper
should be certified by the head of the department / institu- · Details of both International & National Conferences at-
tion, that the work has been carried out in the institution. In
case of individual practitioner he or she should mention the tended in previous three years.
place of study and give undertaking that work is genuine. The
fellowship committee while scrutinizing the paper may seek · Copy of letter from other national or international agency
further clarification from the applicant before satisfying itself
about the quality and authenticity of the paper. Only Single / agencies committing to bear partial cost of conference if
best paper has to be submitted by the applicant for review (6
copies). Quality of the paper will carry 50% weightage while any.
deciding the final points.
· At least one original document should be provided, that is
Poster and Video
The applicant will need to submit poster and video for re- ticket, boarding pass or registration certificate along with

view. attendance certificate of the conference.

Credit to DOS · Fellowship Money will be reimbursed only after submis-
The presenter will acknowledge DOS partial financial as-
sion of all the required documents and verified by the com-
sistance in the abstract book / proceedings.
The author will present his or her paper in the immediate mittee.

next DOS conference and it will be published in DJO/DOS · Undertaking from the applicant stating that above given
Times.
information’s are true.

· If found guilty the candidate is liable to be barred for fu-

ture fellowships.

Dr. J C Das (President DOS), Dr. Gurbax Singh (Vice Presi-

dent DOS), Dr. Kamlesh (Editor) Dr. Lalit Verma (Library Officer),

Dr. Sudipto Pakrasi (Member) and Dr. Jeewan S. Titiyal (Secretary

DOS) will be the members of DOS Fellowship for Partial Fi-

nancial Assistance to Attend Conferences Committee.

Application should reach Secretary’s office addresses to

President DOS before 31st July and 31st January for interna-

tional conference and before 30th September for national con-

ference. The committee will meet thrice in a year in the month

of August, October and February with in 2 weeks of last date

of receipt of applications. The committee will reply within four

week of last date of submission in yes/no to the applicant. No

fellowship will be given retrospectively, that means prior sanc-

tion of executive will be necessary.

Dr. Jeewan S. Titiyal, Secretary

Delhi Ophthalmological Society

R.No. 476, 4th Floor,

Dr. R.P. Centre for Ophthalmic Sciences

AIIMS, Ansari Nagar, New Delhi – 110029

December, 2003 263 DOS Times - Vol.9, No.6

REVIEW

Ophthalmic Viscosurgical Devices and Anterior Segment Surgery:

Surgical Applications and Complications

Suresh K. Pandey M.D., Jaya Thakur M.D., Liliana Werner MD Ph.D., David J. Apple M.D.

Background The viscoelastic sodium hy- gery using phacoemu- 4- It should give a good cap-
Viscoelastic substances aluronate was first used in lsification with IOL implan- sular flap control, provid-
ophthalmic surgery in 1972, tation. Some of these details ing the soft and perma-
are solutions with dual when it was introduced as a are shown in the schematic nent spatula effect.
properties; they act as vis- replacement for vitreous photograph (Figures 1, 2).
cous liquids as well as elas- and aqueous humor. Since Cleavage of lens structure
tic solids or gels. The ideal then ophthalmic surgical Capsulorhexis It is best performed with
viscoelastic substance in procedures had undergone In order to perform an in-
ophthalmology should be considerable advancement. the use of OVDs. The ideal
viscous enough to prevent The use of viscoelastic ma- tact and successful capsu- viscoelastic material keeps
collapse of the anterior terials has become common- lorhexis, the contents of the the anterior chamber shape
chamber at rest, yet liquid place in anterior and poste- anterior chamber have an unchanged during BSS® in-
enough to be injected pre- rior segment surgeries. important role. Till date bal- jection and also avoids in-
cisely through a small can- These agents facilitate deli- anced salt solution (BSS®), crease in pressure, which
nula. It should be elastic or cate and often difficult in- air and OVDs have been can be produced with exces-
shock absorbing and should traocular manipulations used. Out of these three the sive amount of BSS® known
enhance coating yet has during various ophthalmic best is viscoelastic as it is as capsular blockade.
minimal surface activity. It considered the easiest, saf-
should be cohesive enough Nuclear emulsification
to be removed easily from OVD should be viscous enough to During phacoemulsifi-
the anterior chamber but not prevent collapse of the anterior chamber
so cohesive that it is aspi- at rest, yet liquid enough to be injected cation, the viscoelastic is
rated during irrigation and likely to remain in the ante-
aspiration, which would precisely through a small cannula. It rior chamber instead of leak-
provide no protection to en- should be elastic or shock absorbing ing out of the eye (Figure
dothelial cells during surgi- and should enhance coating yet has 2C). OVDs help in preserv-
cal manipulations. It should ing the space and also be-
be eliminated from the eye minimal surface activity cause of their low cohesive-
in the postoperative period ness, they remain in the an-
without any effect on in- surgical procedures. est, and the most reproduc- terior chamber despite high
traocular pressure. ible method in both routine irrigation flow. Moreover
Surgical Application of the and difficult cases (Figures OVDs adhere to the corneal
Viscosurgery was a term OVDs 2A, 2B). To perform a good endothelium, thus protect-
coined by Balazs to describe capsulorhexis, the viscoelas- ing the corneal endothelial
the use of these solutions In recent years the field of tic to be used should have cells. Healon® and Healon-
that had viscous, elastic and viscosurgery has broadened the four basic features- GV® does not trap the air
pseudo plastic properties rapidly. It has been used 1- High molecular weight bubble and provide excel-
during and after surgical both intraocularly as well as lent endothelial protection
procedures. During visco- extraocularly, which in- and high viscosity at zero (Figure 2D). This is because
surgery, viscoelastic sub- cludes cataract, cornea, shear rate, which main- of-
stances are used as a fluid or glaucoma, viteroretinal, tains the anterior cham- 1- Scavenger effect- This ef-
a soft surgical instrument. strabismus and oculoplastic ber.
surgeries. 2- Excellent visibility pro- fect captures the free radi-
Moran Eye Center, Department of vided by high transpar- cals released during
Ophthalmology and Visual Use of OVDs in Cataract ency. phaco with consequent
Sciences, Fifth Floor, University of Surgery 3- Make surgical maneuvers inactivation.
Utah, 50 North Medical Drive Salt easy, due to high elastic- 2- Binding sites- There are
Lake City, Utah-84132, USA. OVDs are helpful in each ity and pseudoplasticity. chemical receptors for
step of modern cataract sur- viscoelastic materials on

December, 2003 264 DOS Times - Vol.9, No.6

REVIEW

the corneal endothelium. Fig.1A: Injection of the viscoadaptive OVD in the anterior cham- tic nature of ocular tissues.
A molecular bond seems ber through a 25 G cannula. It is difficult to perform a
to occur between the vis-
coelastic solution and the Fig.1B: Capsulorhexis is in progress. good capsulorhexis in the
corneal endothelium. presence of high capsular
3- High Elasticity- This also Fig.1C: Phacoemulsification in progress. elasticity. Moreover there is
smoothes the possible im- low scleral rigidity, greater
pacts of the lens material like the adult surgery has present and future, Third intravitreal pressure that
against the endothelium. undergone major changes in Prize for “Special Interest”, makes the capsulorhexis
The phaco tip being in a recent years with the evolu- Annual Video Festival, XXth even more difficult, as the
closed system, its vibrations tion of techniques including Congress of the European pressure tends to curve the
are transmitted to the inter- small incision and the devel- Society of Cataract and Re- capsulorhexis. But with the
nal structures of the eye but opment of modern IOLs fractive Surgeons, Nice, use of viscoelastic, e.g.
viscoelastic provides a (Wilson ME, Pandey SK, France, September 2002). Healon-GV® the effective
smothering shield against Werner L, Apple DJ. Pediat- The main principle lies in push is in the opposite direc-
them. ric cataract surgery: Past, the control of the very elas- tion and hence completion
of capsulorhexis can be
Irrigation and aspiration done.
The role of viscoelastic
In pediatric cases, the
during this procedure is the capsulorhexis must be
protection of the endothe- started in the central portion
lium. This is possible due to and not towards the equator,
high adhesiveness. It re- in order to prevent radial
mains where it is placed, extension. The high density
without mixing with the cor- viscoelastic agents stabilize
tex because of its low cohe- the posterior chamber and
siveness thus helping in easy push back the vitreous face
removal of cortex. during the posterior capsu-
lorhexis. During IOL im-
Capsular bag filling and plantation, the capsular bag
IOL implantation is kept open and the anterior
chamber is well formed thus
During IOL implantation, ensuring easy and safe im-
it is necessary to expand the plantation of the IOL in the
capsular bag with a vis- bag. These agents also help
coelastic. It allows the sur- to dilate the pupil thus
geon to keep the bag well maintaining a good intraop-
opened and formed thus al- erative mydriasis.
lowing the easy IOL implan-
tation. OVD is also helpful OVDs like Healon-GV®
in correct positioning, cen- can easily be removed at the
tering and allowing for pos- end of the surgery including
sible IOL rotation maneu- the position which is behind
vers (Figs. 1E, 1F). Beside the IOL due to its high co-
posterior chamber IOL im- hesiveness thus preventing
plantation, OVD has also capsular blockade.
been used for implantation
of other IOL designs (e.g. Use of the OVDs in Glau-
anterior chamber, iris fix- coma Surgery
ated, artisan lenses, etc.) (Fig. Viscocanalostomy
2).
Viscocanalostomy is a
Cataract Surgery in Pediat- new surgical procedure for
ric Cases glaucoma therapy. Viscoe-
lastics play an important
Pediatric cataract surgery role in this procedure. Fig-
ure 3 illustrates the surgical

December, 2003 265 DOS Times - Vol.9, No.6

REVIEW

Fig.1 D: Viscoadaptive OVD is transparent and easy to see during removal (left). Note the pres- Schlemn’s canal. There is
ence of the air bubbles within the anterior chamber after use of dispersive viscoelastic solution also a communication thro-
(right). ugh the Descemet’s mem-
brane with the anterior
Fig.1 E: Implantation of a posterior chamber intraocular lens in vented and also the related chamber.
the capsular bag. discomfort with it. It mini-
mizes the risk of late infec- The OVDs should have
tions and is independent high pseudoplasticity to al-
from conjuntival and epis- low injection into Schlemn’s
cleral scarring. canal through a small needle
and should have high vis-
Viscocanalostomy allows cosity at shear rate of zero
the aqueous to leave the eye, to maintain the spaces as
through Schlemn’s canal long as possible. Healon-
and episcleral veins thus re- GV® and Healon-5® are
storing the natural outflow viscoelastics of choice for
pathway. This procedure this procedure.
creates a bypass by which
aqueous humor reaches OVDs for Intraocular Deliv-
Schlemn’s canal, skipping ery of Dyes or Anesthetic
the trabecular meshwork. A Agents
chamber is produced inside
the sclera, which is in direct Researchers and vision
communication with the scientists have been using
OVDs as a vehicle to deliver
capsular dyes for use during
cataract surgery. Mixing
these substances with the
viscoelastic agent was at-
tempted to prolong their ef-
fect and to limit the adverse
effect on ocular tissues. Ciba
Vision Corp. (Duluth, GA,
USA), has recently proposed
mixing an OVD with
lidocaine.

This was termed “viscoa-

Fig.1 F: Removal of the viscoadaptive OVD using irrigation-as-
piration tip.

steps of viscocanalosotomy. decreased risk of infection, Fig. 2: Beside posterior chamber IOL fixation in the capsular bag,
Viscocanalostomy literally and decreased incidence of OVDs can also be used for implantation of the various phakic and
means “opening of the canal cataract, hypotony and flat aphakic IOL designs in the anterior chamber, ciliary sulcus etc.
by means of viscoelastic sub- anterior chamber as the an- Use of the OVD facilitated the implantation of the Artisan® IOL as
stance”. This procedure is a terior chamber is not ope- shown in this photograph. (Courtesy: Camil Budo, M.D.).
non-penetrating and inde- ned, and moreover, with the
pendent from external filtra- absence of external filtration
tion. The advantages are the bleb formation is pre-

December, 2003 266 DOS Times - Vol.9, No.6

REVIEW

Fig.3. Surgical steps of viscocanalosotomy. (Courtesy: Dr. Med. Tobias Neuhann, M.D., Munich, Germany).

Fig.3.A: Deep block construction incision. Fig.3.B: Cutting the deep block in a single Fig.3.C: Proximal to Schlemm’s canal
plane with a spoon blade. there is a subtle change in the scleral fi-
bers, from a crossing pattern to a tangen-
tial pattern, with an increased opacity.

Fig.3.D: Descemet’s window. Fig.3.E: Cannulating Schlemm’s canal Fig.3.F: Tight closure suture of the flap.
with three puffs of viscoelastic directed at
the osteum.

nesthesia” and was intended ough removal of the OVDs tive Surgery, Seattle, WA, noted with Healonâ . The in-
to prolong the anesthetic ef- from the capsular bag and April 1999). crease in pressure can be se-
fect of intracameral the anterior chamber of the vere and prolonged, if the
lidocaine, as a complement eye is must after the end of Complications of OVDs: material is not thoroughly
to topical anesthesia. Also, the surgery. This is impor- OVDs have many posi- removed at the end of the
the steps of intracameral in- tant to avoid complications surgery. The rise in pressure
jection of OVDs and of such as rise in intraocular tive attributes but their occurs in the first 6 to 24
intracameral injection of pressure, crystallization of drawbacks and complica- hours and resolves sponta-
lidocaine, as a complement the IOL surface. Studies tions must be given careful neously within 72 hours
to topical anesthesia, would have shown that complete considerations. Some of the postoperatively. The rise in
be combined in only one step. removal of viscoelastic ma- important complications are pressure is due to the me-
terial from the capsular bag as follows- chanical resistance of the tra-
Removal of the OVDs can be more difficult when becular meshwork to the
Several techniques have some hydrophobic acrylic 1. Increase in intraocular large molecules of the vis-
lenses are used because of pressure coelastic material, which de-
been reported in the litera- the IOL’s tacky surfaces Increase in intraocular creases the outflow facility.
ture for removal of the (Apple DJ, Auffarth GU, Hence to decrease the inci-
OVDs. These include: Rock Pandey SK. Miyake poste- pressure is the most impor- dence of this complication,
and roll technique, two- rior view video analysis of tant postoperative complica-
compartment technique and dispersive and cohesive tion of OVDs. It was first
bimanual irrigation/aspira- viscoelastics, video pre-
tion technique. sented at the Symposium on Increase in intraocular pressure is the
Cataract, IOL, and Refrac- most important postoperative
We would like to empha- complication of OVDs.
size that a careful and thor-

December, 2003 267 DOS Times - Vol.9, No.6

REVIEW

many have advocated re- luxation following hydrod- Suggested Reading: ogy. Jaypee Brothers, New
moving and aspirating the issection), early postopera- Delhi, India, 2000, PP 325-330.
viscoelastic material from tive (originally described 1. Arshinoff SA, Opalinski YAV, 437-440, 378-384.
the eyes at the end of the sur- CBS), and late postoperative Ma J. The pharmacology of 6. Saini JS, Pandey SK. Advances
gery. (CBS with liquefied after- lens surgery: ophthalmic vis- in techniques of penetrating
cataract or lacteocrume- coelastic agents. In: Yanoff M, keratoplasty. In: Nema HV,
2. Capsular block syn- nasia). Ducker JS, eds, Ophthalmology. Nema N, eds., Recent Advances
drome or capsular bag St Louis, Mosby-Yearbook, in Ophthalmology, Volume IV,
distension syndrome Recently use of high-den- 1998; 4:20.1-21.6 Jaypee Brothers, New Delhi,
Capsular block syndrome sity viscoelastic agents, such India, 1998, pp 37-51
as Healon-GV®, has been 2. Pandey SK, Thakur J, Werner 7. Pandey SK, Thakur J, Werner
(CBS), is a newly described found to be associated with L, Sharma V, Izak AM, Apple L, Izak AM, Apple DJ. Classi-
complication of cataract-IOL complication of late CBS. DJ. Ophthalmic viscosurgical fication, clinical applications
surgery. It is characterized Main ingredient of the trans- devices: An update. In: Garg and complications of oph-
by accumulation of a lique- parent liquid in capsular A, Pandey SK, Sharma V, thalmic viscosurgical devices:
fied substance within a bags is sodium hyaluronate Apple DJ, eds., Advances in An update. In: Garg A, Pandey
closed chamber inside the and that the distention is Ophthalmology. Jaypee Broth- SK, eds., Textbook of Ocular
capsular bag, formed be- caused by aqueous humor ers, New Delhi, India 2003, (in Therapeutics. Jaypee Brothers,
cause the lens nucleus or the being drawn into the capsu- press). New Delhi, India 2002, PP:
posterior chamber IOL optic lar bag by an osmotic gradi- 392-407
occluded the anterior capsu- ent across the capsule when 3. Liesegang TJ. Viscoelastics. 8. Pandey SK, Wilson ME, Apple
lar opening created by the the capsulorhexis diameter Surv Ophthalmol 1990; 34:268- DJ, Werner L, Ram J. Child-
capsulorhexis. Depending is smaller than that of the PC 293 hood cataract surgical tech-
on the time of onset, CBS is IOL and by viscoelastic ma- nique, complications and
classified as intraoperative terial retained and trapped 4. Pandey SK, Werner L, Apple management. In: Garg A,
(CBS seen at the time of lens in the bag intraoperatively. DJ, et al. Dye-enhanced pedi- Pandey SK, eds. Textbook of
atric cataract surgery. J Pediatr Ocular Therapeutics. Jaypee
Ophthalmol Strabismus 2003 (in Brothers, New Delhi, India
press). 2002, PP 457-486.

5. Ram J, Pandey SK. Anesthe-
sia for cataract surgery. In:
Dutta LC. Modern Ophthalmol-

REQUIRED

Full time In Glaucoma
Ophthalmologist
for a upcoming Perimetry: Basics, single field and followup.
Interpretation, analysis and application in
Eye Hospital day to day clinical situations .
in
Newer imaging techniques : basics and
East Delhi interpretation : Utility in diagnosis and
followup
Contact : Dr. Sanjay Bajaj
A-1/1, Nathu Colony Chowk, Groups of Ten Each
Shahdara, Delhi – 110093 On Sunday :
Ph : 9810623636, 9810015012
December 14, 2003
February 8, 2004

Contact:
Dr. Devindra Sood
Glaucoma Imaging Centre
P-13, South Extension Part II
New Delhi 110049
Tel: (011 ) 26257803 : 26252000

December, 2003 268 DOS Times - Vol.9, No.6

REVIEW

Macular Function Tests letter subtends 5 minutes of 3. The pupil is scanned
visual angle on the retina. until the fringe pattern is
Each component of this let- seen.

Neena Kumar MD, Raj Vardhan Azad FRCS(Ed) ter subtends 1 minute at this 4. The patient is asked to
distance. indicate the orientation of the
bands of light.
Other methods of visual
5. Initially, large grat-
Macular function tests are b. Electrooculography acuity testing in cases of clear ings are used and then they
are gradually diminished
required for diagnosing as (EOG) ocular media are Landolt C until the patient is unable to
detect their correct orienta-
well as for following up of c. Visually evoked re- chart, grating acuity and tion.

macular diseases and for sponse (VER) Optokinetic Nystagmus (in 6. The potential visual
acuity is estimated from the
evaluating the potential children). Laser Interferom- width of the gratings.

macular function in eyes Psychophysical Tests etry and Potential Visual Laser generated fringes
are not dependent on the op-
with opaque media such as Visual Acuity acuity Meter (PAM) are used tical components of the eye
for focusing. Therefore,
cataract and dense vitreous Visual acuity measure- to measure visual acuity, if ametropia has little influence
on the patterns produced by
hemorrhage. The retinal ment is the most common media is opaque due to cata- retina. It also over predicts
the visual potential in
function testing can be di- test of foveal function. The ract, vitreous hemorrhage amblyopic eyes because la-
ser fringe vision is better than
vided into psychophysical best-corrected visual acuity etc. the letter acuity.

and physiologic methods. A is a measure of actual foveo- The Potential Visual Acu-
ity Meter (PAM)
psychophysicaltestissubjec- lar function. Visual acuity is Laser Interferometry
PAM projects standard
tive. A physical stimulus is measured by the visual reso- Laser Interferometry can Snellen chart through a small
clear area of an immature
presented to the patient and lution of a letter, symbol or a be used in eyes with imma- cataract; it is most accurate
in eyes with visual acuities
the patient indicates verbally pattern. The smaller the vi- ture cataracts.1 The resolving of 6/60 or better.2,3 The main
components of the PAM are
or by other subjective means sual angle subtended by the power of the macula is tested an incandescent light source,
a miniature transilluminated
his detection of the stimulus. parts of the test letter cor- by using two coherent beams Snellen chart and a +12 D
lens. In performing the test
Physiologic methods are ob- rectly seen by the observer, of light, which create a three the pupils should be widely
dilated and the patient is
jective. A stimulus is pre- the better the resolution of dimensional fringe pattern asked to read the letters on
the chart.
sented and a response pa- his visual apparatus. An- on the retina. The beams pro-
Pupillary reactions
rameter is measured by elec- otherfactor,whichaffectsthe duce two point sources be- The pupillary reactions

trophysiological or other should be normal even in the
presence of a mature cata-
means. Laser interferometry over-predicts the ract. The defect usually indi-
cates either a lesion of the
Psychophysical tests visual potential in amblyopic eyes optic nerve or extensive reti-
1. Visual acuity because laser fringe vision is better nal disease.
2. Pupillary reactions
3. Photostress test than the letter acuity.
4. Amsler grid
5. Two point discrimination visual acuity, is contrast. hind the lens opacity; the
test Contrast is defined as the light waves emitted from
6. Entoptic phenomenon difference in the luminance these two points overlap.
7. Testsdependentonmacu- between dark and light parts Where the crest of one wave
lar pigment of the test area divided by the overlaps the trough of the
8. Maddox rod test mean luminance. other, the effect is cancelled
9. Color vision and a black band is pro-
10. Foveal flicker sensitivity The Snellen chart duced. Where crests or
11. Grating psychophysics The Snellen score is ex- troughs coincide with one
12. Dark adaptation another, the enhancement
13. Perimetry pressed as a fraction. The produces bright bands of
numerator is the test distance light. The test is performed
Electrophysiologic tests and the denominator is de- as follows:
a. Electroretinography termined by the size of the
smallest letter correctly iden- 1. The pupils are widely
(ERG) tified. The numerical value dilated.
of the denominator is the
Dr. R.P.Centre for Ophthalmic distance at which the height 2. The light beam is di-
Sciences, AIIMS, of this smallest identified test rected into the center of the
New Delhi. pupil in the plane of the iris.

December, 2003 269 DOS Times - Vol.9, No.6

REVIEW

Photostress Test The chart is to be viewed light) is pressed firmly Haidinger’s brushes and the
Photostress test can differ- in modest light monocularly against the exterior of the eye Maxwell spot.
at a distance of 28-30 cm uti- through closed lids, the ar-
entiate visual loss caused by lizing the correct refraction borizing pattern of retinal Haidinger’s Brushes
macular disease from that for this distance. Viewing blood vessels can be made This test is commonly
caused by an optic nerve le- should be accomplished briefly visible. This test is
sion.4 The test is a gross ver- without previous ophthal- used as test of retinal func- used as a screening test for
sion of the dark adaptation moscopy and without instil- tion. retinal pathology in strabis-
test in which the visual pig- lation of any drugs affecting mus patients with amblyo-
ments are bleached by light. papillary size or accommo- The blue field Entoptic Phe- pia. If one views a diffusedly
This causes a temporary state dation. The test is performed nomenon (Flying spots) illuminated source of plane-
of retinal insensitivity, which as follows: polarized white or blue light,
is perceived by the patient as If one looks at a bright and brushes or sheaves radiating
a scotoma. The recovery of 1. The patient should diffusely illuminated surface from the point of fixation in
vision is dependent on the wear reading spectacles and with no contrasting features, the form of Maltese cross can
ability of the photoreceptors cover one eye. a series of fast moving, lumi- be seen. The brushes have
to re-synthesize visual pig- nous points or spots can be contrasting yellow and blue
ments. The test is performed 2. The patient is asked to readily seen. The spots tend hues. The darker portions of
as follows: look directly at the center dot to move in a generally the Maltese pattern are yel-
with the uncovered eye and curved pattern, while trail- low, whereas the brighter
1. The best-corrected report any distortion, wavy ing short, tapering segments portions are blue. This phe-
distance visual acuity is de- lines, blurred areas or blank behind them. The spots are nomenon is caused by varia-
termined. spots anywhere on the grid. best seen if the background tions in absorption of plane-
is illuminated by blue light polarized light by oriented
2. The patient fixates the Two Point Discrimination in the spectral region of 350 molecules of xanthophyll
light of a pen torch or an in- Test to 450nm. Since this region pigment in the foveal retina.
direct ophthalmoscope held contains the spectral absorp- If the yellow pigment ar-
about 3 cm away for about The ability to distinguish tion peak of hemoglobin, it rangement in the fovea is dis-
10 seconds. two illuminated points of has been suggested that the rupted by pathology in the
light suggests good retinal moving particles represent inner retinal layers, the
3. Thephotostressrecov- function. Two illuminated red blood cells passing brushes will not be seen.
ery time (PSRT) is measured points of 2 mm diameter size through the retinal capillar-
by the time taken to read any and 2 inches apart are placed ies.5 In a normal subject 15 or Maxwell’s Spot
three letters of the pre-test 2 feet away from the patient’s more of moving corpuscles A subject with a normal
acuity line. eye. The patient is then asked are seen. Abnormal Blue
to indicate whether he can Field Entoptic phenomenon macula will see a 3- degree
4. The test is performed perceive the two points sepa- is constituted by the findings dark ring surrounding fixa-
on the other, presumably rately. of tion upon looking through a
normal eye and the results blue filter at a brightly illu-
are compared. Entoptic Phenomenon (a) failure to see any cor- minated white surfaced.
Entoptic phenomenon is puscles Usually a smaller dark spot
In a patient with macular is seen at the fixation point
lesion the PSRT will be referred to visual percep- (b) partial loss of cor- itself. The dark ring and the
longer (50 seconds or longer) tions that are produced or in- puscles in one part of the spot will fade as the eye
as compared with the normal fluenced by the native struc- field adapts to the blue light.
eye whereas in a patient with tures of one’s own eye. These can be restored by re-
an optic nerve lesion there Illumination of the fundus by (c) visibility of less num- adapting to a yellow light; i.e.
will be no difference. parallel light rays allows vi- ber of corpuscles by having the subject look
sualization of small opacities through a yellow filter for a
The Amsler grid located close to the retina. (d) slow corpuscular moment. Following this, the
The Amsler grid test Since the columns of blood movement blue filter will again elicit the
contained within retinal dark ring and spot.
evaluates the 100 of visual blood vessels are linear Tests dependent on the Some visual physiologists
field surrounding fixation. opacities situated in front of Macular Pigment believe that perception of the
The chart is composed of a the retinal photoreceptors, Maxwell’s Spot depends on
grid of lines containing a cen- this makes retinal blood ves- Two tests are believed to the screening of the photore-
tral black fixation spot. The sels visible. If a focal source depend on the arrangement
squares on the grid are 5 mm of light (such as small pen- of the yellow pigment in the
in size and subtend a visual inner retinal layers of the
angle of 10 at 30 cm viewing macula lutea. These are the
distance.

December, 2003 270 DOS Times - Vol.9, No.6

REVIEW

ceptors by the macular pig- visual defect. By contrast ac- defective into protan , (Pitt’s law). The results are
ment while others believe deutan, tritan (blue blind) diagnostic for the type of
that variations in the relative quired dyschromatopsias axes of confusion. Mild color dyschromatopsia. The color
numbers of different types of defectives score normally. blind subject exhibits char-
color receptors in the foveal are asymmetric, are accom- acteristic spectral regions of
region explain this phenom- 3. AOHRR Plates: The poor hue discrimination
enon. panied by other visual dys- AOHRR plates have colored which differ from the normal
symbols and a gray back- subject since the intrinsic
The Maddox Rod Test functions and most com- ground. The hues of the color saturation for the color de-
The Maddox rod consists symbols occur at the neutral fective differs from the nor-
monly show irregularity in points of color defective pa- mal.
of a series of fused cylindri- tients. The saturation of the
cal red glass rods, which con- color testing not usually seen test symbol colors is progres- Farnsworth-Munsell 100
vert the appearance of a sively increased in succes- Hue test
white spot of light into a red in the congenital variety e.g. sive plates. The colorblind
streak. The optical properties patient has difficulty dis- The subject arranges 85
of rods cause the streak of acquired color defects are the cerning the test symbols colored caps (4 separate
light to be at an angle of 900 from the gray background. boxes each containing about
with the long axis of the rod; blue-yellow dyschromatop- This test is useful for screen- 20 caps) such that each suc-
when the glass rods are held ing and categorization of ceeding cap is closest in hue
horizontally, the streak will sia of central serous red-green and blue-yellow to the preceding cap. The F-
be vertical and vice-versa. defectives in terms of sever- M 100 Hue test is based en-
The rods are placed in front chorioretinopathy and re- ity of the defect and the axis tirely on hue discrimination
of the right eye. This dissoci- of confusion. It cannot differ- and not on color confusion
ates the two eyes because the tinitis pigmentosa, or the pairs as the caps are balanced
red streak seen by the right for saturation and intensity.
eye cannot be fused with the red-green defect of acquired The test rates the degree of
unaltered white spot seen by color discrimination in nor-
the left eye. The amount of cone degeneration or optic mal subjects in addition to
dissociation is measured by measuring zones of poor hue
the superimposition of the neuritis. Tests for color vision discrimination in color
two images using prisms. defectives. Specific zones of
The base of the prism is include color confusion test poor hue discrimination
placed in the position oppo- identify the nature of the dys-
site to the direction of the de- and in the clinical sphere in- chromatopsia.
viation. Both vertical and
horizontal deviations can be clude the Ishihara test plates, Nagel Anomaloscope
measured in this way. This test is based on color
the Farnsworth Penal D-15,
Color Vision matching. It is considered to
The central 30-60 degree the American Optical be the best method for accu-
rate classification of red-
of the visual field processes Hardy-Rand-Rittler pseudo- green defects. The subject
the trichromatic color vision. must match a standard yel-
Hereditary dystrophies of isochromatic plates low light in color and bright-
the posterior pole, non-he- ness with a mixture of red
reditary maculopathies and Nagel Anamoloscope is considered to be and green. Normal subjects
certain optic nerve condi- the best method for accurate give a narrow matching
tions often result in acquired range, the so-called Rayleigh
color defects. classification of red-green defects. match. Characteristic match-
ing patterns are elicited for
As a rule, congenital (AOHRR), and the Sloan entiate a dichromat (a patient the different types of red-
trichromatic color deficien- Achromatopsia Test. with only two cone pigment) green dyschromatopsias and
cies are not particularly rare, from an anomalous trichro- achromats.
affect males, are symmetric, Color Confusion Tests mat (one with three cone pig-
involve red-green color sys- 1. Ishihara Plates: This ments).
tem, and occur as isolated
test is based on color confu- 4. Sloan Achromatopsia
sion in the red-green color- Test: This test presents to the
blind patient. The color of the observer a series of highly
test symbol and the back- saturated colors which he/
ground is of such hue, satu- she is asked to match to a se-
ration and the intensity so as ries of gray shades. The ach-
to be confused by protans romat, or totally colorblind
(red blind) and deutans patient, makes characteristic
(green blind). matches while a dichromat
or trichromat cannot make
2. Farnsworth Panel D-15: any match.
This test is also based on
zones of color confusion. The Hue discrimination test
subject is asked to arrange a Hue (wavelength) dis-
series of 15 colored caps such
that each succeeding cap crimination for the color de-
appears most similar in ap- fective and normal is best at
pearance to the previous cap. spectral zones of intrinsic
The D-15 Panel classifies the desideration and poorest at
moderate and severe color zones of best saturation

December, 2003 271 DOS Times - Vol.9, No.6

REVIEW

Foveal Flicker Sensitivity square wave function. In or- sitivity loss can be seen in lowing the bleach, the pa-
There is a variation of der to explore spatial pro- different patients with the tient fixates on a test light
cessing by the visual system, same Snellen acuity score. located 12-15degrees eccen-
foveal sensitivity to flicker as gratings have been intro- tric to the stimulus light
a function of temporal fre- duced with bar luminance Dark Adaptation which itself can be varied in
quency. A small flickering constantly changing to fol- Dark adaptation refers to diameter. This retinal loca-
test light is superimposed on low a sine wave function. tion is in an area of good
a constant background lumi- Discrete edges are not seen the ability of visual system cone-rod mix. The intensity
nance (fig.1). The luminance in such gratings. both rods and cones to re- of the test light is slowly in-
of the flickering test light is cover sensitivity following creased from below thresh-
sinusoidally modulated; i.e. A grating detection test is exposure to light. Dark ad- old until the patient detects
it increases and decreases in performed by having the pa- aptation is tested by it. The minimal intensity for
a sinusoidal fashion above tient fix on the center of a si- Goldmann – Weekers adap- detection is the threshold at
and below the mean lumi- nusoidal grating, preferably tometer (fig.2). this point in time. By taking
nance resulting in maximum small enough to fall within a threshold reading every
and minimum peak lumi- the macular region. The The eye is exposed to a minute a curve of the chang-
nance. The mean luminance mean luminance of the grat- standard light bleach (pread- ing threshold versus time of
of the test light is equal to that ing is held constant at all aptation for 15 minutes). This dark adaptation is obtained.
of the surround. The test spot times. The pattern is alter- precedes the plotting of the
is usually 0.5 – 2.0 degrees in nated at a regular rate with a dark adaptation curve. Fol-
size for foveal flicker sensi- homogenous screen of the
tivity. same mean luminance. The
patient indicates when he
For each temporal fre- can or cannot see the on – off
quency value (cycles per sec- bar pattern. This test has
ond or Hz), the threshold is been applied to visual prob-
the minimum modulation lems resulting from cerebral
depth at which detection of and retinal pathology.7
flicker occurs. The recipro-
cal of the threshold is the sen- The bar width at the cut-
sitivity. The falloffs in sensi- off frequency correlates
tivity were found at high closely with the component
temporal flicker frequencies width of the smallest Snellen
in certain retinal disorders, letter correctly identified.
even when visual acuity was However, in patients with
normal.6 cerebral lesions involving
the visual pathways and
Grating Psychophysics with the presumed maculo-
Traditionally gratings are pathy of retinitis pigmen-
tosa, the curve is no longer
composed of alternating dis- predictable from the visual
crete dark and light bars. acuity measurement i.e. dif-
These bars have a changing ferent types of contrast sen-
luminance described by a

Highlights for January Issue of DOS Times

Ø Problems in RD Surgery : Dr. C.M. Shroff
Ø Ultrasound Biomicroscopy in Glaucoma : Dr. Tanuj Dada
Ø Phaconit: Current Prespective : Dr. Amar Agarwal
Ø Complication & Management of Contact Lens : Dr. J.S. Saini
Ø Focus on AMRD

December, 2003 272 DOS Times - Vol.9, No.6

REVIEW

The curve is normally Perimetry a generalized pathologic the macula would not be ex-
biphasic with a “rod-cone Perimetry can also test the process and in such cases pe- pected to affect this test.
break” at about 10 minutes. ripheral field may also show
The early part of the curve retinal function. Central or abnormalities. 2. E l e c t r o o c u l o g r a p h y
represents cone adaptation paracentral scotomas are (EOG)
and the later part of the curve elicited in posterior pole dis- Electrophysiological Tests
represents the rod adapta- ease and the plotting of sev- 1. E l e c t r o r e t i n o g r a p h y The EOG measures the
tion. With regard to the eral isopters by variation of (ERG) changes in the corneoretinal
macular area this test can be test object; color, size and in- potential of the eye under
modified so that foveal func- tensity help to better charac- The clinical electroretino- varying conditions of illumi-
tion can be studied. terize field defects. Macular gram is the recording of the nation. To record this , two
disease is sometimes part of electrical potential wave- electrodes are placed on the
form generated by the total skin, one at the lateral can-
(preganglionic) retina in re- thus and the other at the me-
sponse to a diffuse light dial canthus. The subject is
stimulus (fig.3). The test is asked to shift fixation back
performed using a corneal and forth between two red
contact lens electrode which lights that turn on and off
records changes in the sequentially in an alternat-
corneo-retinal potential with ing fashion. The angular dis-
each light stimulus.8 The tance between the lights and
clinical important compo- consequently the eye move-
nents are the initial corneal ment excursion is generally
negative a-wave and the sec- 30 degrees. Since the
ond positive b-wave. The a- corneoretinal potential is
wave is believed to emanate positive with regard to the
from the inner segments of cornea, the EOG recording is
the photoreceptors and the positive when the patient’s
b-wave from Muller cells in cornea (gaze) is turned to-
the bipolar region. The peak ward the canthus with the
amplitudes and latencies as recording electrode. The
well as waveform shape are record is negative when the
considered in the interpreta- eye turns to the opposite di-
tion of the ERG. Since the rection (toward the reference
ERG monitors preganglionic electrode). Several measure-
retinal activity, a patient due ments are taken every
to optic atrophy may have a minute for a total of 15 min-
normal ERG. utes in darkness and then 15
minutes in the light. A plot
ERG is a mass retinal re- of the average amplitude
sponse; an isolated lesion of

December, 2003 273 DOS Times - Vol.9, No.6

REVIEW

value for each minute normal.9 There are, however represents alternating dark 3. Guyton D.L.: Instuments for
against time normally shows several clinical conditions in and light bars in the form of measuring retinal visual acu-
a minimum trough value which this does not hold true a sinusoidal grating. The ity behind cataracts. Ophthal-
during the dark period and which include Best’s light bars become dark and mology 1982; 89(8S): 98-103.
a maximum peak value in the Vitelliform macular dystro- the dark bars become light
light (fig.4). phy, Butterfly dystrophy, with the pattern reversing at 4. Severin S., Harper J., Culver
fundus flavimaculatus and a constant rate. A third tech- J.: Photostress test for the
The dark trough of the generalized drusen. In these nique employs a checker- evaluation of macular func-
standing potential is be- conditions ERG is normal board pattern stimulator tion. Arch. Ophthalmol. Otola-
lieved to depend on the in- but EOG is abnormal. with alternation of dark and ryngol. 1975; 79: 701.
tegrity of the pigment epithe- light checks.
lial outer segment region. 3. Visually Evoked Re- 5. Loebl M. and Riva C.E.: Macu-
The light rise depends on the sponse (VER) The usefulness of the VER lar circulation and the flying
function of the mid-retinal in detecting lesions of the corpuscles phenomenon. Oph-
layers in addition to the outer The visually evoked re- macula must be inferred by thalmology 1978; 85: 911-917.
retina-pigment epithelial sponse is a measure of the the fact that the ultimate
complex. The absolute value electrical potential gener- record reflects neural trans- 6. Tyler C.W.: Flicker frequency
of the corneoretinal potential ated in response to a visual mission along the entire vi- response functions in the di-
is variable, the light peak/ stimulus. It is recorded with sual pathway from retina to agnosis of retinal disorders.
dark trough ratio is found to scalp electrodes placed over occipital lobe. Therefore, ab- Presented at ARVO meeting.
be a reliable parameter of the occipital lobe region, a normality anywhere along Sarasorta Fla. 1976.
retinal function and the nor- cortical area with primarily the system may result in ab-
mal lower range is 170% (cal- a macular representation.10 normal VER. 7. Bodis-Wollner I., Diamond S.:
culated by taking the ratio of There are many different The measurement of spatial
the maximum light adapted techniques of foveal stimu- References contrast sensitivity in cases of
to the minimum dark lation in VER testing. In one blurred vision associated with
adapted response and mul- method diffuse light stimu- 1. Cohen M.M.: Laser interfer- cerebral lesion. Brain 1976;
tiplying it by 100). This ratio lus flashes intermittently. ometry: evaluation of poten- 99:695.
is known as Arden ratio. This method is most useful tial visual acuity in the pres-
in the assessment of sus- ence of cataracts. Ann. Oph- 8. Lawwill T.: The bar pattern
EOG is a reflection of the pected monocular pathol- thalmol 1976; 8: 845-849. electroretinogram for clinical
generalized retinal respon- ogy. In second method retina evaluation of the central
siveness. Therefore, it is ab- is stimulated by a patterned 2. Minkowski J.S. and Guyton retina. Am. J. Ophthalmol. 1974;
normal in most of those con- stimulus. One such pattern D.L.: Potential acuity meter us- 78: 121.
ditions in which ERG is ab- ing a minute aerial pinhole ap-
erture (poster abstract). Oph- 9. Francois J., Verriest G.,
thalmology 1981; 88(9S): 95. deRouck A.: Electrooculogra-
phy as a functional test in
pathological conditions of the
fundus. I. First results. Br. J.
Ophthalmol. 1956; 40: 108.

10. Sokol S.: Visually evoked po-
tentials: theory, techniques
and clinical applications. Surv.
Ophthalmol. 1976; 21; 18.

Congratulations!

Ø Dr. V.K. Malik, Eye Surgeon, Distt. Hospital, Meerut has got the appreciation award
from Govt. of U.P. for doing highest number of I.O.L. Surgeries, year 2002-03.

Ø Dr. Pradeep Sharma, Additional Professor, R.P. Centre has been recently awarded the
following:

w Awarded International Membership of American Association of Pediatric Ophthalmology and
Strabismus.

w Awarded Retina Foundation Medal Oration by the Gujarat Ophthalmological Society, 11th Oc-
tober, 2003.

w Awarded Rustumji Ranji Medal Oration by the Andhra Pradesh State Ophthalmological Soci-
ety, 18th October, 2003.

Ø Dr. Rajiv Mohan, Joint Director & Consultant Mohan Eye Institute, on Being Awarded
FRCS (Ophthalmology) and Invited as Examiner at Glasgow by the Royal College of
Physicians & Surgeons of Glasgow

December, 2003 274 DOS Times - Vol.9, No.6

APPLIANCES

Ocular Ultrasonography aqueous and vitreous con-
duct sound at a velocity of
Atul Kumar MD, Nikhil Pal MD, 1532 m/sec, intraocular and
Sanjeev Nainiwal MD, orbital soft tissue at a veloc-
Raj Vardhan Azad MD, FRCS (Ed) ity of 1550 m/sec, and the
normal lens at 1641 m/sec.
History and accuracy of the equip- of diseases, including pri-
Developed in the late ment and methods have im- mary and secondary tumors As the ultrasound passes
proved (see box). Echogra- of the orbit, inflammatory through tissues, part of the
1950s and early 1960s, diag- phy is indicated whenever diseases, and changes sec- wave may be reflected back
nostic ophthalmic ultra- complete or partial opacifi- ondary to thyroid disease. toward the probe; this re-
sonography remains a criti- cation of the media prevents flected wave is referred to as
cal ancillary test for the clini- an adequate clinical exami- Physics And Instrumenta- an echo. Echoes are pro-
cal evaluation of the opaque nation of either the anterior tion duced by acoustic interfaces
media globe and abnormal or posterior segment. It has that are created at the junc-
orbit.Ultrasound was first also proved to be very use- Ultrasound is an acoustic tion of media with different
used in ocular diagnosis in ful in clear media for the dif- wave that consists of an os- sound velocities.The greater
1956 by Mundt and Hughes, ferentiation and measure- cillation of particles. By defi- the difference in sound ve-
who employed the A-scan ment of intraocular tumors nition, ultrasound waves locity of the media that cre-
technique. Their work was and inflammatory lesions. have a frequency greater ate the acoustic interface, the
refined in the late 1950s and Before beginning any exami- than 20 kHz (i.e., 20,000 os- stronger the echo. For ex-
early 1960s by Oksala and co- nation, the echographer cillations per second), which ample, the lens (velocity =
workers from Finland, who should be informed of the renders them inaudible. For 1641 m/sec) produces a
did extensive work on the diagnostic ophthalmic ultra- stronger echo when adjacent
detection and differentiation to aqueous (velocity = 1532
of various ocular disorders, Echography is indicated whenever m/sec) as opposed to blood
also using the A-scan complete or partial opacification of the (velocity = 1550 m/sec), as
method. At about the same in a hyphema.
time, Baum and Greenwood media prevents an adequate clinical
developed the first two-di- examination of either the anterior or The returning echoes are
mensional B-scan for use in affected by many factors, in-
ophthalmology, using the posterior segment. cluding the size and shape
immersion technique. Fur- of acoustic interfaces, the
ther pioneering work using pertinent history and clini- sound, frequencies used are angle of sound beam inci-
the immersion B-scan met- cal findings. generally in the range 8 to 10 dence, absorption, scatter-
hod was performed by Ed- MHz (1 MHz = 10G cps). The ing, and refraction. An un-
ward Purnel and Jackson Biometry is another im- very high frequencies used derstanding of these prin-
Coleman and co-workers. portant contribution of ultra- in ophthalmology produce ciples is important for the
The first commercially avail- sound in ophthalmology. short wavelengths, in the performance of accurate ul-
able contact B-scanner, in Reliable intraocular lens range of 0.2 mm. These very trasound examinations.
which the handheld probe (IOL) calculations depend on short wavelengths allow suf-
was applied directly to the accurate and precise axial ficient resolution of the Clinical echography de-
closed lid, was introduced by length measurements. Mea- minute structures in the eye pends on technology that
Nathaniel Bronson in 1972. surements of the globe have and orbit. In contrast, ab- emits an ultrasound wave
also become important in dominal and obstetric ultra- and then detects and pro-
Indications for Echography evaluating conditions such sound require frequencies in cesses the returning echoes.
Indications for oph- as congenital glaucoma, mi- the range 1 to 5 MHz, which The basis of the system is the
crophthalmia and nanoph- provide the longer wave- piezo-electric material (e.g.,
thalmic ultrasound (i.e., thalmos, persistent hyper- lengths that are necessary for quartz crystal) that is located
echography) have steadily plasia of primary vitreous deeper penetration of soft near the tip of the transducer
increased as the capabilities (PHPV), phthisis bulbi, and tissue.The speed at which (i.e., probe). (Fig 1) This
myopia. Orbital ultrasonog- ultrasound travels depends transducer emits pulses of
Dr. R.P.Centre for Ophthalmic raphy is most useful in evalu- on the medium through ultrasound waves (i.e., the
Sciences, AIIMS, ation of patients with exoph- which it passes. For example, sound beam) and then re-
New Delhi. thalmos related to a number ceives the returning echoes.
The detected echoes are pro-
cessed in the instrument
(e.g., filtered and amplified)

December, 2003 275 DOS Times - Vol.9, No.6

APPLIANCES

and are then displayed on the OPAQUE OCULAR MEDIA -(70-80db)
screen as echograms. This Anterior segment l Select lowest gain com-
signal processing differs Ø Corneal opacification patible with clear image
from one instrument to an- Ø Anterior chamber hyphema or hypopyon Types of B-Scan (Globe)
other and is critical in deter- Ø Miosis or pupillary membrane q Fundamental (Fig 4a)
mining the character of the Ø Cataract l Axial(Fig 4b)
echogram. The ultrasound l Longitudinal(Fig 4c)
instruments used most com- Posterior segment l Transverse(Fig 4d)
monly in ophthalmology are Ø Vitreous hemorrhage or inflammation q Special
the A-scan and the B-scan. l Topographic
CLEAR OCULAR MEDIA l Kinetic
A-scan Anterior segment l Quantitative
A-scan is a one-dimen- Ø Iris lesions
Ø Ciliary body lesions Special examination technique
sional acoustic display in q Topographic echography
which echoes are repre- Posterior segment q Quantitative echography
sented as vertical spikes from Ø Tumors and masses: detection and differentiation q Kinetic echography
a baseline. Spacing of the Ø Retinal detachment: rhegmatogenous vs. exudative
spikes depends on the time Ø Intraocular foreign bodies: detection and localization Examination Techniques
it takes for the sound beam Ø Optic disc abnormalities Specific examination
to reach a given interface and
for its echo to return to the FOLLOW-UP STUDIES techniques have been care-
probe. The time between any BIOMETRY fully designed to allow thor-
two echo spikes can then be Ø Axial eye length ough evaluation of the ante-
converted into distance by Ø Anterior chamber depth rior and posterior segments
knowing the sound velocity Ø Lens thickness of the globe. The type of ex-
of the media from which the Ø Tumor measurement amination performed is de-
echoes are received. The termined by the indication
height of the displayed Indication of orbital USG for examination. The contact
spikes indicates the strength Ø Orbital pseudo tumour method (i.e., the probe is
(i.e., amplitude) of the ech- Ø Orbital lymphoma applied directly to the globe)
oes (Fig. 2). Ø Cavernous hemangioma is used to evaluate the poste-
Ø Orbital lymphangioma rior segment. In those cases
B-scan Ø Orbital abscess in which the anterior seg-
B-scan differs from A- Ø EOM evaluation ment also needs evaluation,
Ø Thyroid ophthalmopathy Vs Myositis an easy immersion technique
scan in that it produces a two- Ø Optic nerve evaluation-Optic disc coloboma has been developed that uti-
dimensional acoustic section lizes the same contact instru-
(such as a photograph) by coalescence of multiple dots l Avoid scanning through ment
using both the vertical and on the screen forms a two- lens
horizontal dimensions of the dimensional representation Basic screening and spe-
screen to indicate configura- of the examined tissue sec- Examination technique cial examination techniques
tion and location. A section tion (Fig. 3). l Brief clinical history for lesion differentiation (to-
of tissue is examined by an l Set the instrument(Globe- pographic, quantitative, and
oscillating transducer that How to get best image 1,Orbit-5) kinetic echography) have
emits a sound beam that l Beam must fall perpen- l Supine/recline position been developed for the
“slices” through a tissue, dicular to the area of interest l Close the eye lid evaluation of posterior seg-
much like a slice with a knife. l Lesion must be centered l Apply methyl cellulose ment disorders.
Ophthalmic B-scan instru- to the beam path l Give fixation target
ments require a focused l Select lowest gain com- l Probe in desired direction Positioning the patient
beam that functions at a fre- patible with clear image & position If separate A-scan and
quency in the range of 10 l Place the probe through l Begin the examination
MHz. An echo is represented open eye lid (preferable) l Start with med – high gain contact B-scan instruments
as a dot on the screen rather are used, they may be placed
than as a spike. The strength on one large or two small
of the echo is depicted by the carts. The patient is seated in
brightness of the dot. The a reclining examining chair
of adjustable height. While

December, 2003 276 DOS Times - Vol.9, No.6

APPLIANCES

most examinations are per- on the left side of the In the axial scan, the
formed with the patient re-
clined, it is occasionally help- echogram. The fundus, patient fixates in pri-
ful to have the patient in a
sitting position. located on the side of mary gaze and the

The basic screening ex- the globe opposite the probe is placed on the
amination is performed to
detect lesions of the posterior probe, is represented center of the cornea,
segment. It is best to use both
A-scan and B-scan for lesion on the right side of the thus displaying lens
detection, but it is suggested
that the novice begin with A- echogram. The upper and optic nerve in the
scan; this is to allow the new
echographer to master the A- part of the echogram center of the echogram.
scan examination techniques
in the normal eye, a prereq- corresponds to the por- The axial scan does not
uisite to using the standard-
ized A-scan for the more dif- tion of the globe where yield as much informa-
ficult differentiation of le-
sions. Furthermore, the the probe marker is di- Fig.1: Parts of ultrasonography machine tion and thus is per-
small, pencil-like A-scan rected. The center of formed at the end of the
probe allows thorough
screening of the peripheral the screen corresponds topographic examina-
fundus, including the ciliary
body. to the central portion of tion.

Special examination tech- the probe face. Since
niques
Topographic echography— this provides the best Transverse scans
shape, location, and exten-
sion resolution, a lesion With transverse scans,

As soon as a lesion is de- should always be cen- the probe is placed on
tected, topographic echogra-
phy is performed to deter- tered within the the globe with the long-
mine location, general clas-
sification, and specific con- echogram. est diameter of the oval
figuration. B-scan is ideally
suited for the initial topo- In practice, the probe face positioned
graphic evaluation since the
moving, focused sound echographer applies parallel (i.e., tangen-
beam provides a two-dimen-
sional display. It is also im- methylcellulose to the Fig.2. Normal standardized A-scan tial) to the limbus. In
portant, however, to appre- probe face as a cou- echograms. I, Initial spike corresponding this way, the back-and-
ciate a lesion’s topography pling medium. The B- to probe tip (corneal spike hidden by ini- forth movement of the
with the A-scan in order to scan probe is then tial spike); A, anterior lens; P, posterior transducer also occurs
carry out subsequent special placed directly on the lens; M, multiple signal; V, echo-free vitre- parallel to the limbus.
examination techniques (i.e.,
quantitative and kinetic). It globe (i.e., conjunctiva ous cavity; R, retina; S, sclera; O, orbital The sound beam then
is essential that scanning
techniques be systematically or cornea). Examina- soft tissue. oscillates back and
performed with both B-scan
and A-scan if reliable results tion through the lids is forth across the oppo-
are to be achieved
generally avoided be- site fundus, producing
The probe face is always
represented by the initial line cause of sound attenu- a circumferential slice.

ation by the lids. In ad- This orientation is ap-

dition, with the lids propriate for showing

closed, the the lateral extent of a le-

echographer can never sion (e.g., extending

be certain which por- from 2- to 4-o’clock me-

tion of the globe is be- ridians, from 7- to 9:30-

ing evaluated. The par- meridians, etc.)

ticular section of ocu- The designation of the

lar tissue displayed on Fig.3: Normal standardized B-scan transverse scan is de-
the screen depends on echograms termined by the merid-
how the probe is posi- ian that lies in the

tioned and how the middle of the scanning

marker is directed. The three cornea. Thus the sound beam section. For example, if the

basic probe orientations that bypasses the lens, allowing probe is held horizontally

are used to evaluate in- better sound penetration. with its face centered on the

traocular lesions are trans- These scans are performed 6-o’clock meridian, the

verse, longitudinal, and with the patient’s gaze di- middle of the echogram (on

axial. rected away from the probe, the right) will display the 12-

The transverse and longi- toward the meridian being o’clock meridian of the fun-

tudinal scans are used most examined. This allows a dus; this probe position is

commonly because the wide surface of globe on called a transverse scan of the

probe is placed on the con- which to place and shift the 12-o’clock meridian. If the

junctiva peripheral to the probe. probe is placed in a vertical

December, 2003 277 DOS Times - Vol.9, No.6

APPLIANCES

Fig.4a: Schematic diagram of Fig.4b: Axial scan Fig.4c: Longitudanal scan Fig.4d: Transverse scan
fundamental USG scan (H:
Horizontal scan V: Vertical
scan O: Oblique scan)

orientation at the 3-o’clock parallel) to the limbus. The is being examined. For ex- Axial scans
limbus, the sound beam sound beam sweeps along ample, if the probe is placed The axial orientation is the
sweeps across the 9-o’clock the meridian opposite the on the 6-o’clock meridian,
meridian; this is called a probe rather than across the the sound beam sweeps third probe position. This is
transverse scan of the 9- meridian as does the trans- along the 12-o’clock merid- performed with the probe
o’clock meridian. verse scan. In this way, the ian; this is designated as a face centered on the cornea;
longitudinal scan shows the longitudinal scan of the 12- the sound beam is directed
By convention, horizontal anteroposterior extent of a le- o’clock meridian (Fig 4c). through the center of the lens
transverse scans (i.e., trans- sion rather than the lateral The use of the longitudinal and the optic nerve . As men-
verse scans of the 12- or 6- extent Another way to think probe orientation greatly fa- tioned previously, this scan
o’clock meridians) are per- of this orientation is as a ra- cilitates three-dimensional is the easiest for
formed with the marker ori- dial section (like the spoke thinking and promotes a bet- echographers to understand
ented toward the nose. of a wheel) with the sound ter understanding of B-scan because it displays the lens
Therefore the upper part of and optic nerve in the center
the echogram always repre- B-scan differs from A-scan in that it of the echogram, thus sim-
sents the nasal portion of the produces a two-dimensional acoustic plifying orientation of the
globe. On the other hand, section (such as a photograph) by using pathologic condition. Unfor-
vertical transverse scans (i.e., both the vertical and horizontal dimen- tunately, however, sound
3- or 9-o’clock meridians) are sions of the screen to indicate configura- attenuation and refraction
performed with the marker from the lens often hinder
directed superiorly, so the tion and location. resolution of the posterior
top of the echogram repre- portion of the globe, thus lim-
sents the upper portion of the beam sweeping from the findings. It is often the opti- iting the usefulness of this
globe. Oblique transverse optic disc out toward the mal method of displaying scan (Fig. 4b). It is helpful,
scans (transverse scans of the periphery along a given me- the posterior and peripheral though, for documenting le-
1:30, 4:30, 7:30, or 10:30-me- ridian. In longitudinal scans, insertion of a membrane, as sions and membranes in re-
ridians) are performed with the marker is always di- well as the posterior and an- lation to the optic nerve and
the marker directed toward rected toward the center of terior borders of tumors. This is also useful for evaluating
the upper portion of the the cornea, regardless of technique is especially help- the macular region.
globe. which meridian is being ex- ful for evaluating those
amined. This produces an membranes that insert into Topographic B-scanning
Longitudinal scans echogram with the optic disc the optic disc at steep angles If a lesion is detected with
Longitudinal scans are and posterior fundus dis- or when an anterior structure
played on the lower portion (e.g., lens or lens implant) either the A- or B-scan basic
also performed with the of the screen, whereas the pe- produces strong sound at- screening examination, to-
probe placed peripheral to ripheral globe is displayed tenuation (precluding opti- pographic evaluation of the
the limbus. The probe is ro- superiorly. The designation mal visualization with an lesion is then performed. The
tated 90 degrees from the of the longitudinal scan is axial scan). lesion is first assessed with
position of the transverse simply that meridian which the appropriate transverse
scan so that the longest di- approach. For example, if a
ameter of the oval probe face lesion is detected in the su-
is perpendicular (rather than perior temporal quadrant of

December, 2003 278 DOS Times - Vol.9, No.6

APPLIANCES

the right eye, a transverse apart). These various A-scan indicates mobility as deter- terior segment structures
scan of the 10:30 meridian is maneuvers help to classify mined by motion of the le- and lesions in ciliary body re-
performed (the probe is the general type of lesion sion echoes following cessa- gion. UBM provides much
placed at 4:30 and the marker (pointlike, bandlike, mem- tion of eye movement. For higher resolution of 25-50mi-
is oriented superonasally). branelike, and masslike) and example, a nonsolid lesion crons than does conventional
The probe is then shifted to evaluate exact location (e.g., PVD or RD) displays B-scan ultrasonography (150
from limbus to fornix, thus and extent. aftermovement, whereas a microns). The clinical appli-
sweeping the sound beam solid lesion (e.g., tumor) does cations of UBM are in
through the lesion from pos- Quantitative echography— not. Vascularity, spontane- glaucoma(open versus
terior to anterior. This allows type I ous motion of echoes on the closed angle closure glau-
display of the lesion’s gross screen, is indicative of blood coma, plateau iris syn-
shape and dimensions, as Quantitative echography flow within vessels. drome), iridocorneal scars,
well as lateral extent (i.e., type I is used to estimate the IOL status, post-trauma and
which meridians are affected reflectivity (i.e., spike height) Anterior segment evalua- can be used to study pars
by the lesion). The longitu- of all detected lesions. Once tion: immersion technique plana sclerotomy ports.
dinal approach is then ap- the sound beam is directed
plied, with the sound beam perpendicular to a lesion, the Indications for anterior Role of Optical Coherence
oriented radially, perpen- amplitude (i.e., height) of its segment evaluation are lim- Tomography
dicular to the transverse spike is observed in the ited because this area is opti-
view. For a lesion located at echogram. This simple tech- cally visible in the vast ma- Optical Coherence To-
the 10:30 position in the right nique is of great value in dif- jority of cases. However, mography (OCT) is a new
eye, the probe face is placed ferentiating many types of when echographic data are imaging modality the prin-
on the 4:30 meridian with the intraocular lesions, such as needed, they may be reliably ciples of which are similar to
marker directed toward the dense posterior vitreous de- obtained with a simple im- B-mode ultrasound, that
center of the cornea. The tachment (PVD) from retinal mersion technique. This is produces high resolution
lesion’s anteroposterior ex- detachment (RD), and mela- accomplished by inserting a (upto 10 microns) cross sec-
tent (between the optic disc noma from other intraocular small scleral shell between tional images of the retina
and ora along the 10:30 me- tumors. The determination the lids. The shell is then .However, OCT utilizes the
ridian) is assessed, and its of reflectivity is necessary for filled with methylcellulose. reflection of a superlumi-
shape and gross dimensions evaluation of a mass lesion’s Using this standoff tech- nescent diode source of light
are reevaluated. internal structure and sound nique, the cornea, anterior with a wavelength of 830nm
attenuation. chamber, iris, lens, and ret- rather than sound waves
Topographic A-scanning rolental (or retroiridal) space from different structures of
Once the involved merid- Quantitative echography— can be evaluated along the the eye and has applications
type II ocular axis with B- and A- in macular hole, macular
ians have been generally scan Immersion axial length edema and ARMD.
determined with B-scan, A- This technique is used measurements can also be
scan is also applied. Lesion solely to differentiate RD obtained with A-scan. More Suggested Reading
topography is always evalu- from dense vitreous mem- peripherally located, ante-
ated at the tissue sensitivity branes. If a membrane like rior structures (i.e., iris, an- 1. Mundt GH, Hughes WF: Ultra-
setting. The probe is first lesion produces a 100% tall terior chamber angle, or cili- sonics in ocular diagnosis. Am J
placed at the limbus of the spike at tissue sensitivity ary body) can also be as- Ophthalmol 41:488, 1956
meridian opposite the les- during quantitative type I sessed by shifting the shell 2. Purnell EW: Intensity modu-
ion’s center. It is then shifted and its other acoustic char- and probe laterally over the lated (B-scan) ultrasonography. In
between limbus and fornix acteristics are equivocal, area to be displayed. Goldberg RE, Sarin LK (eds), Ultra-
to assess the lesion antero- quantitative type II may be sonics in Ophthalmology: Diagnostic
posteriorly (i.e., radially). applied. Recently, Pavlin and col- and Therapeutic Applications, pp 102-
The probe is then shifted leagues have developed a 123. Philadelphia, Saunders, 1967
from side to side (parallel to Kinetic echography new B-scan method for 3. Dallow RL (ed): Ophthalmic
the limbus) to evaluate the Kinetic echography is evaluating the anterior seg- ultrasonography: Comparative
lesion laterally. Another ment. This new technique techniques. Int Ophthalmol Clin 19:4,
helpful technique is to exam- used to dynamically assess utilizes frequencies in the 1979
ine the lesion from different the motion of or within a range of 50 to 100 MHz and 4. Ossoinig KC: Quantitative
sound beam directions (i.e., lesion.Two types of motion is referred to as Ultrasound echography-the basis of tissue dif-
with the probe placed in po- (i.e., aftermovement and vas- Biomicroscopy (UBM). The ferentiation. J Clin Ultrasound 2:33,
sitions that are 90 degrees cularity) can be detected method provides very high 1974
with the appropriate instru- resolution for examining an- 5. Coleman DJ: Reliability of ocu-
mentation. Aftermovement lar and orbital diagnosis with B-
scan ultrasound. Am J Ophthalmol
74:708, 1972

December, 2003 279 DOS Times - Vol.9, No.6

DOS QUIZ NO. 6

DOS QUIZ NO. 6

1. Most common lesion involving anterior segment of eye in AIDS..................................................................
2. Most common symptomatic metastatic uveal tumors ....................................................................................
3. Dilator pupillae orginates from which embryonal layer ................................................................................
4. Most common cause of bull’s eye maculopathy ..............................................................................................
5. Cherry red spot disappears after injury by.......................................................................................................
6. Economic blindness is called when snellen acuity falls below ....................................................................
7. Epithelium of canaliculus is lined by ................................................................................................................
8. Which laser is used in IOL master .....................................................................................................................
9. Magnification caused by direct ophthalmoscope ............................................................................................
10. Most common systemic disease associated with necrotizing scleritis .........................................................

Rules:
l Please send your entries to the DOS office latest by 25th December, 2003.
l Prize Rs. 500/- Courtesy: Syntho Pharmaceuticals
l Quiz Trophy will be given to the member who answers maximum number of quizes in a

year during the Annual GBM of DOS.

Answers for the DOS Quiz No. 4

1. Most common lid tumour in India Sebaceous Cell Carcinoma
2. Epidemic keratoconjuctivitis is caused by Adenovirus 8, 19
3. Stocker line is seen in Pterygium
4. Which Corneal dystrophy is having systemic association Lattice II dystrophy
5. Foldable IOL was invented by Tom Mozzoco
6. Inverse glaucoma is seen in Sphero Phakia
7. "Headlight in the Fog" appearance of fundus is seen in Toxoplasmosis
8. Harada – Ito procedure is indicated in Pure Exclylotropia in Superior oblique palsy
9. Pulfrich Phenomonen is seen in Optic Neuropathy
10. Which acid & alkaji injury is most dangerous NH3OH & HF

December, 2003 280 DOS Times - Vol.9, No.6

JOURNAL ABSTRACTS

Comparison of scleral buckling with perfluoropropane gas injection. Four eyes had radial neuroto-
combined scleral buckling and pars mies performed. The patients were examined by fundus pho-
plana vitrectomy in the management of tography, fundus fluorescein angiography, optical coherence
rhegmatogenous retinal detachment with tomography, and Goldmann visual field analysis.
unseen retinal breaks No patients suffered from neovascular glaucoma. Visual re-
covery was seen in patients with and without neurotomy but
Tewari HK, Kedar S, Kumar A, Garg SP, Verma LK. some patients had cataract extraction to allow visualisation
for PPV. Fundus photography demonstrated reduced engorge-
Clin Experiment Ophthalmol. 2003 Oct; 31(5): 403-7. ment of retinal veins in two of the patients with neurotomy
Dr Rajendra Prasad Center for Ophthalmic Sciences, AIIMS, and one with PPV alone. Optical coherence tomography dem-
New Delhi, India. onstrated macular oedema in three patients with neurotomy
and all patients with PPV alone. Segmental visual field loss
Authors compared conventional scleral buckling and com- was seen in one patient with neurotomy suggesting damage
bined pars plana vitrectomy and scleral buckling procedures to the optic nerve head.
in rhegmatogenous retinal detachments with unseen retinal
breaks. Forty-four consecutive eyes with uncomplicated, pri- PPV is safe in ischaemic CRVO. Combined with mild PRP
mary rhegmatogenous retinal detachments with a clear me- and intraocular gas injection the risk of neovascular glaucoma
dia and unseen retinal breaks were randomized to two groups. is low. Neurotomy can be added to try to improve the chances
The scleral buckling group underwent 360 degrees scleral of recovery of central vision but may cause additional periph-
buckling, cryopexy and external subretinal fluid drainage. In eral visual field loss.
the combined surgery group, 360 degrees scleral buckling, pars
plana vitrectomy, air-fluid exchange, endolaser and injection Therapeutic contact lenses: the role of
of 14% perfluoropropane gas was done. Results showed at 3
months follow up the primary reattachment rate was 80% (16/ high-Dk lenses.
20 cases) in the combined surgery group, and 70% (14/20 cases)
in the scleral buckling group (P = 0.716). The visual acuity Foulks GN, Harvey T, Raj CV.
improved significantly from a preoperative median of hand Ophthalmol Clin North Am. 2003 Sep;16(3):455-61.
movement (HM; range: HM to 6/60; similar in both the Department of Ophthalmology, University of Pittsburgh School
groups), to a median of 6/60 (range: perception of light to 6/ of Medicine
18) in the combined surgery group and a median of 6/36
(range: HM to 6/18) in the scleral buckling group, the differ- Currently, the armamentarium of contact lenses that can
ence between the two groups not being statistically signifi- be used for therapeutic effect provides a wider selection of
cant (P = 0.4). The number of intraoperative and postopera- lenses than ever before. If the therapeutic goal is protection
tive complications was more in the combined surgery group. and healing of the corneal epithelium, epithelial or stromal
(Four cases were lost to follow up and were doing well when edema is best avoided, and the selection of a high-Dk silicone
last examined.) They conclude the conventional scleral buck- hydrogel (balafilcon A, lotrafilcon A) lens or a very thin mem-
ling was found to be a safe and effective technique in the pri- brane-type lens (crofilcon) is the best choice. If the goal is sur-
mary management of uncomplicated, rhegmatogenous reti- face protection as well as stimulation of stromal wound vas-
nal detachments with unseen retinal breaks when the media cularization, selection of a low-water content, thick, hydro-
is clear. philic lens is the better option. If the patient is prone to lens
loss or requires frequent replacement of the therapeutic lens,
Pars plana vitrectomy, intraocular gas, a prudent economic decision is to select a daily disposable
moderate-water content lens. Specific circumstances may man-
and radial neurotomy in ischaemic cen- date the selection of a specific therapeutic lens. Patients with a
prior history of active giant papillary conjunctivitis may be
tral retinal vein occlusion better served by the use of a crofilcon glyceryl methacrylate
lens, which has a lower incidence of this complication. Patients
TH Williamson, W Poon, L Whitefield, N Strothoudis and who have dry eye may benefit from a higher-water content
P Jaycock lens if adequate unpreserved tear supplementation is provided
British Journal of Ophthalmology 2003;87:1126-1129 with or without punctal occlusion. The options when select-
Department of Ophthalmology, St Thomas’s Hospital, London ing a therapeutic contact lens are wider than ever before. Al-
SE1 7EH, and Department of Ophthalmology, Queen Mary’s though the new generation of high-Dk lenses promises fewer
Hospital, Sidcup, Kent, UK limiting problems of vascularization and infection, one can
use the older traditional therapeutic lenses when induced vas-
In this study pars plana vitrectomy (PPV), mild panretinal cularization of the cornea is needed or when an economic ne-
photocoagulation, and intraocular gas injection were employed cessity exists. Not all of the available lenses are FDA approved
to prevent NVG. The potential role of incision of the lamina for therapeutic use, and such wear is an off-label use. The pa-
cribrosa (radial neurotomy) for visual recovery was examined. tient should be informed of the goal of therapy as well as the
benefits and risks of therapeutic contact lenses.
Eight eyes of seven patients with ischaemic CRVO hadPPV,
mild panretinal photocoagulation, and intraocular

December, 2003 281 DOS Times - Vol.9, No.6

EVENTS

Forthcoming Events – NATIONAL

———————————————————————————————————————————————————

Event Conference Date Venue Contact Person and Address

———————————————————————————————————————————————————

7th Annual Conference of 13th-14th Akal Eye Hospital & LASIK Contact Person: Dr. Balbir Singh Bhaura (M.S.)

Punjab Opthalmological Society Dec. 2003 Laser Centre, Akal Eye Hospital & Lasik Laser Centre,

Jalandhar Model Town, Jalandhar - 144 003

Telefax: 0181-2273606, 2271606, 2461606, 5073604

E-mail: [email protected]

Conference E-mail: [email protected]

62nd All India 8-11 Banaras Hindu Conference Secretariat: Prof. V. Thakur
Ophthalmological Conference Jan. 2004 University, Varanasi Nataraj Eye & Laser Centre, 156B, Ravindrapuri,
Varanasi - 221 005, India
Phone: 0542-2276505, 09415201167
Fax: 0542-2276707
Email: [email protected]

XI International Congress of 23-27th L.V. Prasad Eye Contact Person: Dr. Santosh G. Honavar,
Ocular Oncology Jan. 2004 Institute, Hyderabad ICOO Secretariat, LV Prasad Eye Institute,
LV Prasad Marg, Banjara Hills, Hyderabad
Tel.:+91-40-23548267, e-mail: [email protected]

12th Annual Meeting Vitreo 20-22nd Corbett Claridges Contact Person: Mr. Shobhit Chawla,
Retinal Society of India Feb. 2004 Hideaway, Ramnagar Organising Secretary, Prakash Netra Kendra,
Uttaranchal NH 2, Vipul Khand-4, Gomtinagar,
Lucknow (U.P.)

Annual DOS 3rd-4th India Habitat Centre Contact Person: Dr. Jeewan S. Titiyal,
Conference Secretariat (DOS) R.No. 476, 4th Floor,
April 2004 Lodhi Road, New Delhi Dr. R.P. Centre for Opthalmic Sciences,
New Delhi - 110 029 Ph.: 26589549,
Fax : 26588919, E-mail: [email protected]
Website: http://www.dosonline.org

INTERNATIONAL

Event Conference Date Venue Contact Person and Address

———————————————————————————————————————————————————

Euro Asian Opthalmology Congress 11-15 Shanghai, China Contact: Euro Asian Congress Secretariat
Dec. 2003 Barcelona Tel.: 86-2163-031-757, Fax: 86-2163-029-643
E-mail: [email protected]
8th ESCRS Winter Refractive 23-25 Contact: ESCRS Temple House, Temple Road,
Surgery Meeting Jan. 2004 Blackrock, Co Dublin, Ireland.
Tel.: 3531-209-1100 Fax: 3531-209-1112
International Symposium on 11-14 MONTE CARLO E-mail: [email protected]
Ocular Pharmacology and Mar. 2004 Contact: Iliana Eliar, Assistant Project Manager,
Kenes International Global Congress Organizers
ASCRS Annual Symposium 1-5 SAN DIEGO, CA USA & Association Management Services
XXII Congress of the ESCRS May 2004 PARIS, FRANCE E-mail: <[email protected]>
18-22 Contact: ASCRS Tel.: 1703-591-2220
Sept. 2004 Fax: 1703 591 0614, Web: www.ascrs.org
Temple House, Temple Road, Blackrock,
Co Dublin, Ireland
Tel.: 3531-209-1100 Fax: 3531-209-1112
E-mail: [email protected]

December, 2003 282 DOS Times - Vol.9, No.6

DELHI OPHTHALMOLOGICAL SOCIETY Stamp Size
2 Colour
(LIFE MEMBERSHIP FORM)
Photograph

Name (In Block Letters) _________________________________________________________________________
S/D/W/o _____________________________________________________________ Date of Birth _____________
Qualifications _________________________________________________________ Registration No. __________
Sub Speciality (if any) ___________________________________________________________________________
ADDRESS

Clinic/Hospital/Practice ______________________________________________________________________
_______________________________________________________________ Phone _________________
Residence ________________________________________________________________________________
_______________________________________________________________ Phone _________________
Correspondence ___________________________________________________________________________
_______________________________________________________________ Phone _________________
Email ___________________________________________________________ Fax No. ________________
Proposed by
Dr. _______________________________ Member Ship No. ______________ Signature _________________
Seconded by
Dr. ________________________________ Membership No. ______________ Signature _________________

[Must submit a photocopy of the MBBS/MD/DO Certificate for our records.]

I agree to become a life member of the Delhi Ophthalmological Society and shall abide by the Rules and Regula-
tions of the Society.
(Please Note : Life membership fee Rs. 3100/- payable by DD for outstation members. Local Cheques acceptable,
payable to Delhi Ophthalmological Society)
Please find enclosed Rs.____________in words ______________________________________________________ by
Cheque/DD No.______________________ Dated____________ Drawn on_____________________________________

Three specimen signatures for I.D. Card. Signature of Applicant
with Date

FOR OFFICIAL USE ONLY

Dr._______________________________________________________________has been admitted as Life Member of
the Delhi Ophthalmological Society by the General Body in their meeting held on________________________________
His/her membership No. is _______________. Fee received by Cheque/DD No._______________ dated__________
drawn on __________________________________________________________________.

(Secretary DOS)

December, 2003 283 DOS Times - Vol.9, No.6

INSTRUCTIONS

1. The Society reserves all rights to accepts or reject the application.
2. No reasons shall be given for any application rejected by the Society.
3. No application for membership will be accepted unless it is complete in all respects and accompanied by a Demand Draft of Rs. 3100/- in

favour of “Delhi Ophthalmological Society” payable at New Delhi.
4. Every new member is entitled to received Society’s Bulletin (DOS Times) and Annual proceedings of the Society free.
5. Every new member will initially be admitted provisionally and shall be deemed to have become a full member only after formal ratification

by the General Body and issue of Ratification order by the Society. Only then he or she will be eligible to vote, or apply for any Fellowship
propose or contest for any election of the Society.
6. Application for the membership along with the Bank Draft for the membership fee should be addressed to Dr. Jeewan S. Titiyal, Secretary,
Delhi Ophthalmological Society, R.No. 476, 4th Floor, Dr. R.P. Centre for Ophthalmic Sciences, AIIMS, Ansari Nagar, New Delhi – 110029.
7. Licence Size Coloured Photograph is to be pasted on the form in the space provided and two Stamp/ Licences Size Coloured photographs
are required to be sent along with this form for issue of Laminated Photo Identity Card (to be issued only after the Membership ratification).

DOS Credit Rating System Report Card

DCRS July 2003 – Army Hospital (R&R)

Total No. of Delegates ....................................................................................................................................................................... 121
Delegates from Out side (N) ............................................................................................................................................................. 114
Delegates from Army Hospital (n) ........................................................................................................................................................7
Overall assessment by outside delegates (M) ............................................................................................................................ 888.5
Assessment of case presentation-I (Dr. Lt. Col.A. Banarji) by outside delegates .................................................................... 803.5
Assessment of case presentation-II (Dr. Lt. Col. (Mrs.) Madhu Bhaduria) by outside delegates ............................................ 814.5
Assessment of clinical talk (Dr. D.P. Vats) by outside delegates ................................................................................................ 862.5

DCRS 30th August, 2003 – Sir Ganga Ram Hospital

Total No. of Delegates ................................................................................................................................................................. 82
Delegates from Out side (N) ....................................................................................................................................................... 66
Delegates from Sir Ganga Ram Hospital (n) ............................................................................................................................... 16
Overall assessment by outside delegates (M) ...................................................................................................................... 468.5
Assessment of case presentation-I (Dr. Jasmita Popli) by outside delegates ..................................................................... 440.5
Assessment of case presentation-II (Dr. Anita Sethi) by outside delegates ........................................................................ 476.5
Assessment of Clinical Talk (Dr. S.N. Jha) by outside delegates .................................................................................... …..450.0

DCRS 27th September, 2003 – Hindu Rao Hospital

Total No. of Delegates ................................................................................................................................................................. 70
Delegates from Out side (N) ....................................................................................................................................................... 59
Delegates from Hindu Rao Hospital (n) ...................................................................................................................................... 11
Overall assessment by outside delegates (M) ......................................................................................................................... 432
Assessment of Case Presentation-I (Dr. Ruchi Goel) by outside delegates ............................................................................ 414
Assessment of Case Presentation-II (Dr. A.K. Nagpaul) by outside delegates ................................................................... 401.5
Assessment of Clinical Talk (Dr. Ruchi Goel) by outside delegates .................................................................................... ..433.5

DCRS 1st November, 2003 – Dr. R.P. Centre for Ophthalmic Sciences

Total No. of Delegates ................................................................................................................................................................. 86
Delegates from Out side (N) ....................................................................................................................................................... 62
Delegates from Dr. R.P. Centre for Ophthalmic Sciences (n) ..................................................................................................... 24
Overall assessment by outside delegates (M) ......................................................................................................................... 473
Assessment of Case Presentation-I (Dr. Sachin Kedar) by outside delegates ....................................................................... 447
Assessment of Case Presentation-II (Dr. Murlidhar R.) by outside delegates ..................................................................... 455.5
Assessment of Clinical Talk (Prof. S. Ghose) by outside delegates .................................................................................... ..460.5

December, 2003 284 DOS Times - Vol.9, No.6

TEAR SHEET NO. 6

Newer Diagnostic Modalities in Ophthalmology

Cornea l Advantages: very quick test (45 sec to 6 min), portable instrumenta-
Confocal microscope: scanning slit corneal confocal microscope tion, no spectacle correction required upto 7D of refractive error.
Frame size: 300X200microns with 5 microns thickness.
Uses: For detailed assessment of l Use: for screening
1. Endothelium – l Drawbacks: lack of any longitudinal data, early progression and fo-

¡ high quality specular microscope cal defects may be missed
¡ endothelial count
¡ guttate, endothelial polymegathism and pleomorphism Heidelberg retinal tomography (HRT)
2. Stroma l Confocal Laser Scanning ophthalmoscope (CSLO).
¡ anterior stroma keratocytes morphology l Gives three-dimensional images retina and optic nerve head.
¡ nerve fibres especially after LASIK l Uses a diode laser (670 nm), resolution 30 µ, field of view 10° × 10°,
¡ Flap interface morphology after LASIK.
3. Epithelium and bowman’s membrane 15° × 15°, or 20° × 20°. Pupil dilation is not necessary.
l A three-dimensional image is acquired as 32 consecutive and equi-
Lens:
IOL masters distant optical section images, consisting of 256 × 256 picture ele-
¡ Non-contact optical device based on partial coherence interferom- ments.
l Uses Moorefield regression analysis to classify various disc sectors
eter as normal borderline or abnormal.
¡ Measures the AL from the corneal vertex to the retinal pigment epi- l Use for early diagnosis, detection of early progression and follow-up
of glaucoma.
thelium
¡ Accurate to within ±0.02 mm or better. GDx VCC (Retinal nerve fibre layer analyzer with variable corneal
¡ Five times higher accuracy in measuring AL as compared to USG. compensation)
¡ Measures: AL, Km, Anterior chamber depth, white-to-white corneal l NFA-GDx works on the principle of scanning laser polarimetry.
l Measures retardation of polarized light by RNFL
diameter. l GDx-VCC has a variable corneal compensator that compensates for
¡ Based on Haigis formula
¡ Provides IOL power according to desired IOL type, desired post-op- corneal birefringence, giving more accurate thickness of RNFL.

erative refraction RETINA & Posterior Segment
Draw back: cannot be used in dense cataract and opaque media. HRA (Heidelberg Retinal Angiograph)
¡ Scanning laser tomography
Anterior Segment ¡ Uses argon (488 nm) laser for the fluorescein angiogram and a diode
Ultrasound biomicroscopy (UBM)
l High resolution ultrasound (50MHz ) (788 nm) laser for the ICG angiography.
l Resolution 25-50 microns. ¡ Simultaneous, side-by-side delivery of both fluorescein and ICG an-
l Used to evaluate the structural details of the anterior segment struc-
giographies
ture, iris angle ciliary body, lens zonules. ¡ Single images can be captured at up to 20 frames per second with
l Useful in assessing angle, iris and trabecular meshwork relationships
512 x 512 resolutions.
in eyes with corneal edema and corneal opacity ¡ Acquires upto 12 frames-per-second with a resolution of 256 x 256
l Measurement of angle in ACG, OAG, checking patency of PI
Glaucoma pixels. providing real time high speed angiography

SWAP [Short wave automated perimetry (blue on yellow perimetry)] Optical Coherence tomography (OCT)
l Evaluates the blue cones that are lost early in glaucoma l Non contact, non invasive tool
l Uses yellow background and blue stimulus to selectively stimulate l Uses low coherence near infrared light 830nm
l Resolution 10-15µm, field of view 300, requires pupillary dilatation
the blue cones
l Advantage: detects the glaucomatous VFD earlier than standard and clear media
l Based on Michaelson interferometer.
white on white perimetry. l Uses: macular thickness assessment in
l Uses: early diagnosis of glaucoma, early detection of progression,
v Diabetes,
predict the risk of conversion of OHT to glaucoma v ARMD,
l Drawback: nuclear sclerosis and cataract may mimic early progres- v Cystoid macular edema,
v Macular hole,
sion on SWAP v CSR
l In glaucoma
Frequency doubling perimetry (FDP) v Optic disc tomography
l Detects early loss of the Nonlinear M-cells (a subset of magnocellular v Retinal nerve fibre layer thickness measurement

cells) Parul Sony, MD
l Based on frequency doubling illusion(high temporal and low spatial Dr. R.P. Centre, AIIMS, New Delhi - 110029

frequency)

December, 2003 285 DOS Times - Vol.9, No.6