DOS Times_Sept-Oct 2019_Low Res

Basics

Figure 2: MN Read Test Score Sheet. because each sentence has the same length: Figure 4: showing typical shape of
10 standard length words. Reading speed MNREAD Acuity chart curve for normal,
Figure 3: Graph showing Reading Speed is given by: reading speed = 600 / (time in mild low and severe low vision subjects and
data w.r.t. logMAR print size. seconds) the critical print size shown by “diamond”.
down. This is the “critical print size”. If a
non-standard viewing distance (not 40 cm) A more precise reading speed measurement applications, such as a comparison with
is used, it has to be remembered to adjust the can be achieved by excluding words that an individual’s self-reported judgment of
critical print size to account for the viewing were missed or read incorrectly. In this case reading ability or performance on related
distance (i.e. if text is held nearer, then reading speed is given by: reading speed = 60 activities of daily living, as well as the
critical print size will come to lie in lower x (10 - errors) / (time in seconds) association with nonvisual variables, such
lines of text, as automatic magnification is as general health status or depression.
achieved by reduction of distance). If more than 10 errors were made, then An MNREAD Acuity Chart curve of reading
Measures of Reading performance reading speed can be assumed to be zero. speed vs print size has a typical shape for
Three measures of reading performance are normally sighted persons and many low-
obtained: The reading speed with print larger than vision individuals (Figure 4). This curve
Calculation of Reading acuity the critical print size is the maximum is characterized by 3 summary values. At
Reading acuity the smallest print that can reading speed. Maximum reading speed is large print sizes, reading speed remains
just be read; the reading speed when performance is not fairly constant, forming a plateau that
Calculation formula: Acuity= 1.4 - (sentences limited by print size. represents the maximum reading speed
x 0.1)+ (errors x 0.01) (MRS). As the print size decreases, a critical
Calculation of reading speed Determining the Critical print size print size (CPS) is reached at which reading
Reading speed is measured in words per speed begins to decline rapidly. Finally,
minute. With the MNREAD Acuity Charts Critical print size is the smallest print that the smallest print size that can be read is
the reading speed calculation is simplified supports the maximum reading speed defined as the reading acuity (RA). These 3
i.e. print size at which patients can read parameters of the MNREAD Acuity Chart
with their maximum reading speed. This curve have been used to summarize visual
is an important measure as it indicates reading function. They have been shown to
the minimum magnification required for have high test-retest reliability in normally
effortless reading. The critical print size sighted persons6.
is most easily identified from a plot of the The missing data is considered one which
patient’s reading speed at each print size. the subject cannot read after reaching the
reading acuity. It also includes large print
Reading Accessibility Index sentences which subject cannot read say in
conditions of a scotoma. The large sentences
A fourth measure called the Reading which are skipped are also included in
Accessibility Index has also been introduced missing data.
by Calabrèse et al.3 It is single-valued Multiple versions of the reading vision eye
measure that represents a person’s visual charts are available to provide variation
access to commonly encountered printed of sentence sets for examinations of the
material. left and right eye, in pre/post testing, and
where repeated testing is useful. The chart’s
It is given by level of effectiveness and accuracy has been
validated by scientific testing.
Mean reading speed (MRS) in words per According to the standard MNREAD Acuity
minute for largest 10 print sizes (0.4 to Chart scoring procedure, a reading speed is
1.3 logMAR) on MNREAD Acuity chart at computed for each of the 10 print sizes using
viewing distance of 40 cm/200. the measured reading time and the number

This range of print sizes is chosen for
two reasons. First, it sustains the MRS in
normally sighted persons.4 Second, it covers
most contemporary printed text found in
everyday life5. By using a normalizing factor
estimated from normally sighted young
adults, conventionally, reading accessibility
index of value 1.00 is kept for normal
performance. Thus a value of 0.00 means that
subject could not read any of the sentences
in the designated range. Values greater than
1.00 indicate persons who exceed the mean
of the normally sighted young adults. This
summary value can prove useful to measure
outcomes of clinical trials, to evaluate the
effectiveness of reading devices or reading
rehabilitation programs, and to study
the effect of viewing conditions, such as
light level. It could also be useful in other

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Basics

of errors. Occasionally, some print sizes will rehabilitation techniques7. Appropriate Vis. 2011;11:8.
not be tested, especially with low-vision rehabilitation programs can be used to 6. Subramanian A, Pardhan S. The
individuals. increase reading speed.
repeatability of MNREAD acuity charts
Conclusion References and variability at different test distances.
Optom Vis Sci. 2006;83:572-576.
As reported in a large study of children and 1. Deniz Altinbay, Fatih Mehmet Adibelli, 7. Calabrèse A, Cheong AM, Cheung SH, He
adults across a wide age range, 62% of the Ibrahim Taskin, and Adil Tekin. The Y, Kwon M, Mansfield JS, Subramanian
patients seeking low-vision consultation Evaluation of Reading Performance A, Yu D, Legge GE. Baseline MNREAD
were primarily interested in gaining with Minnesota Low Vision Reading Measures for Normally Sighted
improvement in personal reading7. Though Charts in Patients with Age-related Subjects From Childhood to Old Age.
optical correction is adequate for near Macular Degeneration. Middle East Afr Investigative Ophthalmology & Visual
VA requirements in low vision subjects, J Ophthalmol. 2016 ; 23: 302–306. Science July 2016, Vol.57, 3836-3843.
however, optical correction is inadequate
for improving reading performance. The 2. Owsley C, McGwin G Jr, Lee PP, Corresponding Author:
continuous-text MNREAD eye charts Wasserman N, Searcey K. Characteristics
extends the capability of eye examinations of low-vision rehabilitation services in Dr. Punita Kumari Sodhi MS
by measuring the reading acuity and the United States. Arch Ophthalmol. Guru Nanak Eye Centre and
reading speed. These extend past the reach 2009;127:681-689. Maulana Azad Medical College,
of traditional eye exams because of their New Delhi, India.
capability to measure the impact of eye 3. Calabrese A, Owsley C, McGwin G,
conditions on reading. Problems with Legge GE. Development of a reading
reading pose a major problem for most accessibility index using the MNRead
people with vision impairment. The other acuity chart. JAMA Ophthalmology.
traditional letter charts are designed to 2016;134 :398-405.
measure acuity and contrast sensitivity, but
do not provide direct information about 4. Legge GE. Psychophysics of Reading in
reading vision. Reading performance is Normal and Low Vision. Mahwah, NJ:
commonly used as an outcome measure Lawrence Erlbaum Associates Inc; 2007.
for clinical trials to assess the effectiveness
of treatments, surgical procedures, or 5. Legge GE, Bigelow CA. Does print size
matter for reading? A review of findings
from vision science and typography. J

50 DOS Times - Volume 25, Number 2, September-October 2019 www.dosonline.org/dos-times

Basics

Visual Acuity Assessment in
Children

1Smita Kapoor, 2V Rajesh Prabu, 3Swarna Udayakumar
1. Vision Eye Centre, Siri Fort Road, New Delhi, India.
2. Sankara Eye Hospital, Coimbatore, India.
3. Mahathma Eye Hospital, Trichy, India.

Abstract: Vision assessment in children is very challenging. It is time consuming and requires a lot of patience. However its importance lies
in the fact that it prevents amblyopia and helps in diagnosing other serious ocular anomalies. Children do not complain of visual problems
until they are much older. A routine evaluation is thus required and this article will highlight the time intervals at which vision should be
assessed.

Children learn to see over time just sensitivity improves at all spatial children become uncooperative when
as they learn to walk, talk, read and frequencies upto 10 weeks of age, thus approached for examination. To assess
write. The visual acuity of a newborn is suggesting the increase in length of the visual milestone of the child, the
less than 10% of an adult and by adult cones upto that age. Spectral sensitivity parents are asked if the child responds
criteria a newborn is legally blind. Visual in the light-adapted state is 10 times less to toys, lights or mother’s face. Past
deprivation in a child can adversely in a two month infant as compared to history include prenatal and perinatal
affect the brain that processes visual an adult due to shorter length of cones. trouble, mode of delivery, gestational
signals. The effect of visual deprivation Infants can differentiate between red age and birth weight. Family history
depends on the time at which the and white at 2 months of age as they of poor vision, strabismus and genetic
deprivation occurs. Visual deprivation have red, green and blue absorbing cone disorders should be taken. To assess
can occur in case of anisometropia, pigments similar to adults. Sensitivity the developmental milestones, Denver
ametropia, strabismus,congenital in dim light is 1 log unit below adults at Developmental Scale can be used. A
ptosis or cataract. This can lead to poor 3 months of age and rod photoreceptors rapport should be developed with
vision in one or both eyes as a result show a threefold increase in length. children by playing with them and
of changes in the brain (amblyopia). Dark adaptation is similar in infants entertaining them. Some children like
About 2% to 4% of the population can and adults concluding that the kinetics to be treated as adults and addressing
of the infant rod pigment are same them as sir/madam or asking direct
become amblyopic because of visual in both the age groups. Optic nerve questions reduces their anxiety during
deprivation in the early years of life. development is almost complete at examination. Different fixation targets
birth with minimal postnatal growth. can be used to examine the fixation and
Normal visual development The gradual maturation of the visual ocular motility. The key to a successful
Infants can see at birth. Astigmatism is system is attributed to the development paediatric examination is PATIENCE.
present at birth but infants can make of photoreceptors and synapses in the However, for uncooperative children
adjustments for objects at different inner retinal layers and myelination of examination under anaesthesia has
distances. Accommodative effort is not the central pathways. to be performed. In children less than
well established due to lack of need and 2.5 years chloral hydrate can be used.
ability. There is considerable ocular History and Physical Examination Older children require propofol or DPT
growth and retinal maturity after birth. Most of the history in children is (Demerol,Phenergan and Thorazine)
The properties of photoreceptors and obtained from the parents as children (Figure 1) Table 1.
the central visual system change as may not complain of blurred vision,
the ocular system matures. The eye squinting or diplopia. While talking Visual Acuity Assessment
is shorter in the new-born (16.8 mm) to the parents the physician can Visual acuity assessment can be divided
thereby making them hypermetropic, observe the child’s head posture, eye into preverbal and verbal age groups.
pupils are smaller and cone alignment and gross ocular anomalies. Preverbal: Monocular and binocular
photoreceptors are widely spaced (more Paediatric ophthalmologists refrain fixation should be tested separately.
than 6 µm) leading to image formation from wearing white coats as most Monocular fixation should be tested
on a smaller area on the retina. Contrast

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Table 1: Milestones related to vision

29th week of gestation Pupillary reflex

Birth Poor eyesight
Infant will blink in response to bright light
Eyes are sometimes uncoordinated, may look crossed-
eyed

1 month Looks at faces and pictures as fixation develops
Watches parent closely
Tearing begins

2 to 3 months Fixation, saccades and smooth pursuit well developed
Begins to see an object as one image
Figure 1: Different fixation targets for Looks at hands
examination. Follows light, faces, and objects
Smiles at smiling face
Figure 2: Central corneal reflex (Foveal Vertical tracking is elicited between 1 and 2 months
fixation)-Monocular.
4 to 5 months Blink response to threat (Menace Reflex)
Figure 3: Steadiness of fixation – Monocular. Accomodation appropriate to target, convergence and
for accuracy (good, fair, poor), location foveal maturation
(central,eccentric) and duration Achieving orthophoria
(maintained, sporadic). The CSM
method assesses the corneal centration, 5 to 7 months Has full color vision
maintainence of the centration and Stereopsis well developed
whether the eyes sustain alignment. Contrast sensitivity well developed
Eccentric fixation shows that the
fixation is not foveal and vision is less 7 to 11 months Can stare at small objects
than 20/200 (Figure 2-4). Plays peek-a-boo
Methods for assessment of visual
11 to 12 months Can watch objects that are moving fast

12 to 14 months Able to place shapes in proper holes
Becomes interested in pictures
Recognizes familiar objects and own face in the mirror
Points and gestures for objects and actions

18 to 24 months Optic nerve myelination complete
Able to focus on objects near and far
Can point to body parts (nose, hair, and eyes) when
asked

36 to 38 months Can copy shapes
Vision is nearing 20/20
Names colours

48 to 72 months (4 to 6 Has complete visual acuity and depth perception
years)

acuity in preverbal children include abnormal OKN’s, however a normal
optokinetic nystagmus (OKN), forced OKN only indicates that the macula
preferential looking (FPL) tests and is getting a good image of the stripes
visual evoked potential (VEP). OKN is a and the oculomotor pathway from the
short and simple procedure (Figure 5). retina to the brainstem and back to the
eye muscles is functioning properly.
An OKN drum is rotated in the field of It has several drawbacks. It requires a
child’s vision and the eye observed for child’s attention, lacks standardization
pendular ocular movements- first slow of speed of the rotating drum and poor
and then as the stripe disappears a fast correlation with Snellen-type visual
refixation to the next stripe. A number acuity, normal infants can have absent
of visual problems can generate OKN and patients with no visual cortex

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Table 2: Age-Related Visual acuity Estimates by different tests

Technique Birth 2 months 4 months 6 months 1 year Age for
20/20
OKN 20/400 20/400 20/200 20/100 20/60 (months)
FPL 20/400 20/400 20/200 20/150 20/50 20-30
VEP 20/800 20/150 20/600 20/400 20/20 18-24
6-12

Figure 4: Ability to keep the eye fixed
on a target when either eye is covered
(Binocular).

Figure 6: Cardiff Test.

Figure 7: Teller Acuity Card.

Figure 5: OKN Drum. There is lack of crowding phenomenon Figure 8: Visual Evoked Potential.
in FPL tests. The third test, VEP is a
can have a positive OKN response. summed cortical response that results absence of the occipital cortex and
Cardiff Acuity test is useful between from temporal change in the intensity cortical blindness. This may be due
6 months to 3 years. The Vanishing of the visual stimulus entering the eye to the contribution of the secondary
Optotypes are combined with the (Figure 8). visual cortices. The exact origin of the
principle of ‘Preferential Looking’ to waveforms generated in VEP is not clear
provide a paediatric test method that It is an EEG recording made from the (Table 2).
gives excellent accuracy of diagnosis occipital lobe in response to visual
(Figure 6). stimuli. There are two types of VEP Verbal (3-5 years)
However, as patients with amblyopia - flash and pattern reversal. It is the Older children can identify shapes and
have better near visual acuity FPL tests only objective technique to assess can be assessed by a number of tests.
give false high acuities in patients with the functional state of the visual These tests work on the principle of
both anisometropic and strabismic system beyond the retinal ganglion matching optotypes .
amblyopia. Teller Acuity Card test cells. Widespread clinical application
measures grating acuity rather than is limited as testing equipment is 1. Kay pictures and Allen cards: Quick,
resolution acuity (Figure 7). expensive and training is needed to easy and reliable
record and interpret responses. Also,
VEP has been recorded in patients with 2. Sheridan Gardiner Test: Most
widely used, the test can be done

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Figure 9: A. Sheridan Gardiner Test B. Figure 10: Lea symbols, Landot C and Tumbling E.
Allen cards C. Cambridge Crowding Card
Chart D. Keeler LogMAR E. Kay pictures. Figure 12: Bruckner reflex.

at 3 or 6 metres, main letters are Figure 11: Snellen’s Chart. colour deficiency can also be done by the
HOTV in different sizes. Farnsworth-Munsell 100 Hue testand
3. Keeler LogMAR and Cambridge used for this purpose because of the Nagel and Pickford anomaloscopes,
Crowding Card: Single or widely practical difficulties. In preschool age, but they generally are not required for
spaced optotypes are used. low contrast Lea symbols can be used children.
The single spaced optotypes and for school age children the Vistech
underestimate amblyopia but and Pelli-Robson contrast sensitivity isua e s in c i ren
crowding card requires the child to charts have been used successfully with The visual field extent in term-born
match one letter out of a group of children as young as 5 years of age. neonates is significantly smaller than
optotypes which is more accurate Colour vision in older children and adults. The
in amblyopia (Figure 9). The colour perception of the human eye horizontal extent of the visual field
4. Lea symbols, Landot C and is because of the presence of 3 different increases steadily from age 2 months to
Tumbling E (Figure 10). cones. Proper colour discrimination 12 months. Binocular and monocular
requires normal cone function. field extent is 90–95% of that in adults
Verbal > 5 years Impaired capacity to distinguish colours by age 1.5 to 4 years. The two important
Snellen’s Chart : Most widely used for can be congenital or acquired. The tests prerequisites for visual field estimation
vision assessment in verbal children used to assess colour vision are: Ishihara in children are attention and ability to
(Figure 11). Pseudo-isochromatic plates are based on steadily fix on an object. While testing
the principle of colour confusion. They visual fields in children it is better to
Contrast Sensitivity are extremely sensitive for red-green focus on areas of suspected visual field
Contrast sensitivity is the minimal defects. They come with an illiterate loss first and then proceed to other
amount of contrast required to form with geometric shapes that can areas.
resolve various sized objects from be traced with a finger. This design is
the background. Because the world useful for children who do not know For infants, confrontation test which
of the infant and young child is built numbers, though it still requires the is a variant of “preferential -looking” is
around global perceptions, rather than comprehension and fine motor skills used, in which the examiner observes if
attention to fine detail, it is likely that of a 3 to 4-year-old. Quantification of the infant shifts gaze when a stimulus
assessment of contrast sensitivity is presented. Once the child develops
would provide a more accurate estimate fixation, a central target is shown
of an infant’s or young child’s ability to and then slowly a peripheral target is
function visually than would a measure brought watching for a fleeting eye
of visual acuity. However, there are movement to the peripheral target.
no widely available validated tools for In this way all 4 quadrants can be
assessment of contrast sensitivity in checked. For preschool age children,
infants or preschool-age children.

In infants, measurement of contrast
sensitivity is possible using the pattern
VEP. However it is not being widely

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Table 3: Recommended Eye Examination Frequency for the Paediatric screening. J Ophthalmic Nurs Technol.
Patient Examination Interval 1997;16:68-73.
5. Graf MH, Becker R, Kaufmann H. Lea
Patient Age Risk-free At-risk symbols: visual acuity assessment and
detection of amblyopia. Graefes Arch
Birth to 24 months At 6 months of age At 6 months of age or as Clin Exp Ophthalmol. 2000;238:53-58.
recommended 6. Pelli-Robson Contrast Test and
Accessories. 1980;87108.
2 to 5 years At 3 years of age At 3 years of age or as 7. Mitchell M. Scheiman PA, Amos CS,
recommended Ciner EB, Marsh-Tootle W, Bruce D.
Moore, Rouse MW. Pediatric Eye and
6 to 18 years Before first grade and Annually or as Vision Examination. Am Optom Assoc .
every 2 years hereafter recommended 8. Nye C. A child’s vision. Pediatr Clin
North Am. 2014;61(3):495–503.
Table 4: AAO guidelines for correction of refractive errors in infants and 9. Martin L. Development of the Visual
young children Field. :25–32.
10. Donahue SP, Porter A. SITA visual field
Condition Refractive errors (Dioptres) testing in children. J Am Assoc Pediatr
Ophthalmol Strabismus. 2001;5:114–7.
Age<1 year Age 1-2 years Age 2-3 years 11. Salt A, Sargent J. Common visual
problems in children with disability.
Isoametropia Arch Dis Child [Internet]. 2014;99:1163–
8.
Myopia -5.00 or more -4.00 or more -3.00 or more 12. Hoyt CS, Nickel BL, Billson FA. Creig s.
hoyt, m.d., bonnie lynn nickel, m.d., and
Hyperopia (with no +6.00 or more +5.00 or more +4.50 or more frank a. billson, m.d. 1982;26.
manifest deviation) 13. Hemel LP and BVHS. Visual
Impairments: Determining Eligibility
Hyperopia (with esotrpia) +2.50 or more +2.00 or more +1.50 or more for Social Security Benefits . 2002. 368 p.
14. Chung YW, Park SH, Shin SY.
Astigmatism 3.00 or more 2.50 or more 2.00 or more Distant stereoacuity in children
with anisometropic amblyopia. Jpn J
Anisometropia (without strabismus) Ophthalmol. May 2017. doi:10.1007/
s10384-017-0518-9.
Myopia -4.00 or more -3.00 or more -3.00 or more 15. Kramer SG, Mcdonald MA. Diagnostic
and surgical techniques, assessment
Hyperopia +2.50 or more +2.00 or more +1.50 or more of visual acuity in toddlers. Surv
Ophthalmol. 1986;31:189–210.
Astigmatism 2.50 or more 2.00 or more 2.00 or more 16. Fulton AB, Hansen RM, Manning KA.
Measuring visual acuity in infants. Surv
clinical assessment can be done with include a documented visual acuity Ophthalmol. 1981;25:325-332.
confrontation techniques by asking assessment and ophthalmoscopic
the child to copy the number of fingers examination (Table 3) Corresponding Author:
on the examiners fingers and also
by Goldmann perimetryusing the Below are the AAO guidelines for Dr. Smita Kapoor
largest and brightest target (V4e ).Both refractive error correction in children Vision Eye Centre, Siri Fort Road,
Goldmann perimeter and automated (Table 4). New Delhi, India.
static perimetry can be done for school
age children. References
1. Wright K W, S.(2003), Pediatric eye
Recommendation for ocular
examination in children examination. Ann U Stout, Pediatric
ophthalmology and strabismus (pp 57-
All infants should be examined by 67).
6 months of age to evaluate fixation 2. Frankenburg WK. The Denver
preference, ocular alignment, and the developmental screening test. Dev Med
presence of any eye disease. An eye Child Neurol. 1969;11:260-262.
evaluation for infants and children 3. Camp BW, van Doorninck WJ,
from birth to 2 years of age should Frankenburg WK, Lampe JM.
include eyelids and orbits, external Preschool developmental testing
examination, motility, eye muscle in prediction of school problems.
balance, pupils and red reflex. Figure 12 Studies of 55 children in Denver. Clin
Pediatr (Phila). 1977;16(3):257-263.
Children older than 2 years should have doi:10.1177/000992287701600309.
two additional measures- vision testing 4. Hered RW, Murphy S, Clancy M.
and ophthalmoscopy. Eye evaluation Comparison of the HOTV and Lea
for children 5 years and older should Symbols charts for preschool vision

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Hess and Lees Screen

Gunjan Saluja, Asha Samdani
Dr. R.P. Center for Ophthalmic Sciences, AIIMS, New Delhi, India

Plotting deviations in patients with Figure 1: Hess chart degree, hence from the centre zero to
incomitant strabismus helps in the inner three squares mark 15 degree
assessing progression and planning dissociating the eyes. and outer square has an excursion of 30
treatment. The method of plotting the Patient wears a red green glass, with degree (Figure1).
field of action of paralytic muscle was red glaass in front of right eye first,
first given by Hirschberg in 18741, since and patient is given a green foster Principle
then various modifications have been torch, in this situation patient is fixing Hess screen is based on the haploscopic
made in the technique. Hess chart, Lees with right eye and pointing with left principle, that is two physical images
screen and Lancaster’s test are some of eye, in patients with pre-dominantly and one physiological image, patient
the tests used. horizontal deviations it’s easier to plot is presented with two separate images
with the help of a vertical line and in and is required to super impose the two
Hess Screen patients with pre-dominantly vertical images. Normal retinal correspondence
Hess chart was designed by Walter deviation, as in case of fourth nerve is required for the foveal projection
Rudolf Hess in 19082, the original test palsy its easier to plot with a horizontal of images and dissociation of eyes is
was constructed on a 80 cm* 80 cm line. The examiner presses a keypad to brought by red green glasses.
black cloth with embroidered red dots switch on a specific target while the
on the crossing of tangent lines, a 50 patient projects the green line with the The response generated in the Hess
cm long pointer with a green arrow help of foster torch and bisects the red chart follows the Herring’s law, and the
was used, patient was given red green dot. Since the red lights are an integral changes seen in the plot with the due
glasses which caused dissociation, after part of the screen, the goggles must course follows the course of changes
various modifications the modern day be reversed to obtain the plots for the seen in a paralytic squint, which are:
Hess Screen is the electronic version of opposite field. The response is plotted
a grey wall mounted screen scored on on a Hess chart, the chart consist of an 1. Under-action of the affected muscle
a tangent scale. Small red lights at the outer square and an inner square, each 2. Over-action of the antagonist of the
juncture where each scored line crosses small square on the chart measures 5
can be illuminated in turn by bulbs
located behind the screen. Lancaster’s
test is a modification of Hess chart,
which is less commonly used, and uses
a two dimensional screen instead of a
tangent screen3. Computerized version
of Hess screen and three dimensional
projection of the screen are some of the
recent modifications4,5 .

Plotting the Hess chart
The patient is made to be seated at
a distance of 50 cm, this distance is
essential to prevent the influence
of accommodative and proximal
convergence, the head is made immobile
using a head rest or chin rest. The test is
carried in a dimly illuminated room to
prevent the fusional cues, thus further

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Figure 2: Lees screen.

same eye Figure 3: Shows left third nerve palsy, note the under-action of superior rectus, medial rectus,
3. Over action of the yoke of the inferior rectus and inferior oblique, and over-action of ipsilateral antagonist lateral rectus
and superior oblique.
affected muscle Figure4: Shows right fourth nerve palsy, note the under-action in the direction of action of
4. Under-action of antagonist of yoke, superior oblique ( depression in adduction) and over action of ipsilateral antagonist inferior
oblique, causing over-elevation in adduction. Also note the over-action of contra-lateral yoke
spread of comitance muscles.
Lees Screen6
Plotting deviations with Lee’s screen

The Lees screen consist of two screens
placed at right angle to each other,
each of the screen can be illuminated.
The patient is seated at a distance of
50 cm and the patient’s head is leaned
on the chin rest which is present at
the end of the mirror septa dividing
the two screens, patient’s head must
be motionless during the procedure.
Both the examiner and patient are
given metallic wand. The examiner
than shows the patient a point on the
lighted screen and patient is asked to
superimpose the point on the unlighted
screen with the help of the metallic
wand given to him, the same procedure
is followed for the other eye. The
patient’s response is then plotted on the
Hess chart (Figure 2).

Principle
The dissociation in Lees screen is caused
by a two sided plane mirror septa, which
divides the two tangentially placed
screens.

Interpretation Figure 5: Shows left 6th nerve palsy, note the under-action of lateral rectus ,over action of
The interpretation of the test is based on medial rectus and over-action of the contra-lateral yoke, medial rectus.
the size, shape, position and deviation
of the plot.

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dimensional Hess screen test with
binocular dual search coils in three-field
magnetic system. IOVS 2001; 42: 660–
667.

5. Hirai T et al.: Dynamic aniseikonia on
Hess chart? Binocul Vis Strabismus Q
2004; 19: 234–245.

6. Lees VT: The Hess screen with mirror
dissociation. Br Orthopt J 1949; 6: 50–55.

Corresponding Author:

Figure 6: Shows left eye Brown’s syndrome, which is characterized by limitation of elevation
in adduction, with normal elevation in abduction and divergence in upgaze.

Dr. Gunjan Saluja
Dr. R.P. Center for Ophthalmic Sciences, AIIMS,
New Delhi, India.

Figure 7: Shows Left monocular elevation deficit, note the under-action of elevators, and over-
action of contra-lateral elevators.

The smaller plot is suggestive of the Common Hess chart plots
affected eye, central dot indicates Figure 3, 4, 5, 6 and 7 shows common
deviation in primary position. In larger Hess chart plots.
field maximum outward displacement
shows over-action of contra-lateral References
synergist, in smaller field outward
displacement in direction of ipsilateral 1. Hirschberg J: Über Blickfeld messung.
antagonist suggests contracture of the Arch Augen Ohrenheilkd 1874; 4: 273.
antagonist. Higher plot is suggestive
of hypertropia of that eye. Chart with 2. Hess WR: Eine Neue
sloping fields will be suggestive of A Untersuchungsmethode bei
and V patterns. Cases of restrictive Doppelbildern. Arch Augenheilkunde
squint will be suggestive of horizontally 1908; 62: 233–238.
or vertically compressed fields, with
marked over-action of contra-lateral 3. Lancaster WB: Detecting, measuring,
synergist. plotting and interpreting ocular
deviations. Arch Ophthalmol 1939; 22:
867–880.

4. Bergamin O, Zee DS, Roberts DC, Landau
K, Lasker AG, Straumann D: Three-

58 DOS Times - Volume 25, Number 2, September-October 2019 www.dosonline.org/dos-times

Photoessay

Lens Neovascularisation:
Neovascularisation on Intra
Ocu ar ens it Opaci e
Vitreous Imitating Vascularisation
on Total Cataract

Pooja Gupta DNB, Prafulla Sarma, Susmita Paul, Mayuri Borgohain, Shahinur Tayab, Chengchira Sangma
Sri Sankaradeva Nethralaya, Guwahati, Assam, India

Key words: Ischemic CRVO, neovascularisation on IOL, opticin, rubeosis iridis, vessels on lens, vitreous opacification.

An 80 year old female presented to Figure 1. Retina image showing ischemic CRVO with ghost vessels and tortuous veins. Optic
us with painful diminution of vision disc showing glaucomatous cupping, splinter haemorrhage and disc neovascularisation.
in left eye for 3 months. She was
diabetic and hypertensive and blood
sugar levels were not controlled. On
examination, left eye was pseudophakic
with a vision of projection of rays
inaccurate. Pupil was mid dilated and
not reacting to light. IOP was 60 mm Hg
with neovascularisation in all angles
resulting in secondary angle closure.
Retina examination showed ischemic
central retinal vein occlusion (CRVO)
with ghost arteries and tortuous veins.
Optic disc showed glaucomatous
cupping, haemorrhage and disc
neovascularisation (Figure 1). Diode
laser cyclo photocoagulation was done
to control pain and rise in IOP. Patient
was lost to follow up for 8 months.
After 8 months, patient presented with
no perception of light in left eye with
an IOP of 10 mm Hg. On examination,
the vitreous showed total opacification
pushing intraocular lens (IOL) in
anterior chamber leaving no space
between iris and IOL. This resulted in
arborising neovascularisation starting
from limbus, crossing iris and covering
anterior and posterior surface of intra-

www.dosonline.org/dos-times DOS Times - Volume 25, Number 2, September-October 2019 59

Photoessay

Discussion on icts o interest
There are no conflicts of interest.
Neovascularisation of cornea, iris, optic References
disc and retina is well documented1. 1. Shazly TA, Latina MA. Neovascular
However, adult human lens and its
capsule is avascular and resistant to glaucoma: etiology, diagnosis and
neovascularisation2. Glycoprotein prognosis. Semin Ophthalmol.
Opticin found in vitreous is also said to 2009;24(2):113–21.
have anti-angiogenic function3. In our 2. J.w. Mcavoy, e.g. Chamberlain, r.u.
case, the reason for neovascularisation De iongh, a.m. Hales, f.j. Lovicu.
over intra-ocular lens after cataract Lens development. Royal college of
extraction can be any of the following- ophthalmologists(1999) 13, 425-437 .
3. M.M. Le Goff; H. Lu; M. Ugarte; S. Henry;
Figure 2. Slit lamp image showing 1. Diabetes and ischemic CRVO M. Takanosu; R. Mayne, et al. The
total opacification of vitreous and iris leading to chronic hypoxia and vitreous glycoprotein opticin inhibits
neovascularisation extending over anterior high levels of vascular endothelial preretinal neovascularization. Invest
and posterior surface of intra-ocular lens. growth factors (VEGF) in anterior Ophthalmol Vis Sci. 2012;53(1):228–234.
chamber.
Figure 3. Slit section to show lens Corresponding Author:
vascularisation. 2. Anatomical proximity of intra-
ocular lens (Figure 2). This image is ocular lens with pupillary margin. Dr. Pooja Gupta
looking like vascularisation on total Sri Sankaradeva Nethralaya,
cataract which has never been reported 3. Loss of vitreous and its anti- Guwahati, Assam, India.
earlier to the best of author’s knowledge. angiogenic factors like opticin.

Declaration of patient consent
The authors certify that they have
obtained all appropriate patient consent
forms. In the form the patient has given
her consent for the images and other
clinical information to be reported in
the journal. The patient understands
that her name and initial will not be
published and due efforts will be made
to conceal her identity.

Financial support and sponsorship
Nil.

Rakesh Pandey

(Ocularist)

efore After

60 DOS Times - Volume 25, Number 2, September-October 2019 www.dosonline.org/dos-times

DOS Times Quiz

DOS Times Quiz

September-October, 2019
What is Best?

Prafulla K. Maharana MD, Farin Shaikh MD, Deepali Singhal MD
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.

The following Figure shows the ray tracing wavefront abberration of a 21-year-old male patient. What is the best method to
correct the refractive error of the patient?
• Wavefront optimized LASIK
• Wavefront guided LASIK
• ICL
• IPCL

Corresponding Author:

Dr. Prafulla Kumar Maharana
Dr. Rajendra Prasad Centre for Ophthalmic
Sciences, All India Institute of Medical Sciences,
New Delhi, India.

ANSWER

Answer _______________________________________________________________________________________________________________________________________
Name: ________________________________________________________________________________________________ Degree: _______________________________
Designation:_________________________________________________________________________ Address:_______________________________________________
_______________________________________________________________________ State _______________________________ Pin _______________________________
Mobile No: ________________________________________________________________________________________ DOS Membership no: ___________________
Email ID: _______________________________________________________________________________________Signature: ___________________________________
Email your answer to: [email protected]

www.dosonline.org/dos-times DOS Times - Volume 25, Number 2, September-October 2019 61

st

Delhi Ophthalmological Society

3rd - 5th April, 2020

Hotel The Ashok, Chanakyapuri, New Delhi

Ophthalmology

in 2020

and beyond...

HH H
De ates

ui
ree Paper
i e ur ery
ou Ask
e Answer essions
oun phthal olo ist ession

w w w. d o s o n l i n e . o r g

Tearsheet

Ocular Dimensions and Numbers

R.L. Sharma, Kalpana Sharma, Anubha Ojha
I.G.M.C. Shimla (H.P), India.

1. Orbit: Volume – 30cc, Depth – 40 -50 mm, Base width - 13. Anterior Chamber:
40mm, Base height -35 mm, Angle with central axis - 230, 1. Depth- 2.5- 3mm, Volume - 0.25cc;
orbital rim to corneal apex distance - 16-22 mm, orbital 2. Posterior Chamber - 0.06cc
fissure length - 22 mm 3. Aqueous turn over rate: 1% /min, Basal aqueous
secretion: 2.2 µL/min
4. Palpebral fissure: Length - 28mm, height - 8-10 mm, IPD -
55-70 mm 14. Anterior chamber angle - 300
1. Trabecular width: 0.8mm (AP)
1. Blinking rate -12-14 /min, blinking interval - 2-10 2. Schlemm’s canal diameter: 200-400µm long axis, 10-25µ
seconds short axis
3. Collector veins: 25-35 ., width: 20-90µm
2. Duration of blink - 0.3 second 4. Aqueous veins: 2- 8.
5. Cilia:
15. Iris: diameter -12mm, 0.5mm thick at root, 0.6 - mm at
1. Length - 10-15mm, collarette, area=110 mm2
2. Number: upper lid - 100-150 (3 rows), lower lid - 75-100
16. Pupil - 3-5mm, circular and nasal to optic axis
(2 rows) 17. Lens: Diameter- 9mm, Thickness - 4mm,
3. Rate of growth - 1 mm/week, life- 3 months
4. Meibomian glands - 1. Curvature- Anterior -10 mm, Posterior - 6mm,
2. Power - 17D,
1. Upper lid No. - 30-40, length - 5.5 mm, 3. Weight - 200mg
2. Lower lid no. - 20-30, length - 2 mm 4. Capsule- 4 µ - 22 µ thick (40micron)
6. Tarsal plate: upper - 25 x 10 x 1 mm, lower- 25 x 5 x 1mm 5. Refractive index -1.38
7. Conjunctival sac - volume: 35µL, one eye drop : ~ 50µL 18. Ciliary body - 0.3- 0.5 mm thick,
8. Eyeball- Weight- 7.5gm, Volume - 6.5cc, 1. Ciliary processes -70-80 in number,
Circumference-74.91 mm, 2. Blood flow=1ml/min, vol - 100µL
Diameter: 3. Average no. of contraction by ciliary muscle per day
1. Sagittal - 24.15 mm
2. Transverse - 24.13 mm -100000
3. Vertical - 23.48 mm 4. Number. of short posterior ciliary arteries/nerves: 7-20
9. Three coats of eye - 20 histological layers 5. Long posterior ciliary arteries/nerves: 2 -1 nasal, 1
2 - Conjunctiva and Tenon’s capsule
4 - Scleral layers - Episclera, Stroma, Lamina fusca, temporal
endothelium
4 - Uveal layers - Haller’s layer -large vessels, Sattler’s layer 19. Choroid- Thickness - 0.1- 0.5mm thick, blood flow -1ml/
- medium ves sels; Choriocapillaris; Bruch’s membrane, min
10 - Retinal layers - (RPE, photoreceptor, ELM, ONL, OPL,
INL, IPL, ganglion cell, NFL, ILM) 20. Vitreous: Volume - 4ml, weight - 4 g, Refractive index
10. Cornea- vertical - 11mm, horizontal - 12mm, 5 - layers -1.33
1. Thickness- 0.57 - 0.75mm, (E - 50 + BM- 10 + S 450 +DM-
10 + E -30 ) µ 21. Retina:
2. Power - + 42D, 1. Macula - 5.5 mm. Thickness- Perifoveal - 230 micron
3. Weight - 180 mg, 2. Fovea diameter- 1.5mm , Foveola -0.35mm, Foveal
4. Curvature - Anterior - 7mm, Posterior - 6 mm Avascular Zone- 0.5mm
5. Refractive index -1.37
6. Endothelium - 5 Lac (3000 - 5000 per mm2) 3. Number of rods -100 million, Cones – 5 million,
11. Limbus- 10 layers epithelium, White limbal zone -1mm pigment epithelium: 4.2- 6.5 million, Ganglion cells
wide, Blue limbal zone -1mm (superiorly), 0.8mm -1.2 million
(inferiorly), 0.4mm (temporally).
12. Sclera: Thickness-1mm, (0.3mm- insertion) (0.4 mm 4. Number of cellular layers - 4 (RPE, photoreceptor,
-equator) (1-1.35mm around optic nerve) bipolar, ganglion cell)

22. Optic disc: Diameter -1.5mm, C/D- 0.1-0.4, C/B index- 6-12
23. Optic nerve:

1. Length: 40mm –(Ocular-0.5 mm, Orbital-25mm, Canal-
10mm, Cranial-5mm)

www.dosonline.org/dos-times DOS Times - Volume 25, Number 2, September-October 2019 63

Tearsheet

2. Number. of fibres - 7,00,000 -1.2 millions, fibre diameter- 5.5 mm - zone free zone of anterior capsule, ideal
0.65 to 1.10 µm rhexis size.
10 - 10µ - Thickness of bowmen’s and Descemet’s
24. Lacrimal glands membrane, aqueous layer of tear 10 µl - Lacrimal lake
1. Krause’s gland - 40 upper & 8 lower volume
2. Wolfring gland- 2-5 upper lid & 2-3 lower eye lid 10 mm - Height of palpebral fissure in centre
10 mm- breadth of upper tarsal plate
25. Tear film -Basal tear secretion: 2µL/min, ph -7.6 10 mm -Lens anterior curvature
• Corneal tear film : 40µ thick (lipid;0.1µ, aqueous:10µ, 10 - anatomical layers of retina
mucin: 30µ), Refractive index: 1.357 10 - layers of epithelium at limbus
• Lacrimal lake volume - 7-10 µl, overflows if > 25µL/min 12- 12 - mm- Corneal horizontal diameter
• Meniscus radius (R) = 0.2 mm, tear film thickness (H) 12 - mm-Iris diameter
= 10 pm, meniscus width (H) = 0.1 mm, viscosity = 12 - Blinking rate/minute
11.3x10° 12 - lakh Ganglion cells
12 lakh optic nerve fibres
22. Lacrimal sac 15 -15mm- length of lacrimal sac
• Lacrimal puncta (lateral to med.canthus): upper-6mm, 15 mm- length of cilia
lower-6.5mm 40 -40µ- Corneal tear film thickness
• Lacrimal canaliculi: 0.5 mm dia, Length : Vertical part- 40 -Krause’s glands in upper eyelid
2mm, Horizontal part-8mm 100- 100 µl Blood volume in ciliary body.
• Lacrimal sac: Length-15mm (Fundus:3-5mm, body:10- 100 million no. of rods in eye
12mm), breadth- 5-6mm, vol- 20 cu.mm 1. A. Bron, R. Tripathi, B. Tripathi. Wolff’s Anatomy of the
• NLD: Length- 18mm (intraosseous part-12.5mm,
intrameatal part-5.5mm), diameter- 3mm Eye and Orbit, 8th Edition.
2. Leonard Levin Siv Nilsson James Ver Hoeve Samuel Wu
23. Extra ocular muscles (Recti)
• Distance from limbus (mm): SR-7.7, LR- 6.9, IR- 6.5, MR- Paul Kaufman Albert Alm Adler’s Physiology of the Eye
5.5 11th Edition; Saunders 2011.
• Length of tendon (mm): SR- 5.8, LR- 8.8, IR- 5.5, MR- 3.7 3. Carolyn Shea, Anatomy and Physiology of the Eye
• Width of tendon (mm): SR- 10.8, LR- 9.2, IR- 9.8, MR- Carolyn Shea, COMT 2010–2012,
10.3 4. Inessa Bekerman, Paul Gottlieb et al. Variations in
• Width of muscle (Recti): 9 mm Eyeball Diameters of the Healthy Adults journal of
• Levator palpebral superioris; 55 mm long, 3 insertions, Ophthalmology; Volume 2014, Article ID 503645, 5 pages.

24. Pituitary - weight -500 mg, 10.5 x 13.7 x 5.9 mm Corresponding Author:
Common digital values
1 - 1 - Normal AC/A ratio Dr. R.L. Sharma
I.G.M.C. Shimla (H.P), India.
1 mm/week - Eye lashes rate of growth
1% per minute of anterior chamber volume, the aqueous
turn over rate
1.5 - 1.5 mm - Fovea diameter
1.5mm – Optic disc diameter

2.5 -2.5 mm - Depth of AC,
0. 25 ml - Volume of AC

4 - 4µ-lens capsule thickness (4-22 µ)

0.4 mm - scleral thickness at equator
4 mm- lens thickness
4 cm- orbit base width
4 cm- optic nerve length

4 ml- vitreous volume
4 g- vitreous weight
4 - scleral layers, 4- uveal layers, 4- cellular layers of retina
5 -0. 5mm -Thickness of iris and choroid, Lacrimal canaliculi
diameter

5 - Layers of cornea
5 - Lakh corneal endothelium cells - 5 Lac

5 - million- cones

5.5 - 5.5 mm - MR insertion from limbus
5.5 mm - length of inferior rectus tendon
5.5 mm - distance of pars plana from limbus

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68 DOS Times - Volume 25, Number 2, September-October 2019 www.dosonline.org/dos-times

www.dosonline.org/dos-times DOS Times - Volume 25, Number 2, September-October 2019 69

DOS Travel Fellowship for Partial Financial Assistance
to Attend Conferences

Applications are invited for DOS Fellowship for partial financial assistance to attend conference(s).

Conferences
International: Eight fellowships per year.

• Maximum of Rs. 50,000/- per fellowship will be sanctioned

Partial travel fellowship to attend AIOC: Five fellowships per year

The last date of DOS Fellowship for Partial Financial Assistance to Attend Conference(s) for receiving application is 30th
September for National Conference.

Maximum of Rs. 10,000/- per fellowship will be awarded out to five one to the winner of the DOS best paper (A C Aggarwal
Trophy) for travel to present the paper in the forthcoming AIOC.

Eligibility
• DOS Life Members (Delhi Members only)
• 75 or More DCRS Points
• Accepted paper for oral presentation, poster, video or instruction course or invited guest speakers

Time since last DOS Fellowship
Preference will be given to member who has not attended conference in last three years. However if no applicant is found
suitable the fellowship money will be passed on to next year. Members who has availed DOS fellowship once will not be
eligible for next fellowship for a minimum period of three years.

Authorship
The fellowship will be given only to presenting author. Presenting author has to obtain certificate from all other co-authors
that they are not attending the said conference or not applying for grant for the same conference. (Preference will be given to
author where other authors are not attending the same conference). If there is repeatability of same author group in that case
preference will be given to new author or new group of authors. Preference will also be given to presenter who is attending
the conference for the first time.

Quality of Paper
The applicant has to submit abstract along with full text to the DOS Fellowship Committee. The committee will review the
paper for its scientific and academic standard. The paper should be certified by the head of the department / institution, that
the work has been carried out in the institution. In case of individual practitioner he or she should mention the place of study
and give undertaking that work is genuine for invited guest speakers & instruction courses only acceptance letter is required.
The fellowship committee while scrutinizing the paper may seek further clarification from the applicant before satisfying itself
about the quality and authenticity of the paper. Only Single best paper has to be submitted by the applicant for review (6
copies). Quality of the paper will carry 50% weightage while deciding the final points.

Poster and Video
The applicant will need to submit poster and video for review.

Credit to DOS
The presenter will acknowledge DOS partial financial assistance in the abstract book / proceedings.
The author will present his or her paper in the immediate next DOS conference and it will be published in DJO / DOS Times.

Points Awarded Points
1) Age of the Applicant 10
07
a) < 35 years 05

b) 36 to 45 years

c) 45 years plus

70 DOS Times - Volume 25, Number 2, September-October 2019 www.dosonline.org/dos-times

2) Type of Presentation 12
a) Instructor/ Co-instructor of Course 07
b) Free Paper (Oral) / Video 05
c) Poster
15
3) Institutional Affiliation 20
a) Academic Institution
b) Private Practitioner

4) The points awarded for DCRS rating in the immediate past year

a) > 150 10
b) 75 – 150 5
c) < 75 Not Eligible

Documents
• Proof for age. Date of Birth Certificate
Original / attested copy of letter of acceptance of paper for oral presentation / video / poster or instruction course /

invited talks.
• Details of announcement of the conference
• Details of both International & National Conferences attended in previous three years.
• Copy of letter from other national or international agency / agencies committing to bear partial cost of conference if

any.
• Original air travel boarding passes and photocopy of the attendance certificate of the conference.
• Fellowship Money will be reimbursed only after submission of all the required documents and verified by the

committee.
• Undertaking from the applicant stating that above given information's are true.
• If found guilty the candidate is liable to be barred for future fellowships.

Application should reach Secretary’s office and should be addressed to Chairman Travel Grant Fellowship Committee
before February 20, June 30, September 30 and December 30 for International Conference and National Conference.
The committee will meet thrice in a year in the month of August, November and February within 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.

Dr. (Prof.) Namrata Sharma
Secretary,

Delhi Ophthalmological Society
Room No. 479, 4th Floor,
Dr. Rajendra Prasad Centre for Ophthalmic Sciences,
All India Institute of Medical Scienses,
New Delhi – 110 029
Email: [email protected]

Obituary

Dr. A.C. Chadha (Past President) (1987-88) Dr. Santosh Chaudhry
29th July, 1932 - 7th January, 2020 5th March, 1957 - 8th January, 2020

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