Tips on Retina Practice

-Learn about 1-2 IS more (mostly
antimetabolites) & use them in practice.
-Broadly 4 groups...

1. Antimetabolites- MTX, Azathioprine
(Imuran) & Mycophenolate mofetil (MMF).

2. Alkylating agents- Cyclophosphamide
& Chlorambucil.

3. T-cell inhibitors- Cyclosporine &
Tacrolimus

4. Biologics- Infliximab & Adalimumab.
-MTX cheapest & safest in children (Not
pregnancy). Start with 7.5 mg once a week.
Imuran started with 1mg/kg/day & increase
gradually till 2mg/kg/D.
-Biologics are costly, long term safety
unknown. TNF inhibitors especially
reactivate latent TB.

Tip-178.....
Conventional retinal lasers have each laser
Pulse of few milliseconds (e.g.
100msec/0.1sec), while Micropulse laser has
pulse duration of Microseconds (100-300).
Hence Micropulse laser produces...
- Subthreshold spot (clinically invisible).
Thus, application is difficult to monitor.
-Burn confined to RPE (desired site of
treatment), thus no collateral damage (safer).

Tip-179....
Current treatment of CSCR (CSR).....

-Observe (self resolving in 8-12 weeks)
-Stop steroids in any form (reduce, if not so
feasible)
-Life-style change?
NEWER/present treatments of Chronic or
Recurrent CSCR.....
NO definite treatment till today, however
following tried....
1. Anti-corticosteroid- Mineralocorticoid
antagonist e.g. Eplerenone (25/50 mg OD/
Anti-HT drug available as 25 mg tablet, can
cause hyperkalemia) & Spironolactone.
2. Anti-Helicobacter pylori antibiotics. H.
pylori produces cytotoxins damaging
choroidal vessels.
3. Anti-VEGF- useful only if associated
with CNVM.
4. Retinal laser- for leaks outside FAZ.
5. PDT with reduced fluence (power).
6. Subthreshold Micropulse laser- (see Tip-
178) better than conventional laser. Safer for
fovea.

Tip-180.....
White dot syndrome comprises a group of
posterior uveitis disorders which are
generally B/L (except MEWDS), idiopathic
& affecting young or middle aged (except
Serpiginous/any age & Birdshot
choroidopathies/ 40-60 years aged females).

Serpiginous choroiditis (GHPC) is a type of
White dot syndrome which has
morphologically similar Tubercular
(infective) variant.
Unlike classical Serpiginous choroiditis,
Tubercular variant (Multifocal Serpiginoid
choroiditis/MSC) is/has...
-lesions not starting in peripapillary region,
but away from disc & spreading to far
periphery.
-smaller, less confluent & multifocal lesions.
-associated vitritis more.
-may be U/L.
-responds to ATT with short steroid course.

Tip-181....
Active chorioretinitis lesions are white to
yellow in colour with fuzzy margins &
sometimes mildly elevated, while healed
lesions appear dull & greyish with
pigmentation & discrete margins.
Both may coexist.

Tip-182.....
Always think of Fungal Endogenous
Endophthalmitis (FEE), if in seriously ill
hospitalized patient on multiple tubes (IV,
catheter, drainage tube, etc.), on fundus
examination, shows ill-defined creamy-
white lesions in retina; irrespective of

whether he is asymptomatic or having red
and painful eye.
-Candida is the most common cause
followed by Aspergillus. (Follow Tip-183).
Opposite with Exogenous endophthalmitis.
-Although rare, FEE is commoner than
Bacterial EE.
-Infection is blood borne, indicating
fungemia.
-Diagnosis is mainly clinical. Also by fungal
identification in smear, PCR or culture of
specimen from vitreous/aqueous. Also from
blood, etc.
-Mainstay of treatment is systemic
antifungals- IV/oral for 4-6 weeks.
Intravitreal & PPV only if not responding or
significant vitreous involvement.
-Voriconazole (2x200mg tab BD) is the first
choice (systemic & I-Vit inj.), being broad
spectrum & safer followed by
Amphotericin-B (nephrotoxic & poor
intraocular penetration) & Caspofungin.
Exogenous fungal endophthalmitis unlike
Endogenous involves vitreous first & then
retina (latter being of hematogenous origin).

Tip-183....
Fungal endogenous endophthalmitis (FEE)
is most commonly caused by Candida
followed by Aspergillus.

In FEE, Aspergillus lesions unlike those of
Candida....
-start at macula
-spread subretinal first, then vitreal.
-spread faster than of Candida.
-Angioinvasive causing hemorrhagic
infarcts.
-'String of pearl' appearance in
retina/vitreous is classically seen with
Candida.

Tip-184......
Geographic atrophy (GA) unlike Non-
geographic atrophy (RPE
degeneration/Incipient atrophy) of AMD
is/has:
-advanced form of AMD (other advanced
form is Neovascular AMD.
-discrete (well-defined) borders.
-underlying choroidal vessels become
visible
-Never develops CNVM, but develops
vision loss due to foveal atrophy.
-FAF is the gold standard for monitoring
progression (loss of RPE autofluorescence).
However, both are dry forms of AMD &
have no role of nutritional supplements as
per AREDS-2 (See Tip-64).

Tip-185....
Focal ERG is not used clinically. Used only
in research. (see Tip-169)
Multifocal (Mf) ERG is for focal macular
diseases (tests macular cones only)
Full-field (ff) ERG is a mass response from
outer retina i.e. photoreceptors & bipolar
cells mainly (central, mid & peripheral
retina) and NOT the ganglion cells.
Unlike conventional (ff) ERG, Pattern
ERG....
1. Uses sine-wave gratings or checker-board
instead of flash.
2. Pupils are not dilated.
3. Contact lens electrodes are avoided .
4. Mainly for Ganglionic cell activity, hence
used in glaucoma also.
5. Has 3 deflections: N35, P50 & N95. N95
is negative deflection occuring at 95
milliseconds of stimulus & is from ganglion
cells & macular cones. If P50 is OK, but
N95 is defective, means ganglion cell
disease.
So to apply into clinical practice, one has to
know which retinal disease affects which
retinal layer or portion primarily.

Tip-186....
Waveforms in VEP are different from those
of mf (Multifocal) ERG. In VEP/VER also,
N1, P1 & N2 deflections occur & are

generated from entire visual pathway
(ganglion cells to occipital cortex) & occur
at 70, 100 &155 milliseconds respectively
(latency time from giving the stimulus),
while in pattern ERG, N1, P1 and N2
deflections occur at 35, 50 and 95
milliseconds respectively & are generated
by ganglion cells and macular cones.
VEP is non- localising (mass response from
entire visual pathway); although macula is
over-represented in the visual cortex, VEP is
more sensitive to optic nerve pathologies.

Tip-187....
Serpiginous choroidopathy (Geographic
helicoid peripapillary choroidopathy,
GHPC) unlike APMPPE (Acute posterior
multifocal placoid pigment epitheliopathy)
lesions:
1. Start in peripapillary region (occasionally
macular)
2. Confluent
3. Spread outward (creeping) at edges.
4. Chronic & recurrent
5. Activity & healing continues together.
While APMPPE lesions occur in young
adults, are non-recurrent, multifocal & non-
creeping, self curing in 3-6 months.

Tip-188....
In Hypertensive retinopathy grade-4 unlike
CRVO:
1. Changes bilateral (B/L CRVO is rare, but
possible; look for thrombo-embolism,
systemic vasculitidis & hyperviscosity
syndromes).
2. Less hemorrhages (extensive in CRVO)
3. Exudation more (both hard & soft). Less
in CRVO, that too only soft.
4. Arterioles primarily affected (extensive
venous engorgement & tortuousity in
CRVO).

Tip-189.....
Five most important retinal diseases that
have totally Extinguished ERG are
(remembered by an acronym- DOLAR):
1. Detachment of retina
2. Ophthalmic artery occlusion (see Tip-27)
3. Leber's Congenital Amaurosis (see Tip-
139)
4. Aplasia of retina
5. RP (severe form)

Tip-190....
CMV retinitis unlike ARN (Acute retinal
necrosis by Herpes) has:
1. No vitritis
2. Extensive hemorrhages (Pizza-pie or
Cottage cheese with ketchup appearance).

3. Mainly posterior pole & venous
involvement (mid-peripheral & arterial in
ARN).
4. Slow progression
5. Occurs in immuno-compromised only
(ARN possible in immunocompetent also).

Tip-191.....
Facts about Microperimetry:
1. Primarily for macular diseases (no
macular fixation compulsory unlike
conventional perimetry).
2. Tests macular sensitivity with
simultaneous fundus examination &
correlation, thus testing both macular
structure and function simultaneously at
various points in macula.
3. Uses spectral OCT or SLO & Eye-tracker.

Tip-192.....
AZOOR (Acute Zonal Occult Outer
Retinopathy) is a rare type of White dot
syndrome (see Tip-180) that affects Outer
Retina (photoreceptors-RPE) Zone-wise &
Acutely with vision or field loss but only
subtle (Occult) fundus findings initially.
Etiology-? Autoimmune or viral. Commoner
in young females.
Presents with acute scotoma & photopsia.
Abnormal ERG is characteristic.
Treatment is ? Try steroids.

Tip-193......
Typical Neuroretinitis is unilateral,
idiopathic optic disc edema with macular
star. Usually self limiting and non-recurrent.
Treatment- empirical with systemic
steroids/antibiotics.
While DUSN (Diffuse unilateral subacute
neuroretinitis) is caused by Nematode in
young people. Look for worm, whitish
subretinal spots & tracks with RPE mottling.
Treat by direct laser (to kill nematode, if
located) or Albendazole with steroids.

Tip-194....
Zaltrap is now being used off-label (1.25 mg
in 0.05 ml) by retinologists as intravitreal
anti-VEGF injection, as it is longer acting
(bimonthly injection after 3 monthlies),
costs much cheaper than Eylea & even
Avastin ultimately & also more efficacious
in some resistant CNVMs/DDME.
Aflibercept (earlier called VEGF Trap-eye)
molecule is FDA approved for eye use (as
iso-osmolar Eylea/ 2mg in 0.05 ml injection
vial) & colo-rectal cancer (as hyperosmolar
Ziv-aflibercept/ Zaltrap 4ml vial of
25mg/ml).
Both made by Regeneron Co., USA with
different collaborators.

Tip-195....
Increasing levels of Lipofuscin (wear & tear
yellow-brown autofluorescent pigment of
our body including eye) in RPE occurs not
only with aging, but also in AMD &
particularly Stargardt (causing „Silent‟
choroid on FFA -see Tip-142). Also seen in
Cone & Best's dystrophy & Retinitis
pigmentosa.

Tip-196....
Most consistent bad biomarker (on SD-OCT
scan) most closely associated with poor
visual acuity in DR, DME, CME, ERM &
MacTel is 'Disorganisation of Retinal Inner
Layers' (DRIL).
DRIL is inability to differentiate boundaries
of inner retinal layers viz. OPL, INL, IPL &
GCL, because of ischemic damage to
capillary plexuses.
Persistence or improvement of DRIL with
anti-VEGF also decides the visual
prognosis.

Tip-197....
Tips on Smartphone fundus photography-
-Needs smartphone (with flash light coaxial
with camera's lens), +20/28 D lens &
optional camera App (e.g. FiLMiC Pro- paid

app for iOS & Android, INR 1300/) to
adjust exposure, zoom & light intensity.
-Especially useful in tele-ophthalmology &
emergency rooms.
-Needs pupillary dilatation, clear media,
continuous flash light & patient's
cooperation.
-Patient looks far with other eye, keep phone
in video mode with flash on.
-20D lens is kept 4-5cm (2") from eye (i.e.
farther than in indirect ophthalmoscopy) &
phone at ~20cm from lens.
-Retina seen only if camera, handheld lens
& patient's pupil are aligned.
-Image is inverted like in I/O.
-For larger field, move 20D away from
patient or phone towards the patient.

Tip-198.....
Senile changes in retina:
-Decrease in photoreceptors
-Decrease in melanin granules in RPE.
-Increase in lipofuscin granules.
-Basal laminar deposits form (sheet like
deposits between RPE & Bruch's).
-Decrease in choriocapillaris & choroidal
flow.
-Drusen form (between RPE & Bruch's), but
not the large/soft ones.
-Arteriosclerosis of retinal vessels.

-Peripheral retinal degenerations increase
e.g. Cystoid, Paving-stone & Lattice.

Tip-199.....
In diabetic retinopathy, retinal capillaries
and venules are primarily affected, while
Hypertensive retinopathy affects retinal
arterioles primarily.

Tip-200......
RPE Rip/tear is...
-Sudden disruption of RPE in area of PED
with scrolling on itself.
-Most commonly seen in AMD either
naturally or after laser/Anti-VEGF injection.
-Dreaded complication (like
endophthalmitis) after Anti-VEGF inj. in
AMD, causing sudden loss of vision,
especially if fovea gets involved.
-Risk factors include large PED in diameter
& high PED (especially if >550mn)
-OCT is best for confirmation of diagnosis
& shows break in hyper-reflective RPE band
with scrolled & wavy RPE in PED.
-No known treatment for Rip, but Anti-
VEGF treatment for AMD can be continued.

Tip-201.....
Retinal break without SRF can be lasered
(barraged) alone safely. With small SRF
around retinal break, cryopexy alone is

better & may suffice, without requiring full
RD surgery.

Tip-202....
Pneumatic retinopexy (intravitreal gas
injection) may be tried in retinal detachment
with single, superior break in phakes
without any PVR.
Patients with uncontrolled glaucoma or
those who can't maintain posture for 5 days
should be avoided.

Tip-203.....
Hyperfluorescence (HF) on FFA is because
of any of the 2 basic reasons:
1. Transmitted- HF starts in early phase but
decreases in late phases.
2. Leakage- HF continues to increase in late
phases.

Leakage is called Pooling if HF occurs in
predefined space & Staining, if HF is from
scar/tissue.

Tip-204....
In 2018, US FDA approved the first cloud
based DL (Deep Learning) algorithm linked
to the fundus camera, that could identify the
eyes with diabetic retinopathy, that required
referral to an ophthalmologist.
DL is a type of Artificial intelligence based
on computer neural network that analyzes a

large data base & detects an outcome of
interest.

Tip-205......
Fuch's heterochromic iridocyclitis is the
only chronic anterior uveitis, that doesn't
form the posterior synechiae.

Tip-206.....
With +20D lens on I/O, one gets the ~50*
field (For meaning of degree in retina, see
Tip-11) & 3x magnification; while it is
~65*/2x with 30D. Working distance
decreases with increasing power (2"/50 mm
for 20D, 30mm for 30D).
Panretinal 2.2 gives ~65*/2.7x & 40mm
distance.

Tip-207....
Hyper-reflective Dots (Foci)/HRDs on SD-
OCT unlike hard exudates in DR cause no
shadowing. Also HRDs can occur in all
retinal layers and disappear fast with anti-
VEGF or anti-inflammatory treatment.

Tip-208.....
Vitamin-D deficiency has been linked
(empirical) to uveitis, ARMD, Thyroid eye
disease, DR and dry eyes. Vitamin-D acts as
anti-oxidant, scavenging free radicals. For
Indians, half an hour of exposure of mid-day

sun twice a week (without sunscreen) is
sufficient to prevent Vitamin-D deficiency.
Older people manufacture less of Vitamin-
D. Vitamin-D3 (Cholecalciferol) is better
than D2 (Ergocalciferol).

Tip-209....
To simplify & predict the long term visual
acuity after an eye injury, "Ocular trauma
score" has been given that includes 6
presenting prognostic factors: Visual acuity,
Endophthalmitis, Globe rupture, Perforating
injury, RD, RAPD.

Tip-210......
On FFA, if leakage from retinal vascular
endothelium is pronounced, cystoid spaces
in CME may fill rapidly; while if leakage is
small, cystoid spaces may fill very late in
angiogram. Thus cystoid spaces continue to
appear dark (hypofluorescent) in initial
stages.

Tip-211.....
Cone dystrophy could be either stationary or
progressive. Stationary variety has
congenital/Infantile onset & causes pure
cone dysfunction, while progressive variant
starts later & also involves rods.
Next Generation Sequencing (NGS) is the
most advanced technique that helps to

identify the defective genes in genetic
disorders like Cone dystrophy.

Tip-212.....
In a case of Diabetic retinopathy, presence
of disc edema and macular star usually
indicates coexisting Hypertensive
retinopathy.

Tip-213.....
CMV retinitis is commoner in patients of
HIV with CD4 (T- Helper cells) counts
below 50 cells/mm3. Normal count is 500-
1500 cells/mm3.
CMV retinitis is the most common
opportunistic ocular infection in AIDS.

Tip-214.....
Aflibercept (Eylea) binds to all forms of
VEGF-A with greater affinity than Bevaci &
Ranibi-zumab. It also binds to VEGF-B &
Placental growth factor.

Tip-215.....
In a case of unilateral retinitis pigmentosa
like picture, always rule out DUSN (Diffuse
unilateral subacute neuroretinitis)- caused by
nematodes.

Tip-216......
On USG-B Scan, in Choroidal melanoma,
internal reflectivity is low while height to
base ratio is high unlike Choroidal
metastasis.
Choroidal metastases are typically yellowish
(amelanotic) elevated lesions with SRF &
indicate widespread metastases and poor
prognosis.

Tip-217.....
Juvenile idiopathic arthritis/JIA (formerly
called Juvenile rheumatoid arthritis/JRA) is
the most common cause of uveitis in
children (<16 years). Risk factors for
developing uveitis in JIA include younger
age of onset, girl, oligo-articular
involvement & ANA positivity.
Commonly asymptomatic with bilateral,
non-granulomatous anterior uveitis &
commonly causes cataract.
Control with steroids/cycloplegics.
Immunomodulators (e.g. MTX) tried if
above fails.

Tip-218......
Retinal whitening in Commotio retinae
(blunt closed globe trauma) is due to
disruption of photoreceptors' outer segments
& not due to extra-cellular edema, as there is

no breakdown of blood-retinal barrier &
retinal blood vessels remain intact.
Usually, self resolving in majority &
steroids have a doubtful role.
It is called Berlin's edema, if macula is
involved.

Tip-219......
Hard drusen (<63 mn, as per AREDS)
fluoresce early on FFA (due to overlying
RPE atrophy), while Soft drusen (>125 mn)
hyperfluoresce later. Soft drusen (see Tip-
62) form a risk factor for CNVM.
To clinically judge the size of drusen,
compare it with the width of Central retinal
vein, which is also ~125mn.

Tip-220.....
In CRAO, BRAO, Cilio-retinal AO,
sometimes embolus in artery may be visible,
which could be..
1. Fibrin-platelet embolus in majority of
cases. Dull, grey-white & longer. These
move faster (mobile) & may move
spontaneously allowing vessel to open. Also
these are frequently associated with
amaurosis fugax.
2. Cholesterol/Hollenhorst plaque- shiny
yellow embolus.
3. Calcific- large white plaque. Least
common & are of cardiac origin.

Emboli are of either carotid (mostly) or
cardiac origin.

Tip-221.......
In a suspected retinal hole in retinal
periphery, always rule out ABC i.e.
A(e)nclosed oral bay, Blot hge & Cystoid
degeneration. Indentation helps (see Tip-73).

Tip-222.....
White spots in retina:
1. Hard exudates- whitish-yellow, waxy,
deeper (in OPL) than soft, distinct margins,
no vitreous cells.
2. Soft exudates- whitish, superficial,
feathery margins, no vitreous cells.
3. Drusen- round/oval, whitish/yellowish
colour lesions.
4. White dot syndromes- are inflammatory
chorioretinopathies. Always look for
vitreous/retrolental cells.
5. Heredomacular dystrophies- bilateral &
commonly symmetrical lesions (see Tip-96).
6. Etc.

Tip-223....
Most common manifestation of drug toxicity
(e.g. to CQ, HCQ, PTZ, etc.) to retina is in
form of pigmentary maculopathy. Classical
presentation (but not the earliest) is Bull's
eye maculopathy with fovea surrounded by

depigmented ring followed by ring of
hyperpigmentation.
Earliest clinical signs are non-specific and
include loss of foveal reflex & macular
mottling (RPE in different shades). FAF &
Mf-ERG are most sensitive & can detect
changes before the fundus changes develop.

Tip-224........
Incidence of NVG is more in those cases of
PDR who have undergone vitrectomy or
cataract extraction, as this leads to greater
entry of vaso-proliferative factors into the
anterior segment.
NVG in diabetic retinopathy (DR) indicates
poor systemic prognosis with >20%
mortality rate.

Tip-225....
CSR (CSC) is NOT the macular edema, as
the fluid collection in macular edema is
intraretinal (within the neurosensory
retina/NSR), while it is subretinal (beneath
NSR or RPE/SubRPE/PED) in CSR.

Tip-226......
Always rule out the peripheral retinal
capillary hemangioma (isolated or part of
VHL syndrome) in a young patient with
unexplained macular edema.

Tip-227.....
During normal retinal development, retinal
vessels starting from optic nerve head reach
nasal ora by 36 weeks & temporal ora by 40
weeks i.e. later.

Tip-228.....
In Purtscher (post-traumatic) & Purtscher
like retinopathy (non-traumatic) (See Tip-
151), pathognomonic features are Purtscher
flecken, which are retinal whitening patches
(looking like soft exudates) with uninvolved
centrally running retinal vessels.
Soft exudate unlike Purtscher flecken
involves the RNFL only, while the latter
extends deeper. However both indicate
capillary occlusion. Flecken usually resolves
in weeks to months and the treatment is of
no proven value.

Tip-229......
In CRAO (see Tip-132), Cherry red spot is
due to axoplasmic stasis & swelling of
ganglion cells which are absent in fovea,
while Cattle-trucking (box-carring) is due to
segmentation of blood column in retinal
vessels.
Both may take few hours to develop after
CRAO.

Tip-230....
In MacTel (PFT)/Macular telangiectasia on
OCT, hyporeflective cystic spaces , looking
like edema occur in outer retina (ONL), but
there is no increase in retinal thickness; as
there is no edema but rather loss of ONL &
ellipsoid zone.
Type-2 variant of MacTel is most common
& is an acquired bilateral condition seen in
middle aged with DM & HT as risk factors.

Tip-231......
AV nicking is the hallmark of chronic
Hypertensive retinopathy. In this, retinal
vein becomes less visible or even disappears
on either side of artery at its crossing.

Tip-232.....
On OCT scan, hyper-reflectivity &
increased thickness of inner retina indicates
either acute inflammation or infarction (e.g.
in acute CRAO) of retina.

Tip-233....
Cone dystrophy is either-
1. Stationary- early onset (infantile) & has
pure cone dysfunction.
2. Progressive- later onset & also involves
rods.
Molecular genetics (especially Next
Generation Sequencing, NGS - available in

India for INR 20,000/ & above) helps to
exactly differentiate.

Tip-234.....
Intraoperative OCT in Eye/VR surgery:
-SD-OCT built in the microscope itself i.e.
microscope integrated (MIOCT).
-Useful for transparent/very thin structures,
not easily visible with microscope, thus
useful for membrane (ERM, ILM, etc.)
peeling & lamellar corneal surgeries (e.g.
DMEK).
-Foot or assistant operated, providing real
time OCT imaging.
-Available from Haag-streit (iOCT), Zeiss,
Leica (also hand- held), etc.
-Now also integrated with 3D visualisation
systems (see Tip-235).
-Used by Neuro, ENT, vascular surgeons
also.

Tip-235....
3D viewing in VR/AS surgery:
-surgeon performs by not looking through
eye pieces of microscope but on panel
display (heads-up)- large HD monitor.
-Either Active system (e.g. Sony HMS/
Head mounting system)- viewing by
electronic glasses or Passive (e.g.
Ngenuity/Alcon, Artevo 800/Zeiss & True
vision)- viewing by 3D polarised glasses.

-Provide better & higher: depth of focus,
resolution, illumination, magnification &
delineation. Also less backaches for
surgeons (superior ergonomics). But less
comfortable for assistant.
-Great teaching tool, sharing same screen for
whole watching team (assistant/teacher can
opine better).

Tip-236....
Argus-II Retinal implant (prosthesis):
-FDA approved for severe Retinitis
pigmentosa (RP) (2013).
-By US co. (Second sight medical products
Inc.)
-3 parts: Eye glass mounted camera, Video
processing unit (VPU) & Stimulator
(implanted on retinal surface i.e. epiretinal
after vitrectomy).
-Costs ~1.5 lakh US $ + surgical cost.
-Especially useful in RP, because only
photoreceptors damaged, while inner retinal
layers with ganglion, bipolar, amacrine &
horizontal cells remain intact.
-Bionic vision means artificial, functional
vision.
-Other Retinal bionic implants include-
Alpha-IMS (German), Prima (French), etc.
Both use subretinal implants.
-Maximum vision provided by any implant
is 6/160.

-For other blinding disorders (e.g. DR,
Glaucoma, optic atrophy, etc.), direct
cortical stimulation prosthesis are being
tried.

Tip-237......
Hard drusen have well defined borders,
while Soft ones have ill-defined margins &
have tendency to coalesce producing
drusenoid PED, which shows pooling on
FFA with leak not extending beyond its
margins. (See Tip-219)

Tip-238…
Acute Retinal Necrosis (ARN) &
Progressive Outer Retinal Necrosis
(PORN).....
-Together called "Necrotising herpetic
retinopathy".
-Majority by Varicella Zoster, less often by
Herpes simplex.
-ARN is basically acute retinal 'arteritis'
causing retinal infarcts (well
defined, whitish-yellow necrotic patches)
with vitriitis.
-Unlike ARN, PORN has NO vitriitis &
occurs in Immunocompromised host with
'rapid' progression.
-Diagnosis mainly clinical. Viral-PCR from
aqueous/vitreous samples.

-Prognosis- poor (>50% develop RD from
necrosis).
-Treatment- Antiherpetic (prevents
bilaterality)- Systemic (oral/IV of
Valacyclovir &/or I-Vit of Ganciclovir, with
oral steroids after 1-2 days of anti-viral in
ARN.

Tip-239....
During cataract surgery, aqueous commonly
gets contaminated by surface bacteria but
only rarely causes endophthalmitis, because
of fast aqueous turnover (fully replaced
within 2 hours); while bacteria introduced
into the vitreous (e.g PC break, I-Vit
injections) commonly results in
endophthalmitis as vitreous has no
regenerating power or turnover.

Tip-240....
Always rule out Sarcoidosis in a case of
panuveitis, if chorio-retinal lesions
(hypopigmented) are more in inferior half of
fundus.
Tip-241.... Fundus photos in FAF, FFA &
Red-free are black and white.
In FAF, both retinal vessels & optic disc
appear dark (see Tip-123); while on FFA
both appear white.
In Red-free fundus images, disc is white but
blood vessels are black.

Tip-242.....
Swept Source OCTA (SS-OCTA) is now
available commercially (e.g. Topcon).
Advantages of (SS-OCTA) over SD-
OCTA....
1. Higher wavelength (1050nm) (850 of SD-
OCTA), hence penetrates deeper through
RPE, picking type-1 CNVM better &
visualising choroid better (earlier possible
with ICGA only).
2. Faster scanning speed, allowing denser
scan patterns & larger scanned areas (wider
field- 12mm; 1mm~5*, see Tip-11) in a
defined time.
3. Longer wavelength is safer for eye
allowing higher laser power.
4. Media haze obstruction is less.

Tip-243.....
Anemic retinopathy occurs with low oxygen
carrying capacity of blood (Hb <6 gm%).
Causes hypoxia, thus affecting mainly
superficial retinal layers causing superficial
hemorrhages, soft exudates, retinal/macular
edema & occasionally subhyaloid
hemorrhage. Arteries are attenuated, while
veins are dilated & tortuous.
Treat the etiology & it resolves.

The term 'Retinopathy' is used only for
retinal diseases caused by systemic ailments
& NOT for exclusive retinal diseases.

Tip-244......
To diagnose peripheral retinal ischemia on
ophthalmoscopy, look for sclerosed retinal
vessels with dull greyish discoloration of
peripheral fundus background.

Tip-245.....
OCT uses low coherence interferometry
light. Why low coherence?
With low coherence (temporally), two path
lengths of lights are very nearly the same i.e.
within a micron or so. Thus in OCT, the low
temporal coherence allows distances to be
determined precisely down to the micron
level, enabling high resolution (axial
resolution of 1-10 micron) & high speed
imaging.
Resolution is much higher than USG
(typically 1mm with 3 MHz probe, 0.3 mm
with 10 MHz; higher resolution with higher
frequency, but lower penetration), but
approaching that of histopathological
section.
OCT is fibre-optic based, hence can be
interfaced to many instruments like
microscopes, endoscopes, catheters, etc.

Tip-246.....
In Eales' disease, retinal neovascularisation
directly correlates with the extent of
peripheral retinal ischemia. While NVD in
many uveitis cases can occur without any
ischemia; thus inflammation alone in many
uveitis cases can trigger neovascularisation.
Hence, it responds to steroids &
immunosuppressives.
Anti-VEGFs help only partially in these
cases, although VEGF remains the key
element in these cases.

Tip-247.....
In Chronic CSR:
-Silent type-1 CNV (sub-RPE) needs to be
ruled out on multimodal imaging (Swept
Source-OCTA is best as FFA & OCT
commonly fail in these cases).
- Definition: persistent symptoms of > 6
months or persistent SRF with RPE
epitheliopathy (atrophy, hypertrophy or
hyperplasia) & leakage on FFA.
- CNV especially occurs in those chronic
cases which show thinning of fovea, sub-
RPE deposits causing flat irregular PED &
increased choroidal thickness.

Tip-248.....
While bacterial culture detects only live
organisms, PCR detects both dead & live

bacteria without any differentiation. Hence,
PCR is much more sensitive than bacterial
cultures.

Tip-249......
In the definition of Posterior pole of retina
(fundus), Fovea forms the central point with
2 disc diameters (DD) of radius (i.e. 3mm);
while defining zones in ROP, optic disc's
centre is the central point (Zone-1 has 4DD
radius).

Tip-250.....
Postoperative endophthalmitis (bacterial)
usually starts after 24 hours, while
postoperative sterile inflammation (e.g.
TASS) starts within 24 hours of surgery.

---THE END ---

Fifth Edition

Complete and Unabridged