Transcript Amblyopia - M M Joshi Eye Institute

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Unilateral or less commonly, bilateral
reduction of best corrected visual acuity that
can not be attributed directly to the effect of
any structural abnormality of the eye or the
posterior visual pathway.
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Resulting from one of following:
A.
B.
C.
Strabismus - DEVIATION
Anisometropia or high bilateral refractive
error (Isoametropia) - DEFOCUS
Visual deprivation - DEPRIVATION
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Prevalence: 2%-4%
Commonly unilateral
Nearly all amblyopic visual loss is
preventable or reversible with timely detection
and appropriate intervention.
Children with amblyopia or at risk for
amblyopia should be identified at a young age
when the prognosis for successful treatment
is best.
Role of screening is important
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Amblyopia is primarily a defect of central
vision.
There is a critical period for sensitivity in
developing amblyopia.
The time necessary for amblyopia to occur
during critical period is shorter for stimulus
deprivation than for strabismus or
anisometropia.
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Neurophysiology:
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Cells of the primary visual cortex can completely
lose their innate ability or show significant
functional deficiencies
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Abnormalities also occur in neurons in the lateral
geniculate body
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Evidence concerning involvement at the retinal level
remains inconclusive
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Classification:
1.
2.
3.
4.
Strabismus Amblyopia :Deviation
Anisometropia Amblyopia : Defocuss
Amblyopia Due to bilateral high refractive
error (isometropic) :Defocuss
Deprivation Amblyopia :Deviation
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Strabismus Amblyopia
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The most common form of amblyopia
Strabismic amblyopia is thought to result
from competitive or inhibitory interaction
between neurons carrying the nonfusible
inputs from the two eyes.
Which leads to domination of cortical vision
centers by the fixating eye and chronically
reduced responsiveness to the nonfixating
eye input.
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Anisometropia Amblyopia
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Second in frequency
It develops when unequal refractive error in the two
eyes causes the image on the one retina to be
chronically defocused.
This condition is thought to result:
Partly from the direct effect of image blur in the
development of visual acuity.
Partly from intraocular competition or inhibition
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Mild hyperopic or astigmatic anisometropia
(1.5D)  mild amblyopia
Mild myopia anisometropia (less than -2.5D)
usually doesn't cause amblyopia
unilateral high myopia (-6D)  sever
amblyopia visual loss.
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Amblyopia Due to bilateral high
refractive error (isometropia)
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isometropic amblyopia result from large,
approximately equal, uncorrected refractive
error in both eyes of a young child.
Hyperopia exceeding 5D & myopia excess of
10 D  risk bilateral amblyopia
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Meridonial amblyopia:
Uncorrected bilateral astigmatism in early
childhood may result in loss of resolving
ability limited to chronically blurred
meridians.
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Deprivation Amblyopia
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It is usually caused by congenital or early
acquired media opacity.
This form of amblyopia is the least common
but most damaging and difficult to treat.
In bilateral cases acuity can be 20/200 or
worse.
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In children younger than 6 years, dense
congenital cataract that occupy the central 3
mm. or more of the lens must be considered
capable of causing sever amblyopia.
Similar lens opacities acquired after 6 years
are generally less harmful.
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Small polar cataracts & lamellar cataracts
may cause mild to moderate amblyopia or
may have no effect on visual development.
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Occlusion amblyopia is a form of deprivation
caused by excessive therapeutic patching.
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Diagnosis
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Characteristics of vision alone cannot be used
to reliably differentiate amblyopia from other
form of visual loss.
The crowding phenomenon is typical for
amblyopia but not uniformly demonstrable.
Afferent pupillary defect are Characteristic of
optic nerve disease but occasiinally appear to
be present with amblyopia
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Multiple assessment using a variety of tests or
performed on different occasions are
sometime required to make a final judgment
concerning the presence and severity of
amblyopia.
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Binocular fixation pattern:
It is a test for estimating the relative level of
vision in the two eyes for children with
strabismus who are under the age of about 3.
This test is quite sensitive for detecting
amblyopia but results can be falsely positive.
Showing a strong preference when vision is
equal or nearly equal in the two eyes,
particularly with small angle strabismic
deviations.
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The modified Snellen technique directly
measures acuity in children 3-6 years old.
Often, however, only isolated letters can be
used, which may lead to under estimated
amblyopia visual loss.
Croding bar may help alleviate this problem.
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E O
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Crowding bar, or contour interaction bars, allow the
examinator to test the crowing phenomenon with
isolated optotype. Bar surrounding the optotype
mimic the full of optotype to the amblyopia child.
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Treatment
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Treatment of amblyopia involves the
following steps:
Eliminating (if possible) any obstacle to
vision such as a cataract
Correcting refractive error
Forcing use of the poorer eye by limiting use
of the better eye.
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Cataract removal
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Cataracts capable of producing amblyopia require
surgery without unnecessary delay.
Removal of significant congenital lens opacities
during the first 2-3 months of life is necessary for
optimal recovery of vision.
In symmetrical bilateral cases, the interval between
operations on the first and second eyes should be no
more than 1 week.
Acutely developing severe traumatic cataracts in
children younger than 6 years should be removed
within a few weeks of injury, if possible.
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Refractive correction
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In generally, optical prescription for
amblyopic eyes should correct the full
refractive error as determined with
cyclopagic.
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Occlusion and optical degradation
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Full time occlusion of the sound eye:
Defined as occlusion for all or all but one waking
hour.
It is the most powerful means of treating of
amblyopia by enforced use of the defective eye.
The patch can either be left in place at night or
removed at bedtime.
Spectacle-mounted occluser or special opaque
contact lenses can be used as an alternative to fulltime patching if skin irritation or poor adhesion
proves to be a significant problem
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Full time patching should generally be used
only when constant strabismus eliminates any
possibility of useful binocular vision because
 full time patching runs a small risk of
perturbing binocularity.
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Part-time occlusion:
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Defined as occlusion for 1-6 hours per day.
The children undergoing part time occlusion
should be kept as visually active as possible
when the patch is in place.
Compliance with occlusion therapy for
amblyopia declines with increasing age.
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Penalization:
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A cycloplegic agent (usually atropine 1% or
homatropine ) once daily to the better eye
This form of treatment has recently been
demonstrated to be as effective as patching
for mild to moderate amblyopia.
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E.B.M.
Evidence Based Medicine
Prospective, randomised
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PEDIG, MOTAS & COCHRANE
Eminence Based
Medicine
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Hopkins: weekend atropine
Scott [Iowa]: only full time
PEDIG
P
E
 Diatric ophthalmology
 Investigator
 Group
North American Community
based Ophthalmology and
optometry
MOTAS
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Monitored
Occlusion
Treatment of
Amblyopia
Study
England
Alistair Fielder
PEDIG:
Amblyopia 6/30 - 6/120
6 h/d vs. all [or all -1] waking hours
 Ages 3-7
 Can do reliable HOTV
 1h/d near activity
4mo: 4+ line improvement both groups
Age / severity of amblyopia NOT relevant to
outcome!
PEDIG:
Amblyopia 6/12- 6/24
2h vs. 6h/d opaque
occluder
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Ages 3-7
Can do reliable HOTV
1h/d near activity
4mo: same 2.4 line
improvement
Age / severity of amblyopia NOT
relevant to outcome!
PEDIG:
Amblyopia 6/12 - 6/24
Daily atropine vs. patch 6h/d
 6mo: no difference
 Patch: faster response
 2y: amblyopic eye 1.8 lines
worse in each group
 Improvement @ 2y: 3.6 vs. 3.7
lines
PEDIG:
Recurrence of amblyopia after stopping
treatment
≥ 3 lines acuity improvement
 25%: ≥ 2 lines loss @
12mo
 42% after stopping 6h/d
 14% if 6h/d tapered to
2h/d before stopping
MOTAS investigators:
Recurrence of amblyopia after stopping
treatment
Factors affecting the stability
of visual function following
cessation of occlusion
therapy for amblyopia.
Graefe 6/2007
Tacagni DJ, … Fielder AR
MOTAS investigators:
Recurrence of amblyopia after stopping treatment
1 y follow-up from treatment cessation:
children with "mixed" amblyopia
(both anisometropia and
strabismus) had significantly
(p=0.03) greater deterioration in VA
(0.11+/-0.11 log units) than children
with only anisometropia (0.02+/-0.08
log units) or only strabismus (0.05+/0.10 log units).
PEDIG:
Amblyopia 6/12 - 6/24
Daily vs. weekend
atropine
 Same results
 Daily slightly easier to do
 1/80: occlusion amblyopia
PEDIG:
Amblyopia 6/12 - 6/120 in 7-17yo
Glasses vs. glasses plus
 7-12: plus = patch 2-6h/d & daily
atropine
 Acuity improves by ≥ 2 lines
 13-17: plus = patch 2-6h/d
 Some have improved acuity
 12mo later: 20% have regressed
PEDIG:
Glasses alone
6/12 to 6/75
 27% cured
 Another 50% ≥ 2 lines better
 Took up to 7 mo
MOTAS
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GLASSES ALONE
‘REFRACTIVE ADAPTATION’
VA in 65 newly diagnosed children
with difft causes of amblyopia at 6w
intervals for 18w
VA improved significantly (p,0.001)
from 0.67 to 0.43 logMAR: a mean
improvement of 0.24 independent of
amblyopia type (p = 0.29) and age (p =
0.38)
Br J Ophthalmol 2004;88:1552-1556.
MOTAS
REFRACTIVE ADAPTATION
FOLLOWED BY OCCLUSION
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Prescribed dose 6h/d
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Compliance <50% [2.8h].
Only 10% used it ≥ 5.5 h/d
 0.1 [1 chart line] VA improvement per 120h
of occlusion
Total doses >200h:
 residual amblyopia <0.2 log
 >75% of deficit corrected
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IOVS 2004
MOTAS
REFRACTIVE ADAPTATION
FOLLOWED BY OCCLUSION
% of amblyopia deficit corrected
Type
Ref.
Adapt.
Occl.
Deficit
corrected
All
Aniso
Strab
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44
30
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42
50
78
86
80
Mixed
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50
77
MOTAS:
ELECTRONIC PATCH #1
18w of glasses, then patch
prescribed 6h , 12h/d
 6h/d: received 4.2 [± 0.5]
h/d
 12h/d: received 6.2 [± 1.1]
h/d
 p=0.06
 <3h/d: worse outcome
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MOTAS:
ELECTRONIC PATCH #2
6h/d prescribed
 Best acuity after 150 - 250
h
2 line gain:
 4y: needs 170h
 6y: needs 236h
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ELECTRONIC PATCH #3
Graefe 3/2003 Simonsz HJ et al.
Compliance : % of electronically
registered time c.f. prescribed time.
Satisfactory acuity increase
 ratio between acuity of the amblyopic eye
and acuity of the good eye > 0.75
 acuity of the amblyopic eye > 0.5 on E or
Landolt-C, or
 3 LogMAR lines of increase in acuity.
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Results:
Graefe 3/2003 Simonsz HJ et al.
Measured compliance
 ~ 80% in 8/14 children with satisfactory
acuity increase
 34% in 6 children with unsatisfactory
acuity increase.
 Children with low acuity increase had
statistically significantly lower compliance
p=0.038
 ‘no pain, no gain’
PEDIG
studies with completed enrolment
Enrollment Completed - Follow Up A
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Observational study of different types of esotropia
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RCT comparing near vs. distance activities while patching for
amblyopia
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RCT comparing atropine vs atropine with reduced + for sound eye
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Atropine vs occlusion in 7-12 yr old
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NFL in amblyopia
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RCT of Progressivelenses vs single vision lenses on low myopia
with large accommodative lags and near esophoria in children
Complication of therapy
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Full time occlusion carries the greatest risk of this
complication and requires close monitoring, especially in the
younger child.
The first follow up visit after initial treatment should occur
within 1 week for an infant and after interval corresponding
to 1 week per year of age for the older child.
Part time occlusion & optical degradation methods allow for
less frequent observation but regular follow up is still critical
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The time required for completion of
treatment depends on the following:
Degree of amblyopia
Choice of therapeutic approach
Compliance with the prescribed regimen
age of the patient
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Unresponsiveness
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Complete or partial Unresponsiveness to treatment
occasionally affect younger children but must often
occurs in patients older than 5 years.
Primary therapy should generally be terminated if
there is a lock of demonstrable progress over 3-6
months with good compliance.
Refraction should be carefully rechecked and the
macula and optic nerve critically inspected for
subtle evidence of hypoplasia or other malformation
that might have been previously overlooked.
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Recurrence
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When amblyopia treatment is discontinued after fully
or partially successful completion, approximately half
of patients show some dgree of recurrence,
Maintenance therapy:
Patching for 1-3 hours per day
Optical penalization with spectacles
Pharmacologic penalization with atropine 1 or 2 day
per week.
This may require periodic monitoring until age 8-10.
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