Title: Amblyopia
1Amblyopia
2- 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.
3Resulting from one of following
- Strabismus - DEVIATION
- Anisometropia or high bilateral refractive error
(Isoametropia) - DEFOCUS - Visual deprivation - DEPRIVATION
4- 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
5- 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.
6Neurophysiology
- Cells of the primary visual cortex can completely
lose their innate ability or show significant
functional deficiencies - Abnormalities also occur in neurons in the
lateral geniculate body - Evidence concerning involvement at the retinal
level remains inconclusive
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10Classification
- Strabismus Amblyopia Deviation
- Anisometropia Amblyopia Defocuss
- Amblyopia Due to bilateral high refractive error
(isometropic) Defocuss - Deprivation Amblyopia Deviation
11Strabismus Amblyopia
- 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.
12Anisometropia Amblyopia
- 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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14- 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.
15Amblyopia Due to bilateral high refractive error
(isometropia)
- 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
16- Meridonial amblyopia
- Uncorrected bilateral astigmatism in early
childhood may result in loss of resolving ability
limited to chronically blurred meridians.
17Deprivation Amblyopia
- 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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19- 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.
20- Small polar cataracts lamellar cataracts may
cause mild to moderate amblyopia or may have no
effect on visual development. - Occlusion amblyopia is a form of deprivation
caused by excessive therapeutic patching.
21Diagnosis
- 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
22- 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.
23- 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.
24- 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.
25- 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.
26Treatment
- 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.
27Cataract removal
- 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.
28Refractive correction
- In generally, optical prescription for amblyopic
eyes should correct the full refractive error as
determined with cyclopagic.
29Occlusion and optical degradation
- 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
full-time patching if skin irritation or poor
adhesion proves to be a significant problem
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31- 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.
32- Part-time occlusion
- 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.
33- Penalization
- 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.
34E.B.M.
- Evidence Based Medicine
- Prospective, randomised
- PEDIG, MOTAS COCHRANE
- Eminence Based Medicine
- Hopkins weekend atropine
- Scott Iowa only full time
35PEDIG
- P
- E
- Diatric ophthalmology
- Investigator
- Group
- North American Community based Ophthalmology
and optometry
36MOTAS
- Monitored
- Occlusion
- Treatment of
- Amblyopia
- Study
- England Alistair Fielder
37PEDIG 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!
38PEDIGAmblyopia 6/12- 6/24
- 2h vs. 6h/d opaque occluder
- 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!
39PEDIGAmblyopia 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 _at_ 2y 3.6 vs. 3.7 lines
40PEDIGRecurrence of amblyopia after stopping
treatment
- 3 lines acuity improvement
- 25 2 lines loss _at_ 12mo
- 42 after stopping 6h/d
- 14 if 6h/d tapered to 2h/d before stopping
41MOTAS investigatorsRecurrence 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
42MOTAS investigatorsRecurrence of amblyopia
after stopping treatment
- 1 y follow-up from treatment cessation children
with "mixed" amblyopia (both anisometropia and
strabismus) had significantly (p0.03) 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).
43PEDIGAmblyopia 6/12 - 6/24
- Daily vs. weekend atropine
- Same results
- Daily slightly easier to do
- 1/80 occlusion amblyopia
44PEDIGAmblyopia 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
45PEDIGGlasses alone
- 6/12 to 6/75
- 27 cured
- Another 50 2 lines better
- Took up to 7 mo
46MOTASGLASSES ALONEREFRACTIVE 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 2004881552-1556.
47MOTASREFRACTIVE ADAPTATION FOLLOWED BY OCCLUSION
- Prescribed dose 6h/d
- Compliance lt50 2.8h.
- Only 10 used it 5.5 h/d
- 0.1 1 chart line VA improvement per 120h of
occlusion - Total doses gt200h
- residual amblyopia lt0.2 log
- gt75 of deficit corrected
- IOVS 2004
48MOTASREFRACTIVE ADAPTATION FOLLOWED BY OCCLUSION
- of amblyopia deficit corrected
Type Ref. Adapt. Occl. Deficit corrected
All 32 47 78
Aniso 44 42 86
Strab 30 50 80
Mixed 27 50 77
49MOTASELECTRONIC 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
- p0.06
- lt3h/d worse outcome
50MOTASELECTRONIC PATCH 2
- 6h/d prescribed
- Best acuity after 150 - 250 h
- 2 line gain
- 4y needs 170h
- 6y needs 236h
51ELECTRONIC 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 gt 0.75 - acuity of the amblyopic eye gt 0.5 on E or
Landolt-C, or - 3 LogMAR lines of increase in acuity.
52Results 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
p0.038 - no pain, no gain
53PEDIGstudies with completed enrolment
- Enrollment Completed - Follow Up A
- Observational study of different types of
esotropia - RCT comparing near vs. distance activities while
patching for amblyopia - RCT comparing atropine vs atropine with reduced
for sound eye - Atropine vs occlusion in 7-12 yr old
- NFL in amblyopia
- RCT of Progressivelenses vs single vision lenses
on low myopia with large accommodative lags and
near esophoria in children
54Complication of therapy
- 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
55- 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
56Unresponsiveness
- 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.
57Recurrence
- 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.