This document discusses amblyopia, including its classification, pathophysiology, clinical characteristics, evaluation, and management. It defines amblyopia and outlines its prevalence. Amblyopia can be classified as functional or organic, and further divided into types such as strabismic, anisometropic, and stimulus deprivation amblyopia. Clinical signs may include reduced visual acuity, abnormal fixation, impaired stereopsis, and altered contrast sensitivity. Evaluation involves assessing visual acuity, fixation, binocularity, and refractive error. Management is focused on occlusion therapy to treat the amblyopic eye.

1. Amblyopia : Classification and
Occlusion Therapy
MODERATOR PRESENTERS
DR.SANJEEV BHATTARAI AAYUSH CHANDAN
AASTHA SUBEDI

2. PRESENTATION LAYOUT
Introduction
Pathophysiology
Classification & types
Clinical characteristics
Clinical evaluation & diagnosis
Management
Occlusion Therapy
References

3. Definition
Derived from Greek word (Amblyos : Dullness/Blunt ; Ops : Vision)
U/L or less commonly B/L reduction in BCVA that cannot be attributed
directly to the affect of any structural abnormality of the eye or the
posterior visual pathway
Main cause of decreased vision in childhood
Difference of >2 lines between 2 eyes

4. Prevalence
Variable
2.0-2.5% of general population
Preschool/school age children : 4.0-5.3%
Globally 1.0-5.0% (WHO)
In Nepal around 0.9-1.8%

5. Risk factors
4 times more prevalent in LBW & premature baby
6 times more prevalent in delayed milestone & CNS disorders
Smoking & use of Drugs & alcohol during pregnancy have been a/w
risk of amblyopia

6. Sensitive Period
The capacity of the visual system to develop amblyopia is limited by its
state of maturity
During immaturity of the visual system the retinocortical connections are
not firmly established and may be modified by the quantity or quality of
the visual input
This phase has been described as the sensitive, critical, or susceptible
period
 The human is most sensitive to environmental manipulation during the
first 2 years of life
The human critical period is over by approximately 7 to 9 years of age

7. Classification
Functional amblyopia Organic amblyopia
Reversible Irreversible
Refers to obligatory psychical
suppression of the retinal image
Refers to partial loss of vision caused
by undetectable organic lesions in the
eye or in the visual pathway
Can be : Strabismic , Ametropic ,
Anisometropic , Meridional , Stimulus
Deprivation
Can be : Nutritional , Toxic , d/t Retinal
diseases , Idiopathic
Usually in Childhood Can cause VA defect at any age

8. Amblyopia of Arrest vs Extinction
Given by Chavasse
Amblyopia of Arrest caused by interference with the fixation reflex
that begins before 6 months of age i.e. during critical period of
development
Amblyopia of extinction resulting from suppression of an already
existing visual acuity (possible in children upto 6 years of age)

9. Pathophysiology
Amblyogenic factors
Role of Retina
Active cortical Inhibition

10. Amblyogenic factors
Visual
deprivation
• Monocular(seen in
Strabismic,
Anisometropic, Stimulus
deprivation amblyopia)
• Binocular(Seen in B/L
Cataract, Ametropia &
B/L high refractive Error)
Light
deprivation
• Usually seen in Children
with U/L or B/L complete
cataract
Abnormal
Binocular
Interaction
• Produces profound
amblyopia d/t
competition amblyopia
• Seen in
Strabismic,anisometropic
& U/L stimulus
deprivation amblyopia

11. Role of Retina
Decreased sensitivity of foveal cones in amblyopia
Decreased inputs from rods & cones in the affected eye cause
certain neurophysioloic changes, transmitted to the CNS which
triggers amblyopia

12. Active Cortical Inhibition
A developmental defect of spatial visual processing occurring in the
visual pathway.
Poor transmission from the fovea, optic nerve to the Striate Cortex
of the affected eye.
LGB & Striate cortex develop abnormally.
Ganglion cells in foveal area are affected; Shrinkage of LGB Nucleus
& Striate cortical fibres in the amblyopic eye.
Loss of binocularly driven cells in LGB & Striate Cortex

15. Classification & types
Strabismic amblyopia
Stimulus deprivation or amblyopia of disuse
Anisometropic amblyopia
Meridional amblyopia
Isoametropic amblyopia
Amblyopia secondary to nystagmus
Idiopathic amblyopia
Organic amblyopia

16. Strabismic amblyopia
Most common form of amblyopia
Amblyopia is unilateral
Seen in unilateral constant squint who strongly favour
one eye for fixation
Will develop in 100% of pts with constant untreated
acquired esotropia under 3 years of age resulting in
marked decrease in VA within week(treatment of this
type of amblyopia following acquired esotropia
therefore becomes daytime emergency)
19.7% of congenital cases of esotropia if untreated

17. Caused by active inhibition within the retinocortical pathway of visual
input originating in the fovea of the deviating eye.
Far more often in esotropes than in exotropes because exotropia is often
intermittent at its onset
Also be related to the nasotemporal asymmetry of the retinocortical
projections. In esotropes the fovea of the deviating eye has to compete
with the strong temporal hemifield of the fellow eye . In exotropia the
fovea competes with the weaker contralateral nasal hemifield
a/k suppression amblyopia
Contd…

18. Stimulus deprivation amblyopia/Amblyopia
of disuse(Amblyopia Ex Anopsia)
Primary cause is d/t disuse/under stimulation of the retina.
Least common but most damaging.
Caused when visual axis is obstructed.

19. Conditions exists in
 -opacities of the ocular media s/a congenital or traumatic cataract,
corneal opacities , blepharospasm , surgical lid closure , or U/L
Complete ptosis
 - B/L ptosis is not amblyogenic because the pt maintains normal
VA with a chin elevation

20. Anisometropic Amblyopia
Abnormal binocular interaction caused by unequal fovea images in
the two eyes causes development of the anisometropic amblyopia.
Always U/L
D/t active inhibition of the fovea.
30% of the cases are a/w strabismus
With reduction in central VA , overall reduction of the contrast
sensitivity
2nd main cause of amblyopia.

22. The amount of anisometropia that can induce amblyopia varies a/c
to type of refractive error
Hypermetropic anisometropia is more amblyopic than myopic
anisometropia
However U/L high myopia (-6D or more) often results in severe
amblyopia.
Refractive error Amount of anisometropia
Hypermetropia 1-2D
Myopia 3D or more
Astigmatism >1.25D

23. Meridional Amblyopia
Amblyopia occurring in pts with uncorrected astigmatic refractive error
d/t selective visual deprivation for visual stimulation of certain spatial
orientation.
occurs when a child progresses through the critical period with one visual
meridian in sharper focus than the other.
One study showed that half of neonates manifest astigmatism of between
0.75 and 2.00 D
It is probably best to consider prescribing lenses for young, school-age
children if the astigmatism shows no signs of abating and is at least 2.00 D

24. Clinical highlight
Meridional amblyopia is seen commonly in clinical practice. Depending on the
meridian affected, certain optotypes can be especially difficult to resolve
In the case of simple myopic, with-the-rule astigmatism ,horizontal gratings are
out of focus. Consequently, a patient with meridional amblyopia secondary to
this refractive error may find it difficult to resolve optotypes such as E or F,
which have substantial horizontal components

25. Isoametropic amblyopia
B/L amblyopia occurring in children
with B/L uncorrected high refractive
error.
Results from the effect of blurred
retinal image alone.
 Hyperopia > +5D
 Myopia > -10D
 Astigmatism >2D-2.5D

26. Amblyopia secondary to nystagmus
B/L amblyopia may occur secondary to nystagmus
But difficult to ascertain whether nystagmus is the cause or effect
of reduced VA

27. Idiopathic Amblyopia
U/L amblyopia occurring in apparently normal pt. with a negative history
for strabismus & in the absence of other usual amblyogenic factors.
Such pts have foveal suppression & VA improves after patching of the
sound eye.
A/c to Von Norden ; occurs d/t some amblyogenic factors (s/a transient
anisometropia) which are present in infancy for a short period but
disappears with advancing age.
In support of this hypothesis are observations that clinically significant
astigmatism or anisometropia in infancy may disappear with advancing
age

28. Organic Amblyopia
Irreversible type which results from some pathological or anatomical
abnormalities of retina
 Retinal eye disease
-Toxoplasmosis chorioretinitis , Retinoblastoma , traumatic retinal lesion
Nutritional amblyopia
-occurs from nutrition deficiencies

29. Toxic amblyopia
-Vision loss d/t damage to the optic nerve fibrosis d/t effects of
exogenous or endogenous poisons
-Types :
Tobacco amblyopia
Ethyl alcohol amblyopia
Methyl alcohol amblyopia
Quinine amblyopia
Ethambutol amblyopia

30. Tobacco amblyopia
-Typically occurs in men in pipe smokers, heavy drinkers
Ethyl alcohol amblyopia
-Usually in a/w tobacco amblyopia
-May occur in non-smoker but heavy drinkers suffering from chronic
gastritis

31. Methyl alcohol amblyopia
-It is typically acute usually resulting in optic atrophy & permanent blindness
Quinine amblyopia
-May occur even with small doses of the drugs in susceptible individuals
Ethambutol amblyopia
-caused d/t anti-tubercular drugs

32. Clinical characteristics

33. Visual acuity
Two line difference between amblyopic & normal eye.
For B/L amblyopia VA should be less than 20/40 in each eye.
Recognition acuity is more affected than resolution acuity &
detection acuity.
Snellens acuity & grating acuity are affected equally in
anisometropic amblyopia whereas in strabismic amblyopia grating
acuity is affected to half the extent of snellens acuity(strabismic
amblyopia is under-estimated on grating test)

34. Stereoacuity
Presence of amblyopia can be detected by defective performance
on various stereograms
Two pencil test is a clinically useful test and can be applied even
when VA recording is unreliable or not possible
Can also be easured by titmus fly test, randomdot stereogram

35. Neutral density filter
NDF reduces overall luminance without inducing a color
change
Decreased luminance of the visual target results in
diminished central acuity in normal eyes
Decreased luminance of visual target has less of an effect on
amblyopic eyes because they are not using central acuity
It was found that neutral filters profoundly reduce vision in
eyes with organic amblyopia whereas vision of eyes with
functional amblyopia was not reduced & occasionally even
slightly improved

37. Pharmacological effects on Vision of
amblyopic eyes
Gallois found that the use of vasodilators improved vision of
amblyopic eyes.
 Duffy et al found that Bicuculline a ϒ-aminobutyric acid (GABA)
receptor blocker If injected intracisternally in animals, substances
involved in the maturation of the central nervous system delayed the
maturation time and therefore eliminated the occurrence of
amblyopia.

38. Crowding phenomenon/Spatial
interaction
Amblyopic pts exhibit better VA for single Optotypes than for letters
placed in a row .
Although not specific for amblyopia, it may be pronounced in amblyopic
eye compared to better eye.
Based on phenomenon of simultaneous masking
Use of spatial gratings (the mask) to interfere with the detection of a
stimulus composed of similar frequencies (the target). Since both
frequencies share the same spatial frequency channels, there is a
reduction in the visibility of the target gratings.

39. Single line acuity improves more than line acuity during treatment So it is
important to record both single & line visual acuity everytime as it is prognostic
indicator.
Vision testing with single optotype is likely to overestimate VA in pts with
amblyopia
More accurate assesment of monocular VA is obtained with the presentation of
line of optotypes or single optotype with crowding bars that surround the
optotype being identified

40. Fixation pattern
Bangerter’s classified fixation pattern in amblyopia as :
i.central fixation
ii.Eccentric fixation(nonfoveolar)
iii.No fixation
Eccentric fixation can be divided into:
a.parafoveolar(adjacent to foveolar reflex)
b.parafoveal(outside but close to foveal wall)
c.peripheral eccentric(somewhere between edges of fovea & disc)

43. Visual field
Monocular VF are usually recorded as normal in strabismic
amblyopia . Although there is obviously a relative defect in the fovea
it is difficult to demonstrate it on a target screen or goldmann
perimeter
This clearly differentiates strabismic amblyopia from organic
amblyopia in which a scotoma involving the fovea area can be
plotted

44. Localization of an object of regard
Localization of an object of regard is normal in patients having
amblyopia with central as well as eccentric fixation .
However ,in patients having amblyopia with eccentric viewing ,
localization of an object of regard is faulty.

45. Color vision
Often abnormal , esp. when the amblyopia is severe .
Could simply be a function of the eccentricity of fixation.

46. Pupillary Responses
An afferent pupillary defect of amblyopic eyes has been reported by
several authors(9% to 93%) (Dole´nek)
 On Pupillographic measurements on the eyes of amblyopic children
it was found that on average the pupil of the amblyopic eye was 0.5
mm larger than the pupil of the normal eye in the natural state and
0.3 mm larger in miosis induced by a light stimulus (Dole’nek &
Kru¨ger).

47. Dark Adaptation
The dark adaptation curves to colored test targets of 26 amblyopic
subjects were studied.
Their normal eyes were used as controls.
No defects were found in the group having foveal fixation, but
significant defects were uncovered in the group having eccentric
fixation
Dark Adaptation in Strabismic Amblyopia; The Use of Colored Filters Flynn J.T. · Glaser J.S. November 27, 2009

48. Critical Flicker Frequency
Elevation of the CFF in the macular region relative to peripheral
area.(Lohmann & Teraskeli)
Normal CFF values in amblyopic eyes.(Weekers et al)
No difference in foveal CFF of amblyopic eye and its fellow eye
CFF was significantly faster in amblyopic eye that fixated eccentrically
than in those with foveal fixation.(Jacobson et al)

49. Electrophysiology Recordings
ERG is essentially normal & EOG shows unsteadiness of fixation in
Amblyopia .
Reduction in amplitude & slightly prolonged Latency in found in VEP.

50. Contrast Sensitivity
Reduction in contrast sensitivity more for higher frequencies.
Improves during amblyopia therapy & useful to monitor the
progress.
Contrast threshold becomes normal in strabismic amblyopia when
luminance levels were reduced , while the deficit persists in
anisometropic amblyopia.

51. Clinical evaluation & Diagnosis
Thorough clinical history
Binocular red reflex test(Bruckner’s Test)
Binocularity/stereo acuity testing
Evaluation of visual acuity and fixation pattern
Binocular alignment and ocular motility
External examination
Pupillary examination
Thorough ocular examination including fundus examination.
 Cycloplegic Retinoscopy / Refraction
Neutral density filter and testing for crowding phenomenon

52. Prognostic Factors in Amblyopia
Positive factor Negative factor
functional organic
Central fixation Eccentric fixation
Random dot stereopsis No random dot stereopsis
Short duration Long duration
Young patient, motivated Older patient, un-motivated
Strabismic > Anisometropic myopia > Anisometropic hypermetropia
Stimulus deprivation > Organic
Degree of prognosis

53. Management of amblyopia
Vision screening programs should be done.
I-ARM test ( Inspection- Acuity, Red reflex & Motility)
Bruckner’s red reflex test is vital for screening.
• Cataract:- white reflex
• Retinoblastoma:- yellow-white reflex
• Anisometropia:- unequal red reflex
• Strabismus:- brighter red reflex
Prevention & Early detection Treatment of amblyopia

55. Treatment of Amblyopia
Goals
Monocular goals
 Eliminate eccentric
fixation
 Eliminate eccentric
localization
 Establish foveal
fixation
 Establish foveal
localization
 Improve visual acuity
Binocular goals
 Eliminate sensory
anomalies
 Improve sensorimotor
visual skills
 Stabilize binocular
vision in open space
VS

56. Strategies to treat amblyopia
Eliminate cause of visual deprivation & provision of clear retinal image in
amblyopic eye.
Correction of ocular dominance
Perceptual training
Recommended treatment should be based on:-
Patient’s age
Visual acuity
Compliance with previous treatment
Physical, social & psychological status

57. Media clearance (for clear retinal image)
Childhood cataract, severe congenital ptosis & corneal opacity
should be treated as early as possible to prevent stimulus
deprivation amblyopia.
Significant congenital cataract should be removed during 1st 2-3
month of life.
In symmetric bilateral cases , interval between operation should
not be more than 1-2 weeks.
Acutely developing severe traumatic cataract in child < 8-10 yrs
should be removed within few weeks of injury.

58. Correction of ocular dominance
 Occlusion therapy
 Penalization
 Active stimulation
 Pleoptics
 Pharmacologic manipulation
Choices of treatment of amblyopia are used alone or in combination
1. Passive Therapy
The patient experiences a change in visual stimulation without any conscious effort
i. Proper refractive correction
ii. Occlusion
iii. Penalization
iv. Pharmacological manipulation

59. II) Active Therapy
designed to improve visual performance by the patient’s
conscious involvement in a sequence of a specific, controlled
visual task that provide feedback
i. Pleoptics
ii. Near activities
iii. Active stimulation therapy using CAM vision stimulator
iv. Syntonic phototherapy
v. Role of perceptual learning
vi. Binocular stimulation
vii. Software-based active treatments
These therapies are briefly described below with occlusion therapy in detail

60. Occlusion therapy
Introduction
 Passive treatment
Occlusion of the sound eye is the most effective treatment for
amblyopia treatment by forcing the patient to use the amblyopic eye.
Mainstay of treatment since 18th century to till now.
Highly effective until 8 years of age.

61. Causes progressive changes in visual functioning.
Success rate 30-92%
 When fixation is central: simple & effective
 When fixation is eccentric: <7yrs central fixation recover
 Older the child harder to regain central fixation

62. Mode of action
Prevent fixating eye taking part in act of vision and removes inhibitory
stimulus that arises from stimulation from fixating eye (non-amblyopic eye)
Occlusion goals
• Differential diagnosis
• Improvement of amblyopia
• Elimination of suppression
• Awareness or elimination of diplopia
• Disruption of anomalous
correspondence.

63. Types of occlusion
Occlusion
Total or
Partial
Conventional
or Inverse
Full Time or
Part Time

64. Total VS Partial Occlusion
Total Partial (light transmission)
•All light is prevented from
entering eye
•Employed in amblyopic eyes
with acuity less than 6/24
•Occlusion using elastoplast, gauze
pad, tape, doynes rubber occluder
•Does not cut off the total light
entering eye
•Degrades the vision of normal
eye such that amblyopic eye
gets better vision and
preference
•Occlusion using cellophane,
transparent nail polish, or a
higher plus lens

65. Partial /translucent
occlusion
Total occlusion
Given in
nystagmus
Amblyopia
treatment

66. Conventional or Direct Inverse
•Occlusion of sound eye
•Foveal or unsteady eccentric
fixation is present in amblyopic
eye.
•Occlusion of amblyopic
eye so that eccentric
fixation becomes less fixed.
• Steady eccentric fixation
Conventional vs Inverse occlusion

67. Additional points
 Inverse occlusion is prescribed whenever occlusion is needed but
direct occlusion is intolerable to the patient.
Given only if the patient is strongly resistant to direct occlusion.
For example:- A strabismic patient with deep amblyopia may not be able
to perform needed visual tasks with amblyopic eye . So 1st inverse
occlusion is started & changed to direct occlusion once more central
fixation and improved visual acuity are obtained
Inverse occlusion is started first to introduce the hesitant patient to a
patching regime.

68. Full Time vs Part Time
Full time Part time (Intermittent)
Removed only while going to bed
at night i.e all waking hours.
Short time each day during close
work .commonly( 1-6 hrs/day)
Choice of initial Rx
Given for constant strabismic
amblyopes.(regardless of size of
deviation)
In relapses after Rx and also for
maintenance
Given for intermittent
strabismics or non strabismic
amblyopes

69. Some exceptions to general rule
Constant exotropic patients who change quickly to an intermittent strabismus
with therapy ,instead of full time occlusion may need only part time occlusion or
even no occlusion.
Some non strabismic amblyopes with dysfunctional binocular vision may need
minimal to no occlusion esp when amblyopia is treated actively with
simultaneous improvement of sensorimotor processing.(Cohen 1981 ; Pickwell
1976)
Intermittent strabismic or heterophoric patients with symptoms d/t inefficient
binocular vision may need full time occlusion rather part time to allay binocular
symptoms until BSV is improved. After recovery of symptoms, patching schedule
is changed to part time.

70. Contd..
In infants & toddlers< 2 yrs of age, d/t greatest plasticity in neural processing
system,to prevent occlusion amblyopia, maximum 2 hrs/day is given & passive
lens,prism therapy is given together with active therapy.
Occlusion in Intermittent Strabismus
Time of occlusion depends on patient’s level of sensorimotor skills.
Since constant occlusion may break down binocular skills only part time
occlusion is recommended.
When not wearing patch patient’s existing binocular skills can be reinforced
through passive therapy & sensory anomalies such as suppression can be
eliminated when wearing patch.

71. Contd.
In intermittent strabismics,part time occlusion
eliminate central or foveal suppression & treat shallow
amblyopia eye after binocularity is achieved.
Nonstrabismic anisometropes or intermittent
strabismics with deep amblyopia requires most hours
of part time general occlusion
Intermittent strabismics with good peripheral
sensorimotor fusion & shallow or no amblyopia
requires least hours of part time general occlusion.

72. Occlusion in Constant strabismus
Earlier, full time occlusion followed by a day of rest was advocated. This
allows constant strabismus to regress to anomalous strabismic visual
processing on free day.
Nowadays, full time occlusion is prescribed initially. When intermittency is
achieved in open space ,part-time occlusion is given allowing some
reinforcement of binocular skills in normal activities.

73. Points on Occlusion
The presence (or absence) of amblyopia and its fixation pattern determine
which eye to patch
The frequency of strabismus determines the amount of time that the eye is
patched
Alternate occlusion
When equal visual acuity is present in each eye, (e.g :- a constant alternate
esotropia) , full time occlusion is alternated daily between two eyes.
The purpose of full time occlusion for strabismics with no amblyopia is to
eliminate suppression and possibly disrupt anomalous correspondence.

74. Types of occluders
 Adhesive skin patches made of micropore (best method)
 Commercially available opticlude
 Spectacle occluder:- patched eye remains visible to observer ,diffuse light
enters occluded eye from unblocked sides around the frame.
Child may look from top of glasses.
Good cosmesis
 Contact lens occluder:- Opaque center on contact lens
Total blockage of form & light
Good cosmesis
 Bandage occluder:- Total blockage of form & light
Difficult to remove
Greater chances of occlusion amblyopia
Poor cosmesis

75. Contact lens
occluder
Bandage occluder
Patches
Micropore
Spectacle occluder

76.  Tie-on occluder:- Easily removed or flipped up
no skin problems as bandage
 Clip-on occluder:-Attached to spectacle lens
diffuse light enters as in spectacle occluders
 Occlusion lens:-Form recognition is reduced by lens induced optical blur
a/k/a penalization lens or fogging lens
 Occlusion filters:-for the treatment of suppression & amblyopia
decrease both light & form transmission
neutral density or red filters are placed before normal eye &
are increased in density until fixation is forced to non preferred eye

77. Tie-on occluder Clip-on occluder
Occlusion lens Occlusion filter

78. Field coverage
Depends on how much of the visual field to block
Either the visual stimulation is blocked to whole visual field (total occlusion)
or just to specific portions of the visual field (partial occlusion) (d/t presence
and frequency of strabismus in a specific gaze or distance)
Other consideration is whether to cover both peripheral and the central
retina or just the central retina of the deviating eye.

79. Terminology Indication Visual field coverage
Total Constant strabismus at all distances & gazes Full field
Half- patch Constant strabismus at one distance &
intermittent or heterophoria at other.
Distance or near
field
Sector patches Incomitant strabismus.(intermittent in one
field of gaze & constant in other)
• BSV remain in nonaffected &
nonoccluded field
• Anomalous sensory processing can be
disrupted or diplopia can be eliminated
in affected field
• Achieve goal of binocular therapy
sequence
Selected gazes
Field Coverage Occluders

80. Terminology Indication Visual field coverage
Binasal Constant Esotropia Nasal fields( temporal
retina)
Bitemporal Constant exotropia Temporal fields(nasal
retina)
• Bipatches block the visual stimulation to a specific retinal region of
nonfixating eye which under unoccluded conditions would receive
anomalous visual stimulation d/t turning of eye.
• Both trigger alternation in viewing to amblyopic eye, leading to improved
visual acuity or elimination of foveal suppression.
• Both are alternate to total occlusion.
• Bitemporal occlusion disturb panoramic vision. So, not much favoured.

81. Bitemporal occlusion
Binasal occlusion
Sector occlusion

82. Age of patient (in yrs) Period of occlusion
(days)
Direct vs
Inverse
Follow up after every
Up to 2 2 : 1 15 days
3 3 : 1 15 days
4 4 : 1 1 month
5 5 : 1 1 month
6 or older 6 : 1 1 month
A simplified schedule for initial occlusion therapy for amblyopia

83. How to go about Occlusion?
Compliance is the keyword of success. Motivation of child and parents is necessary.
First the near vision then distance vision starts improving.
Active vision exercises by amblyopic while non- amblyopic eye is occluded
Occlusion is continued till amblyopic eye has developed equal vision and equal
preference of fixation
May take 3-6 month
If there is no improvement, on three consecutive monthly follow ups then treatment is
stopped, reevaluation is done.
Incomplete response to occlusion tends to be associated with anisohypermetropia &
anisoastigmatism.

84.  Follow up-depending on age, severity of amblyopia and compliance-
 to look for VA, fixation pattern and occlusion amblyopia
 When to stop occlusion
- VA equals in both eyes
- Alternation of fixation (Repka 2008)
 When VA is stable patching may be decreased slowly
 Because amblyopia recurs in large no. of pts. maintenance therapy or tapering
of therapy should be strongly considered

85. Disadvantages of occlusion
Occlusion amblyopia
Psychological distress
Allergic skin rash
Cosmetically inacceptable
Strabismic diplopia
Deviation changes

86. Occlusion amblyopia
When normal or preferred eye is occluded, visual acuity may decrease &
occlusion amblyopia may occur in the occluded eye.
The younger the child ,faster is the acuity loss & become profound and
permanent.Esp:- full time occlusion when given to infant <2yrs (critical
developmental yrs)
Alternate patching is given to prevent this & shorter period of direct
occlusion for younger children
For the remedy of skin reactions d/t patch that is in contact with skin
, hypoallergenic patch (Opticlude) can be used.
Tincture benzoin may be applied to the skin before applying patch.
This forms a protective layer & increase adhesiveness.

87. Strabismic diplopia
Occurs d/t extended period of total occlusion without resolution of strabismus
esp in older patients & those with anomalous correspondence.
In pts <10 yrs, suppression may regain in few weeks after discontinuation of
occlusion even after experiencing diplopia for several months when occluder is
removed.
 d/t tendency of suppression to lessen with age
 Difficulty in achieving BSV in long duration strabismus

88. Deviation changes
Appears to be expected progression of strabismic syndrome such as
accommodative esotropia or essential esotropia.
Dissociated vertical deviation may appear or previously measured
primary vertical deviation may increase in size.
Exodeviations may increase in size with full time or part time occlusion
& later become stable.
Some esotropic deviations continue to increase in size( without
increase in hyperopia) with time & after months they stabilize at a given
angle.

89. Occlusion removal & Maintenance occlusion treatment
Occluder is not removed until comfortable ,efficient binocularity has been
obtained, and patient is capable of maintaining binocular vision in open space
without regressions.
Most errors are made in removing the occluder too soon. Regressions from
non strabismus to strabismus may occur in a relatively short time (1 to 3
months).esp. intermittent or constant strabismus
Once the vision has been equalized, the maintenance occlusion should be
continued till the amblyogenic , i.e up to at least 9 years of age.
Maintenance by occlusion is accomplished a part-time occlusion for 2-3
hours in a day with active vision exercises at home.

90. Treatment of Anisometropic Amblyopia

91. Treatment of Strabismic Amblyopia
Treatment options for strabismus
1.No treatment
2.Lens
3.Prism
4.Occlusion
5.Filters
6.Orthoptics
7.self-monitoring system
8.Medication
9.Surgery
10.Referrals

92. Amblyopia Treatment Study
Paediatric Eye Disease Investigator Group(PEDIG) is a collaborative
network dedicated to facilitating multicenter clinical research in
strabismus , amblyopia & other eye disorder that affect childrenn
 In the ATS,
1. mild to moderate amblyopia VA in the amblyopic eye of 6/24
or better;
2. severe amblyopia is VA in the amblyopic eye of 6/60 to 6/120

94. ATS Age of
child
Objective (to
compare)
Conclusion
3 7-17 Various treatment of
amblyopia
VA (6/12 to 6/120)
 Optical correction alone improves
VA in 1/4th of the pts.
7-12  2-6 hrs of patching with near
activities or atropine,VA improved
even if amblyopia has been
previously treated.
13-17 2-6 hrs of patching with near
activities ,VA improved even when
amblyopia has not been treated
previously.

95. ATS Age of child Objective (to compare) Conclusion
4 <7 yrs Daily vs weekend atropine
for strabismic or
anisometropic amblyopes
with VA 6/12 to 6/24
Daily = weekend
5 3-7 yrs Effectiveness of refractive
correction alone for
untreated anisometropic
amblyopia
Resolution occurs in at least
1/3rd of pts.
VA improved by >= 2 lines in
77%
5(2) 3-7 yrs 2hrs patching ( with near
activity) vs spectacle
alone in mod to severe
amblyopes
Patching >> spectacle
correction alone

96. ATS Age of child Objective (To compare) Conclusion
13 3-7 yrs. VA improvement in
children with strabismic
& combined strabismic-
anisometropic
amblyopia treated with
optical correction alone
Treatment effect was
greater for strabismic
than combined
mechanism amblyopia.
15 3-8 yrs. Increasing patching for
2-6 hrs. with VA(20/50-
20/400)
When VA stops improving
with 2 hrs. of patching,
increasing patching to 6
hrs. result in VA
improvement.

97. Practical examples of occlusion
Three factors govern occlusion schedule
Age
Refractive error
Visual Acuity
There is no hard & fast rule to
prescribe occlusion schedule.

98. Some points
Direct occlusion is given age hrs/day. i.e 4yrs:- 4hrs/day
>6 yrs :- 6hrs/day
VA is plays most important rule. No. of lines difference in VA:-
same ratio in direct occlusion .eg:- 3 lines difference= 3:1 ratio
When lens are prescribed for the first time , it is advisable to
wait for 4 weeks & reassess frequency of strabismus before
determing appropriate occlusion plan.

99. Age RE LE Ratio (RE:LE) Time /day
4 yrs 6/6 with
plano
6/18 with
+2.00 Dsph
3:1 4hrs/day
5 yrs 6/60 with
+5.00 Dsph
6/18 with
+2.00 Dsph
1:3 5hrs/day
7 yrs 6/6 with
plano
6/60 with
+3.00 Dsph
6:1 6hrs/day

100. Age RE LE Ratio (RE:LE) Time (hrs/day)
4 yrs 6/9 with +1.00
Dsph
6/12 with
+2.00 Dsph
2:1 4 hrs/day
8 yrs 6/18 with
+3.00 Dsph
6/18 with
+3.00 Dsph
1:1 6 hrs/day
6 yrs 6/18 with
+1.50/-
3.00*180
6/60 with
+1.50/-
5.00*180
3:1 6hrs/day

101. Age RE LE Ratio (RE:LE) Time
(hrs/day)
7 yrs 6/6 with
plano
5/60 with
+6.00 Dsph
6: free 6hrs/day
5 yrs 6/18 with
+3.00 Dsph
5/60 with
+7.00 Dsph
< 4:1
(3:1) given
5 hrs/day
(close f/ups)
2 yrs Only LE is
patched
initially.
2hrs/day.
(close f/ups)RE constant esotropia.
VA Couldn’t be assessed.

102. Refractive error correction
• Improves VA in 25-33% of patients with anisometropic amblyopia and also in
strabismic amblyopia
• Cycloplegic refraction followed by adequate optical correction
• ATS 5 concluded that amblyopia improved with optical correction in 77% and
resolved in 27%
• Chen et al (AJO 2007) concluded that penalization and occlusion is required only
if the child doesn’t improve with glasses for four months
• In general eye glasses are well tolerated by children especially when there is
improvement in visual function.

103. When to prescribe??

104. Other Treatment modalities
Besides occlusion therapy;
 Penalization
 Pleoptics
Active vision therapy using CAM vision stimulator
 Pharmacological manipulation
Software based active treatments
plays important role in amblyopia treatment.

105. Summary
The clinical features and laboratory findings in eyes with amblyopia permit certain
conclusions for understanding the nature of the processes underlying amblyopia and
its treatment.
 Decreased visual acuity, although clinically the most tangible defect, is but one of
the many disturbances associated with amblyopia regardless of its etiology
 Basic amblyogenic mechanisms are the same even though their contribution to
each type of amblyopia varies
Most of the active therapy methods have good results when used together with
patching therapy
Early detection & Screening programs should be done to prevent amblyopia
Amblyopia is still an unsolved problem, the best modality of treatment is still to be
explored in future

106. REFERENCES
Binocular Vision & Ocular Motility ; Gunter K. Von Noorden
Theory and practice of Squint & Orthoptics ; A.K Khurana
Management of strabismus & Amblyopia ; John A. pratt-Johnson
Clinical management of Strabismus ; Elizabeth E. Caloroso
Previous Presentations
Internet