Amblyopia: definitions, screening, clinical evaluation and management. This ppt outlines the current management protocols as per studies.

1. Dr. Obaidur Rehman
Junior Resident
Government Medical College & Hospital
Chandigarh

2. Definition and types
 Amblys = dull , ops = eye
 Decrease in visual acuity in one eye when caused by abnormal
binocular interaction or occurring in one/both eyes as a result of
patterned vision deprivation during immaturity, for which no cause
can be detected during physical examination of the eyes and which
is reversible by therapeutic measures at appropriate time
 Clinically, defined as difference in BCVA between the two eyes of
atleast 0.20 logMAR or 2 lines on Snellen chart
Noorden GK, Campos EC. Binocular Vision and Ocular Motility, 6th edition

3. • Anisometropic amblyopia – difference in refractive error between
the eyes
• Strabismic amblyopia(most common)– abnormal binocular
interaction due to suppression of deviated eye
• Stimulus deprivation amblyopia – unilateral/bilateral vision
deprivation
• Bilateral ametropic amblyopia – high symmetrical refractive
error, usually hypermetropia
• Meridonial amblyopia – blurred image in one meridian due to
uncorrected astigmatism
Bowling B. Kanski’s Clinical Ophthalmology 8th edition.

4. Epidemiology
 1-5% population affected in developed countries
 In India, 1-4% of children affected
 In an Indian study in school children, incidence found to be 1%.
Higher in rural(0.7%) than urban(0.5%)
Weber JL, Wood J. Amblyopia: Prevalence, Natural History, Functional Effects and Treatment.
Clinical and Experimental Optometry. 2005; 88: 365-75.
Vijaylakshmi P, Panadikar R. Classification of amblyopia. Strabisscope 1996; 3: 6-7.
BS Goel. Strategy for early detection of amblyopia. Strabismology and Pediatric Ophthalmology
1999; 5: 9-11.

5. Pathophysiology
 Normal Retino-geniculo-cortical pathway
 Critical period
3 periods in development of visual acuity and ocular dominance
i) Development of acuity: birth to 3-5 yrs
ii) Period during which deprivation causes amblyopia: birth to 7-8 yrs
iii) Period during which recovery can occur: time of deprivation to
teenage life
 Time of functional architecture development and maturation of visual
cortex is the ‘critical period’.
 Imbalance/disruption in this period leads to alteration in neuronal
signals to visual input.

6. Retinal changes
 Development of retinal cones depends on visual experience and
maturation continues till adulthood
 Amblyopigenic factors hinder in maturation of cones and reduced
sensitivity of foveal cones has been noted in Amblyopes
 Reduced bioelectric activity in retina, as shown using
Electroretinogram studies by Slyshalova, has been noted in
Amblyopes
Stellwagen D, Shatz CJ. An instructive role for retinal waves in the development of retinogeniculate
connectivity. Neuron 2002: 357-367.
Slyshalova NN, Shamshinova AM. Retinal bioelectrical activity in amblyopia. Europe PMC 2008.
124:32-36

7. Cortical changes
 Hubel and Wiesel demonstrated that the axons carrying visual stimuli
from the 2 eyes form ocular dominance columns(ODC) in the primary
visual cortex, in which inputs from the 2 eyes alternate equally.
 Axonal arborization, forming multiple connections occurs in Lateral
Geniculate Nucleus and Cortex.
 Cortical circuit is immature in postnatal life and ODCs amenable to
alteration.
 Decreased stimuli from one eye during critical period leads to
narrowing of ODCs in this eye and expansion in the fellow eye
Le Vay S, Wiesel TN, Hubel DH. The development of ocular dominance columns in normal and visually
deprived monkeys. J Comp Neurol 1980;191:1-51.

8. Amblyopigenic factors/abnormal binocular
interaction cause blurred image on the
affected Retina
Active inhibition of blurred image
Cortical spatial changes in ODCs.
Reduced connections in LGN and Cortex
Decreased visual acuity in affected eye

9. Clinical evaluation
 Thorough clinical history- current age
- age when low vision noted
- duration
- deviation noted or not, constant/intermittent
- white reflex or any other abnormailty noted
- family h/o low vision/squinting
- prior treatment received
 Thorough clinical examination, including Acuity, pupillary reactions,
extraocular movements, anterior segment and posterior segment
examination.

10. Clinical signs
 Deceased visual acuity
 Decreased stereoacuity
 Fixation preference
 Crowding phenomenon
 Deviation in strabismic amblyopia

11. Diagnosis & Ancillary testing
 Key to successful treatment: Early detection
 Screening at young age: Cost effective and clinically effective
American Academy of Ophthalmology recommends first screening by
the age of 3 years and thereafter every 2 years
 Ideal treatment window: first decade of life
 Regular screening programs in schools have aided in early detection
of low vision in children and timely referrals to hospitals

12. Visual Acuity
 Atleast a difference of 2 lines between the amblyopic eye and normal
eye on Snellen chart
 For Bilateral disease: VA 6/12 or less in each eye
 Pre-verbal children
- Fixation and following: Using bright attention grabbing objects
- Comparison of two eyes: Reveals unilateral preference
Child strongly objects to occlusion of normal eye
- Fixation behaviour: Look for centration/steadiness/maintainence
- Preferential looking: Infants prefer patterns rather than simple
stimulus. Teller cards(gratings) or Cardiff cards used.

13.  Verbal children
- Preferable to test at 4 meters distance than 6 meters (better
compliance)
- 2-3 years: Picture charts or crowded Kay chart or matching of
optotypes charts
- Older children: Crowded letter tests used

14. Crowding phenomenon
 Also called separation difficulty, it is the inability to discriminate
optotypes that are crowded closely
 Amblyopes can discriminate optotypes when presented singly
against a uniform background(angular acuity/single E acuity) rather
than when presented in a row(line acuity/Snellen acuity)
 Contour interaction and lateral inhibition suggested as underlying
mechanism
 Single optotype acuity improves more than line acuity with treatment
Thus, imperative to evaluate both
Noorden GK, Campos EC. Binocular Vision and Ocular
Motility, 6th edition

15. Stereopsis
 Measured in seconds of arc
 Normal spatial resolution = 1 minute
Normal stereoacuity = 60 seconds
 Lower value: better
 Titmus test: 3-D polarized vectograph with 2 plates, viewed with
polarized spectacles. Right side has a large fly, Left side has series
of circles and animals. Performed at 40 cm distance.
- Fly: Gross stereopsis(3000 seconds), for younger children. Ask to
hold wings between finger and thumb
- Circles: Graded series 800 to 40 sec of arc. One circle stands out
from the rest
- Animals: 400 to 100 sec of arcs. One animal stands out

17.  TNO test: Radomly distributed red & green dots viewed with red-green
spectacles. In different plates, different shapes formed. Measures 480
to 15 seconds of arc.
 Lang test: Targets seen with one eye at a time through built-in
cylindrical lens. Plates have dots that create disparity and a shape is
seen. Does not require special spectacles.

18. Sensory Anomaly testing
 Worth 4 dot test: Patient wears red lens in front of right eye and
green in front of left eye.
Asked to view box with 4 lights: one white, one red, two green.
- Normal BSV: All 4 seen
- 2 reds seen: Left suppression
- 3 greens: Right suppression
- 2 red & 3 green: Diplopia
- Alternating red and green: Alternate suppression

19.  Bagolini striated glasses: Patient wears glasses with lens having
striations, that converge point source of light into a line.
The two lenses are placed at 45 and 135 degrees respectively, and
fixated on a focal light source.
- lines intersect at their centres in X pattern: Normal BSV
- lines seen but no crossing: diplopia
- only one streak seen: supression
- small gap in one of the streaks: suppression scotoma

20. Deviation measurement
 Hirschberg test: Rough objective estimate of manifest strabismus
Pen torch shone in patient’s eye at an arm’s length
Corneal reflection in deviated eye is decentred, opposite to direction
of squint. 1mm deviation ~ 7 degrees(15 dioptres)
- at temporal border of pupil ~ 15 degrees
- at limbus ~ 45 degrees
 Krimsky test: Prisms placed in front of fixating eye until corneal
reflections symmetrical
 Prism reflection test: Prisms placed in front of deviated eye until
corneal reflections symmetrical

21.  Cover-uncover test
Cover test: detect heterotropia.
- Patient looks straight, examiner covers fixing eye and
notices movement of deviated eye
- No movement: Orthotropia/heterotropia of fixing eye
- Movement and Fixation of deviated eye: Heterotropia in
deviated eye
- Downward movement: Hypertropia
- Upward movement: Hypotropia
Uncover test: detect heterophoria
- Patient looks straight, examiner covers the eye for 2-3
seconds and notes movement after uncovering
- No movement: Orthophoria
- Adduction: Exophoria
- Abduction: Esophoria
- Upward/downward: Vertical phoria

22.  Alternate cover test: Induces dissociation to reveal deviation on
fusion disruption
- One eye covered for few seconds, occluder then shifted to other
eye.
- Back and forth shifting few times
- Decompensation to manifest deviation seen in a patient with poor
control.
 Prism cover test: Measure angle of deviation in near/distance fixation
- prism bar with prisms of progressive strength used
- prism placed in front of the eye, with base opposite to direction of
deviation
- amplitude of re-fixation noted with increasing strength
- strength of prisms increased till no movement seen

23. Refraction
 Cycloplegic refraction should be carried out in all children
 Prevents underestimation of the refractive error and better
visualization of retinoscopic reflex
 Cyclopentolate: 0.5% for infants, 1% for older children
1 drop, repeated after 5 minutes
Retinoscopy performed 45 min after first drop
 Atropine ointment: 0.5% for infants, 1% for older
Preferred in children <5 years
Applied twice daily, for 3 days before refraction

24. Treatment
 Early diagnosis and initiation of therapy is the key.
A study by Pediatric Eye Disease Investigator Group (PEDIG) on
treatment of moderate strabismic and/or anisometropic amblyopia
showed that the visual acuity of the amblyopic eye improved to 20/30
or better 6 months after initiating treatment in 75% children under 7
years of age
 Principles
- Removal of cause of amblyopia
- Correction of refractive error
- Promotion of use of amblyopic eye over fellow eye

25.  Cataract removal
- Removal of congenital cataracts within 4-6 weeks of life
- In B/L disease, interval between both eyes should be 1-2 weeks
- Significant traumatic cataract should be removed withing few weeks
 Refractive error correction
- initial treatment of choice
- cycloplegic refraction f/b adequate correction
- vision improvement in 1/3rd patients observed in Amblyopia
Treatment Study
- full correction of astigmatism, myopia and anisometropia
- undercorrection of hypermetropia by no more than +1.50DS

26.  PEDIG has performed extensive research on amblyopia in the
Amblyopia Treatment Study(ATS)
 Optimal refractive correction with frequent follow ups should be tried
as first line of treatment
ATS 5 Studied effect of refractive corrcction alone in
anisometropic amblyopia. Total resolution noted
in 27% patients
ATS 7 Studied effect of refractive correction alone in
bilateral refractive amblyopia. 74% achieved
BCVA 20/25
ATS 13 Effect of refractive correction alone in strabismic
amblyopia. Full resolution in 32% patients noted
Pediatric Eye Disease Investigator Group. Optical Treatment of Strabismic and Combined
Strabismic-Anisometropic Amblyopia. Ophthalmology 2011

27. Recommended refractive correction in children
www.aao.org

28. Active treatment- Occlusion therapy
 Occlusion of the sound eye removes inhibitory stimulus, arising from
it’s visual stimulation
 Initiated in children who are not improving with refractive correction
alone
 Types of occluders - adhesive skin patches
- commercially available opticludes
- spectacle/contact lens occluder
 Constant motivation of child and parents needed
 Encourage active vision exercises

29.  ATS studies
 These studies showed that patching was an effective treatment for
treating amblyopia. Part time patching is the preferred modality.
 Optimal improvement occurs when BCVA is first stabilised with refractive
correction, then patching initiated
Pediatric Eye Disease Investigator Group. A randomized trial comparing Bangerter filters and
patching for treatment of moderate amblyopia in children. Ophthalmology 2010; 117: 998-
1004
ATS 2b Compared 2 hours vs 6 hours patching in moderate amblyopia.
At 4 months, BCVA improvement of 2.4 lines in both with better
compliance in 2 hour group
ATS 2a Compared 6 hour patching vs full time patching in severe
amblyopes. At 4 months, both groups had 4.8 lines BCVA
improvement with better compliance in 6 hours group
ATS 5 2 hours patching in mod. and severe amblyopia after BCVA
stabilisation with spectacles. 2.2 lines improvement seen in patching
group compared to control group

30.  PEDIG studies now recommend 2 hours patching in moderate
amblyopia(VA 20/40-20/100) and 6 hours patching in severe
amblyopia(VA 20/100-20/400)
 Follow up depends on age, severity and compliance
 If no improvement seen despite compliance, look for other causes
Pediatric Eye Disease Investigator Group. A randomized trial comparing Bangerter filters and patching
for treatment of moderate amblyopia in children. Ophthalmology 2010; 117: 998-1004

31. Kapoor S. Update on Diagnosis and Management of Amblyopia.

32. Penalisation
 Optically defocusing the better eye with therapeutic means
 Cycloplegia with atropine or using glass lens
 Indicated in - non compliant patients
- mild amblyopia
 Disadvantages - Systemic absorption of Atropine and side effects
- Occlusion amblyopia

33.  ATS study
 PEDIG studies have found atropinisation to be as effective as
patching
Pediatric Eye Disease Group. A randomized trial of atropine vs patching for treatment of amblyopia
in children. Arch Ophthalmol 2002. 120:268-78.
ATS 1 Studied 1% daily Atropine vs 6 hours patching in
mod amblyopia. At 2 yrs, 20/32 vision in 86%
patching and 83% atropine group
ATS 4 Daily atropine use compared to weekend only use.
Both groups improved by 2.3 lines
ATS 8 Compared refractive correction alone with
correction plus atropinisation. Treatment group
imrpoved to 2.8 lines vs 2.4 lines in control group

34. Surgery
 Stabismus surgery should always be performed after
adequate treatment for and reversal of amblyopia
 Refractive surgeries for refractive amblyopia in non-
compliant patients
- enhance binocular vision
- improve spectacle tolerance

35. Pharmacologic adjuncts
 Levodopa: Some investigators reported low levels of retinal
Dopamine in deprivation amblyopia
- a PEDIG trial with levodopa and 2 hours patching found no
significant gain in visual acuity
- another trial by Sofia et al, utilising 3 times more dosage than
PEDIG trial found significant vision gain at 1 year follow up
 Citicholine: Confers cholinergic and neuroprotective properties.
- earlier studies were promising
- no concrete evidence to support use
Sofi IA, Gupta SK, Bharti A, Tantry TG. Efficiency of the occlusion therapy with and without
levodopa-carbidopa in amblyopic children-A tertiary care centre experience. Int J Health Sci
2016;10:249-57.

36. Upcoming modalities
 Binocular visual stimulation: through the use of dichoptic glasses
while playing video games is the newest treatment regimen under
investigation
- patients wearing red-green 3D glasses asked to play games on
iPad
- amblyopic eye receives higher contrast than fellow eye
- as binocular function develops, contrast gradually reduced upto a
potential point where no difference in contrast is required

37.  PEDIG conducted a large-scale trial comparing the effectiveness of 1
hour/day, 7 days/week binocular game play to 2 hours/day patching in
children<13 and found no statistically significant difference between
the groups at 16 weeks.
Holmes JM, Manh VM, Lazar EL, et al. . Effect of a Binocular iPad Game vs Part-time
Patching in Children Aged 5 to 12 Years With Amblyopia: A Randomized Clinical Trial. JAMA
Ophthalmol 2016;134:1391–400.

38. AmbP iNet program for the treatment of amblyopia
 Can be assessed at http://www.visiontherapysolutions.net
 12 treatment programs, five days per week
 Designed to improve hand eye co‐ordination, visual acuity, crowding
effect and visual memory
 Improvement in acuity as well contras sensitivity seen
Avram E, Stanila A. Treating anisometric amblyopia with HTS Amblyopia iNet Software--preliminary results.
Oftalmologia 2013; 57:32-7

39. Interactive binocular treatment (I-BiT) system
 Dichoptic stimuli presented via virtual reality game play or movie
watching
 Shutter glasses used, where the glasses lighten and darken in
synchrony with the monitor, allowing an enriched image to be
presented to the amblyopic eye only
 Treatment well tolerated and imrovement in visual acuity seen in
studies
Herbison N, MacKeith D , Vivian A , et al . Randomised controlled trial of video clips and interactive games to
improve vision in children with amblyopia using the I-BiT system. Br J Ophthalmol 2016;100:1511–6.

40.  Liquid crystal display eyeglasses: eyeglasses alternate between a
clear and opaque lens before the fellow eye
- an electronic shutter controlled by a pre-programmed microchip
- improvement in near and distance visual acuity noted
- compliance found to be better than patching
Spierer, A., Raz, J., BenEzra, O., Herzog, R., Cohen, E., Karshai, I., & BenEzra, D. (2010).
Treating Amblyopia with Liquid Crystal Glasses: A Pilot Study. Investigative Opthalmology & Visual Science,
51(7), 3395. doi:10.1167/iovs.09-4568

41. Take home message
 Amblyopia is a common childhood problem
With early screening and treatment, economic as well as social
burden of the disease can be reduced
 Appropriate and early therapy can help achieve good visual
outcomes
 Motivated , compliant child and parents are an ally to the therapist in
treatment
 Goal of therapy should also include attainment of good binocular
function, apart from visual acuity

42. Thank you