amblyopia pathology and types

1. AMBLYOPIA

2. Definition
Amblyopia is a unilateral / bilateral(occasionally), reduction in best-corrected
visual acuity -
• In an other wise healthy eye
• In an eye with structural abnormality, where reduction in vision cannot be
solely attributed to the abnormality.

3. Prevalence
• Developing countries- 1.8% - 5.3%
• Proportion of bilateral amblyopia – 5 to 41%
• In presence of strabismus, amblyopia increase to 2.7-18 times

4. Pathophysiology

8. Amblyopia is Characterized by Changes in
Cortical Architecture and Function
Normal
Monocular Deprivation

9. Inhibitory Tone in the Visual Cortex
• Cortical inhibition levels cross two levels of thresholds during visual
development
• GABA is an important inhibitory neurotransmitter in human cerebral cortex
CP begins CP ends

10. Whom to treat?
• Early research- critical period- 8-9 years.
• Recent research- improvement of VA in young adolescents and adults
Conclusion- neural plasticity may be preset longer than previously reported
Treatment should be offered to adults who have not been treated previously or
previous failed treatment

11. Amblyogenic factors
• Visual deprivation as occurs in anisometropia(form sense)
• Light deprivation as in congenital cataract and ptosis(light sense)
• Abnormal binocular interaction as in strabismus.

12. Classification
Classification Latrality Causative factor
Strabismic Unilateral Childhood onsent manifest
strabismus
Anisometropic Unilateral Significant intraocular difference
in spherical refractive error
Meridional Unilateral Significant intraocular difference
in astigmatic refractive error
Stimulus deprivation Unilateral/bilateral Blockage of light and/or form
stimulus in early life.(congenital
cataract or ptosis)
Ametropic Bilateral Uncorrected bilateral high
refractive error (myopia or
hyperopia)

13. Clinical Assessment
• Case history- congenital cataract, constant strabismus, family history of
amblyopia
• Refractive error correction with cycloplegic refraction.
• Ophthalmoscopy- normal eye structure should be present in amblyopia.
• Visual acuity-
• No improvement on pinhole
• Crowding phenomenon(strabismic amblyopes)

14. Cont..
• Cover test-
• To check strabismus
• Observe accuracy and speed of fixation
• Binocular function-
• In the presence of strabismus- suppression
• Higher threshold for stereopsis
• Neutral density filter-
• Amblyopic eye-VA stable or potentially improve
• Organic defect- VA reduces

15. Severity of amblyopia
• PEDIG( Pediatric Eye Disease Investigator Group) has defined amblyopia as
• mild (20/30 or better)
• moderate (20/40-20/80)
• severe (20/100-20/400)

16. Management
• Optical correction
• Occlusion therapy
• Pharmacological treatment
• Various alternative therapies like:
• Dichoptic Training
• Perceptual Learning
• Video Games

17. Optical correction
• Any significant refractive error needs to be corrected
• Resolution of amblyopia in 1/3rd of patients
• Optical correction reaches in less than 15-18 weeks in most patients.

18. Occlusion
• First practiced in 900 AD
• Removal of light and/or form sense to the non-amblyopic eye, for defined
amount of time dependent on the level of vision of amblyopic eye.
• Types-
• Adhesive patch
• Material extension patch
• Bangerter occlusion foil

20. PEDIG Group recommendation for initial
occlusion
• For moderate amblyopia(20/40- 20/80)- 2hrs daily.
• For severe amblyopia(20/100- 20/400)- 6hr daily.
** If in moderate amblyopia if visual acuity fails to improve after 12 weeks- occlusion
time increased to 6 hours
## duration of treatment influenced by –
• Type of amblyopia
• VA deficit
• Age at the start of treatment

21. Penalization
• Atropine penalization- Atropine sulfate 1% , one drop 2times a week, better
eye
• Optical penalization-Plus lenses in spectacles
** Note- careful monitoring of visual acuity in both eye, is a must, to
ensure reversal amblyopia does not occur in non-amblyopic eye.

22. Comparison of amblyopia treatment modalities
Modality Patching Bangerter occlusion
foil
Atropine
Dose 2-6 hr daily, better eye Foil is worn on the
glasses full time
One drop twice
weekly, better eye.
Compliance variable Filter is not readily
visible, aids
compliance
Good, once instilled
effect last 1-2 week
Potential risk Skin irritation, allergy Poorly fitted glasses,
peeking around filters
Systemic side effect,
but rare
Amblyopia treatment
index
Less favorable score
compared to atropine
Lower treatment
burden compared to
patching
More favorable score
compared to patching

23. Recurrence of Amblyopia
• PEDIG- 24% recurrence, on cessation of treatment.
• Risk factors for recurrence-
• Previous recurrence
• Better visual acuity at point of cessation in the amblyopic eye
Those children using 6-8 hours of occlusion had four fold risk of recurrence-
Than reduction to 2 hrs before stopping occlusion.
• Compliance is most important

24. Reduced visual acuity in child
Careful history to include family history of
childhood eye problems
Cover test/extraocular movement/stereopsis
testing to detect any associated strabismus
and exclude any nerve palsy
Check normal pupillary reaction, color
vision, fundus and media to rule out organic
lesion(RAPD present – investigate further)

25. Cycloplegic refraction to detect refractive error-
prescribe glass- review every 6-12 weeks until vision
stable(period of refractive adaptation)
If no improvement- amblyopia- start with occlusion
therapy/penalization(after discussing with parents)
review 6-12 weeks, until no further improvement
If residual amblyopia, increase patching dose to 6
hrs, or optical/atropine penalization or switch
treatment modality
If maximum vision achieved, taper therapy, monitor
for recurrence.

26. Liquid Crystal Display Eyeglasses
• Spierer et al. and Erbagci et al. and Wang et al. found have more efficacy than patching.
• It is basically an occlusion therapy
• better compliance
• an alternative treatment.

27. Micro sensors
• Microsensor like Thera Mon (Thera Mon®-Chip, MC Technology GmbH) is
commercially available in 8*12 mm.
• To check the compliance of patching and glasses,
• Allows objective documentation of these therapies, by sampling the
surrounding temperature at regular intervals.

28. Recent
Therapies
Extrinsic
Augmentati
on
Levodopa Citicholine SSRI
Intrinsic
Augmentati
on
Dichoptic
Training
Perceptual
Learning
Vision
Therapy

29. Recent
Therapies
Extrinsic
Augmentati
on
Levodopa Citicholine SSRI
Intrinsic
Augmentati
on
Dichoptic
Training
Perceptual
Learning
Vision
Therapy

30. Pharmaco therapy
Levodopa
• deprivation amblyopia, dopamine levels in retina decreases
• amblyopia may improve with increasing level of dopamine
• Sofia et al. reported improvement in patients given levodopa and fulltime
patching compared to that ones’ given placebo

31. Citicholine
• Citicoline has both neuroprotective and cholinergic properties.
• When citicoline was added in run-in patch phase, it showed significant
improvement after 90 days of treatment.
• 500mg BD for 45 days, followed by 500mg OD for 45 days.

32. Other drugs
• SSRI, have shown to increase VEP in adults, but not significant
improvement in amblyopia was reported.
• Cholinesterase inhibitor, donepezil ( used in Alzheimer’s disease treatment)
helps in recovery of vision of amblyopic patients- boosts cholinergic
signaling.

33. Recent
Therapies
Extrinsic
Augmentati
on
Levodopa Citicholine SSRI
Intrinsic
Augmentati
on
Dichoptic
Training
Perceptual
Learning
Vision
therapy

34. Vision therapy
Orthoptics” or eye exercises or vision therapy
• eye-hand coordination exercises,
• anti suppression activities,
• accommodation activities,
• vergence activities in computer programs
generally done in office setting, supplemented with exercises at home.
adjunctive to patching

35. Perceptual learning
• performance on simple visual tasks shows improvement with practice
• improved visual acuity is due to lateral inhibition in the neural circuits with
the help of training
• effect can last for hours or even months without even continuous practice
• Done in office setting hence lacks popularity , needs more research.

36. Dichoptic therapy/binocular therapy
• images are shown dichoptically.
• low contrast image is shown in the healthy eye and high contrast image is
shown in the amblyopic eye.
• adapted into iPad device (CA, Cupertino, Apple) as a game of “falling
blocks”,
• to generate the dichoptic effect red-green eyeglasses used.
• Nonrandomised studies have shown good results,

38. Role of Refractive Surgeries
• In children having refractive amblyopia
• noncompliant with spectacles
• non-responsive to any conventional therapies.
• Correction of refractive amblyopia with surgery
• removes the usage of glasses
• improves global functioning in neurobehavioral disorders.
• Posterior chamber IOL and PRK better results

39. Thank You