AMBLYOPIA

1. AMBLYOPIA Dr Cynthia Arunachalam Prof and HOD

2. Amblyopia • Partial loss of sight in one or both eyes in the absence of ophthalmoscopic or other objective signs of ocular disease. • Critical period – birth to 6 years of age

3. Types of Amblyopia • 1. Strabismic amblyopia • 2. stimulus deprivation amblyopia • 3. Anisometropic amblyopia • 4. Isometropic amblyopia • 5. Meridonial amblyopia • Strabismus (misaligned eyes) • Media opacity • High refractive errors

4. Amblyopia: Three Main factors • 1. Media opacity • 2. High refractive errors • 3. Strabismus (misaligned eyes) • 1. Light/stimulus deprivation • 2. Visual / form sense • 3. Abnormal binocular interaction

5. Stimulus deprivation amblyopia • Congenital cataract • Ptosis • Corneal opacity

6. Stimulus deprivation amblyopia • Best example: monocular congenital cataract • Total deprivation of sensory input to cortex in one eye with normal sensory input in fellow eye leads to rapid dense amblyopia

7. Stimulus deprivation amblyopia: Cataract Treatment: • urgent cataract surgery (clearing of media opacity) • may patch both eyes prior to surgery to prevent amblyopia • contact lens to restore focus • diligent patching of unoperated eye after surgery

8. Stimulus deprivation amblyopia: Others • Other obstruction /opacity preventing light from reaching the retina • Ptotic (drooping) upper eyelid • Corneal scar/opacity • forceps injury at birth • hereditary abnormalities • Vitreous opacity, hemorrhage

9. Stimulus deprivation amblyopia: Treatment • Clear the media • surgically lift ptotic eyelid • corneal transplant • cataract removal

10. High Refractive Errors Clear input to the visual cortex is required to develop good vision • Myopia (nearsighted) • eye too long • Hyperopia (farsighted) • eye too short • Astigmatism (distortion)

11. High Refractive Errors • If retinal image in one eye is severely unfocussed, unilateral amblyopia may result – anisometropicamblyopia • If retinal image in each eye is severely unfocused, bilateral amblyopia may result (uncommon) – isometropicamblyopia • high hyperopia • high myopia • high astigmatism • If retinal image is unfocussed in one meridian only, - meridonialamblyopia may result

12. Anisometropic Amblyopia • Higher refractive errors in one eye as compared to the other eye. • Hypermetropia 1-2 D • Myopia 3 D

13. Anisometropic Amblyopia • If retinal image in one eye is unfocused, monocular amblyopia may result (very common) • anisometropia (e.g. one eye normal, one eye moderately farsighted) • often seen in combination with accomodative esotropia

14. Isometropic Amblyopia • Bilateral High refractive errors • Bilateral Amblyopia

15. Meridonial amblyopia • Uncorrected astigmatism • Selective for the specific visual meridian

16. Refractive Amblyopia: Treatment • Glasses - clears retinal image • Patch the better eye - forces brain to use image from “weaker” eye

17. Strabismic Amblyopia • Unilateral constant squint. • Prolonged uniocular constant suppression.

18. Amblyopia: Prevention/Early Treatment • Awareness of problem • Overall affects 2-5% of population

19. Amblyopia: Prevention/Early Treatment Birth • First examination by primary care doctor before newborn leaves hospital • Look for clear, equal red reflex • congenital cataract • hereditary corneal dystrophies • Ocular alignment unreliable in first week of life

20. Amblyopia: Prevention/Early Treatment Birth to 2 Years Examination at each well baby check – 3 points • 1. Red reflex • 2. Ocular alignment should be orthophoric by 3-6 months • corneal light reflex, alternate cover test • if alignment not straight by 3 months - refer to ophthalmologist • 3. Visual acuity - fix and follow smoothly by 6 months • check each eye separately

21. Amblyopia: Prevention/Early Treatment 2 Year Check • Red reflex - Bruckner Test • direct ophthalmoscope at 0 power setting, otoscope without magnifier • distance of 2 feet from patient • normal - equal red reflex • unequal refraction - one eye darker reflex • no/poor reflex - media opacity • corneal light reflex not symmetric - strabismus

22. Amblyopia: Prevention/Early Treatment • Ocular alignment corneal light reflex alternate cover test • Visual acuity fix and follow very smoothly and consistently ask the parent what the child sees - “he sits close to TV” can the child recognize the parent across the room

23. Amblyopia: Prevention/Early Treatment 6+ Year Checks • Ocular alignment – perfect • Visual acuity - Snellen letters preferable • vision should be 6/6 or better • refer for vision < 6/9 or 2 line difference (i.e. 6/6 one eye, 6/12 other) • External, Anterior segment, Ophthalmoscopicexam

24. Clinical characteristics • 1. visual acuity: recognition acuity > affected than resolution acuity • 2. Neutral density filter: improvement in visual acuity • 3. Crowding phenomenon: VA is better with single charts • 4. Fixation pattern: degree of amblyopia, central or eccentric • 5. Colour Vision: affected in deep amblyopia

25. Amblyopia: Conclusion • Straighten the eyes • Clear the media • Correct the refractive error • Occlusion therapy

26. OCCLUSION THERAPY • Forcing the use of the amblyopic eye by occlusion of the other eye by patching. • Occlusion therapy has been the mainstay of treatment since the 18th century.

27. OCCLUSION THERAPY • Patching may be full-time or part-time. • Children need to be observed at intervals of 1 week per year of age, if undergoing full-time occlusion to avoid occlusion amblyopia in the sound eye. • The Amblyopia Treatment Studies (ATS) have helped to provide new information on the effect of various amounts of patching.[14, 15]

28. OCCLUSION THERAPY Patching may be by • adhesive patches, • opaque contact lenses, • occluders mounted on spectacles, • adhesive tape on glasses • full-time patching produced a similar effect to that of 6 hours of patching per day • Always consider lack of compliance in a child where visual acuity is not improving.

32. Amblyopia: Conclusion Diagnose it early!