This document discusses amblyopia, including its definition, etiology, neurological mechanisms, types, and treatment. It defines amblyopia as a reduction in best corrected visual acuity that cannot be attributed to structural eye abnormalities. The main types are strabismic, anisometropic, isoametropic, and deprivation amblyopia. Treatment involves full optical correction, occlusion of the better eye, and sometimes penalization of the better eye to encourage use of the amblyopic eye. Proper treatment is important during early childhood for amblyopia to be effectively reversed.

1. Amblyopia
Abdelmonem M. Hamed, MD
Professor of Ophthalmology Benha College of Medicine
Fellow of Baylor College, USA

2. • Definition:
– Unilateral or bilateral reduction of the best
corrected VA that can not be attributed to the
effect of any structural abnormality of the eye.
– Etiology:
– any cause of abnormal visual experience early
in life like squint, refractive error, etc…
• amblyopia
– affects the central vision
– the peripheral visual field remains normal
Amblyopia

3. • Neurological mechanism:
– not completely understood
– may be (proven in animal models)
• abnormality of neurons in LG Nucleus
• functional deficiency of cells of 1ry visual cortex
• crowding phenomenon:
– may be due to large neurons of the receptive
neurological field
– difficult recognition of the snellens letters if
they are closely surrounded by similar forms
Amblyopia

4. • Types of amblyopia:
– strabismic
– anisometropic
– isoametropic
– deprivation (amblyopia ex anopsia)
Amblyopia

5. • strabismic amblyopia
– the most common cause
– occur in the deviating eye
– mechanism
• competitive interaction between neurons carrying the
nonfusible input from the 2 eyes
domination of the cortical centers by the fixating
eye
reduced responsiveness of the non fixating eye’s
input
Amblyopia

6. • Anisometropic amblyopia
– 2nd in frequency
– due to unequal refraction in 2 eyes…..one retinal image is
defocused
– mechanism: the same as in strabismic amblyopia
– how much anisometropia required to cause amblyopia:
• hypermetropia from 1-2 D…….mild amblyopia
• astigmatism from 1-2 D…….mild amblyopia
• myopia > -6 D ………sever amblyopia
• myopia < -3 D usually does cause amblyopia
Amblyopia

7. • Isoametropic amblyopia
– large, equal, uncorrected visual acuity in both
eyes…..mild bilateral amblyopia
– how much bilateral refractive error required to induce
amblyopia
• hyperopia > + 5 D
• myopia > -10 D
• cylinder ??? May be > 3 D
Amblyopia

8. Amblyopia
• Deprivation amblyopia (disuse amblyopia) (amblyopia
ex anopsia)
– due to congenital or early acquired media opacity
– the least common type of amblyopia, BUT
– the most damaging and difficult to treat form
– in general, congenital cataract that are dense and occupy the
central 3mm or more of the lens must be considered capable
of causing sever amblyopia
–

9. Amblyopia
• Deprivation amblyopia
– any lens opacities acquired during childhood (up to age
8-10) can be almost harmful
– smaller polar cataract; around which retinoscopy can be
readily performed, and lammellar cataracts; around
which a reasonably good view of the fundus can be
obtained, may:
– cause mild to moderate amblyopia, or
• have no effect on visual development
– occlusion amblyopia is a form of deprivation amblyopia
caused by excessive patching

10. Amblyopia
• Eccentric fixation
– use of a particular nonfoveal region of the retina
for monocular viewing by an amblyopic eye
– detection
• major degrees
» noncentral position of corneal reflex
» VA: 6/60 or worse
• minor
» needs special tests such as Visuscopy, Haidinger’s
brushes or Maxwell's spot
» VA: mild acuity loss

11. • Cataract
– removal of cataract must be during the 1st 2-3
months of life
– in symmetric cataract, the interval between the
operation on the 1st and 2nd eyes, should be
not more than 2 week
– traumatic cataract in children 8-10 years old,
should be removed in few weeks
Treatment of amblyopia

12. Treatment of amblyopia
• Optical correction
– Rule: full correction
under cycloplegia

13. Treatment of amblyopia
• Occlusion
– full time: total occlusion of the
better eye is the most powerful
means of treating amblyopia
By
» adhesive patch
(recommended)
» spectacle mounted occluder
(take care of child peeking)

14. Treatment of amblyopia
• Occlusion
– part time:
» several days of patching
alternating W several days
of no patching
» daily patching for several
hours
» keep the child visually
active. How? No specific
visual exercises

15. Treatment of amblyopia
• Penalization of the better eye
» to make the better eye image
inferior to the amblyopic eye
» instill atropine ointment 1%,
once daily, in the better eye
» ± echothiophate iodide 1/8 %
may be administered in
amblyopic eye to potentiate
the near vision

16. Treatment of amblyopia