Ambylopia

Question 1

what is the definition of unilateral ambylopia?

Answer 1

difference in BCVA of 2 lines or more between 2 eyes

Question 2

what is the definition of bilateral ambylopia?

Answer 2

BCVA of 6/12 or worse in both eyes

Question 3

what are the causes of ambylopia?

Answer 3

1) stimulus deprivation ambylopia: congenital cataract, congenital ptosis
2) strabismic ambylopia: one eye favoured for fixation all/almost all of the time, with cortical suppression of image from strabismic eye
3) Refractive amblyopia (refractive errors)

Question 4

what is the definition of anisometropic amblyopia?

Answer 4

significant difference in refraction (power) of the 2 eyes 🡪 one eye receives a clearer image than the other, occurs when difference in power between eyes is > 1.5D for hyperopia; > 3-4D for myopia; > 1.5D for astigmatism

Question 5

what is the definition of ametropic/isometropic amblyopia?

Answer 5

bilateral high refractive errors 🡪 blurred retinal images in both eyes, occurs when power of affected eye is > 5D for hyperopia; > 8D for myopia

Question 6

what is the definition of meridional amblyopia?

Answer 6

unilateral or bilateral high astigmatism (>2.5D in affected eye(s)) 🡪 blurred retinal images in one or both eyes

Question 7

how is amblyopia managed?

Answer 7

Provide a clear retinal image

• Refractive: full-time spectacle wear (throughout period of visual immaturity), KIV atropine if myopia is rapidly progressing
• Stimulus deprivation: remove all obstacles in visual axis, e.g. taping upper eyelids for visually significant ptosis, surgical ptosis correction; cataract surgery for visually significant cataract

Correct ocular dominance

• Occlusion therapy: patch better-seeing eye, so that amblyopic eye takes up fixation (patch X hours/day, increase X over time)
• Atropine penalisation: 0.5% or 1% atropine eyedrops used to blur vision in better-seeing eye so that amblyopic eye takes up fixation

Parent & child education and involvement
-Treatment is effective only within the critical period (<8-9 years); treatment is increasingly difficult as the child grows older and visual system becomes less plastic (hence importance of treatment compliance while visual system is still plastic)

If strabismus component is significant, may need to consider strabismus surgery