AMBLYOPIA #2: Investigating it

• Accurate H&S

Age of onset of strab, previous treatment (rx, occlusion, other - when given, for how long, successful? Why stopped?)

• Acuity assessment

Crowding: first thought to be specific to amblyopia. People demonstrate better acuity for widely spaced targets and when letters are brought closer together giving contour interaction acuity is reduced. VA must be measured w/optimum Rx. Try and measure line and single letter acuity under standard illumination etc

• Neutral Density Filters - Functional Vs Organic Amblyopia
  

VA is similar in each eye under mesopic vision but is reduced @ photopic levels. Von Noorden and Buren (1959) found that as luminance levels decreased the difference in VA decreased and at the lowest luminance levels the VAs were similar. Px w/functional amblyopia didn't see an improvement in the VA of the amblyopic eye from light to dark, but the VA simply decreased less than that of the normal eye. Px w/organic amb. --> VA decreased in similar manner both eyes.

The ND filter can also help differentiate between eccentric fixation and macular function type people.

• Dark adaptation

Wald & Burian found that dark adaptation is normal in amblyopes but there is a slight elevation in central threshold.

• Evaluation & Prognosis

If you're going to suggest treatment first think

1. Am I going to cause intractable diplopia?
2. Type of amblyopia - the relative importance of rx correction/strab correction
3. Age of px - younger is better, must be under 10, co-operation - understanding of exercises, ease of patching?
4. Duration of amblyopia - shorter = better
5. Acuity - poor acuity = worse prognosis

Treatment tomorrow.