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J. Felius, D.R. Stager, D.R. Weakley, E.E. Birch; Inter-eye Differences in Accommodation in Anisometropic Children with and without Amblyopia . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4801.
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Purpose: The risk for anisometropic amblyopia increases with the difference in refractive error between the eyes. Amblyopia typically develops in the more hyperopic eye. Patients with >3 D anisometropia are at high risk, but only about half of those with 1 D to 2.5 D anisometropia become amblyopic. It is possible that a mild to moderate amount of anisometropia can be compensated by some patients through asymmetric accommodation to prevent amblyopia. In an initial study to evaluate this hypothesis, binocular accommodation was measured in anisometropic children and inter-eye asymmetries were related to the presence of amblyopia. Methods: A PowerRefractor digital photoscreener was used to measure binocular accommodation in 20 children, ages 0.9 – 12 years (median 3.8 y) with 0.75 – 10 D (median 2.1 D) anisometropia. Patients had severe (>0.8 logMAR, n = 4), mild (0.3 – 0.8 logMAR, n = 4), or no (<0.3 logMAR, n = 12) amblyopia. With the PowerRefractor at 1 m from the eyes, fixation targets were inserted at 5 viewing distances from 0.25 to 3 m, to assess the relationship between accommodative response and demand. Results: As expected, the amount of anisometropia was strongly associated with the amount of amblyopia (r = 0.74, p < 0.001). For 13 patients the inter-eye refractive difference was approximately constant across viewing distances and corresponded to their cycloplegic refraction, with the non-amblyopic or less hyperopic eyes showing the most accurate accommodation in 10 of 13 cases. However, in 2 amblyopic and 2 non-amblyopic patients the refractive differences measured by the PowerRefractor were smaller than expected on the basis of their cycloplegic refraction, suggesting that asymmetric accommodation partially compensated the anisometropia. Three additional amblyopic eyes showed virtually no change in refractive status across viewing distances. Conclusions: Rapid assessment of accommodation as a function of viewing distance in children as young as 1 year of age can identify inter-eye differences in accommodation. As expected, the non-amblyopic and/or less hyperopic eyes dominated the accommodative response. The finding of asymmetric accommodation in several mildly anisometropic children with no or mild amblyopia suggests that it may play a role in preventing anisometropic amblyopia.
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