Factors influencing severity of and recovery from anisometropic amblyopia

To evaluate the correlation between the degree of anisometropia with depth of amblyopia and presence of stereopsis.

A retrospective chart review of 119 patients treated during 1995-2004 was carried out. All patients had undergone a full ophthalmological examination. Inclusion criteria were: anisometropia >1 diopter (spherical and/or cylindrical), age at first examination between 2 and 8 years, no previous optical correction, absence of ocular and neurological disorders, absence of ocular motility disorders, and minimum follow-up of 2 years (mean 7.9 +/- 4.3). Optical correction was prescribed at first visit and, at a second visit, the need for patching or penalization was evaluated.

The results show a correlation between the degree of anisometropia and visual acuity at first visit (p < 0.001). There were, however, several subjects with good levels of visual acuity despite considerable anisometropia, and also subjects where mild or moderate anisometropia was sufficient to induce a severe amblyopia. Compared to other types of anisometropia, anisomyopic patients appeared to have a higher degree of binocular vision recovery when corrected optically. First evaluation with the presence of good stereoacuity seems to be a prognostic indicator for amblyopic recovery.

This study demonstrates the difficulty of developing a guideline for screening and treatment of anisometropia. Even though there seems to be a correlation between type and degree of anisometropia in a majority of patients, there is also a significant number of cases that do not follow this pattern. Another important observation is the presence of binocular vision at the first evaluation as a good prognostic indicator for visual recovery with optical correction alone, even without penalization therapy.