The Classification of Amblyopia on the Basis of Visual and Oculomotor Performance

Abstract

Amblyopia is most simply defined as a loss of visual acuity without an identified organic cause. Traditionally, the amblyope is roughly classified as strabismic, anisometropic, refractive or deprivational, according to the accompanying condition thought to be responsible for the acuity loss. Although it is widely recognized that these classes are neither particularly uniform nor discriminative, there is no established means of classifying amblyopes on the basis of visual function alone. Our primary objective is to create a classification system for amblyopia, based on a broad spectrum of clinical, psychophysical and oculomotor abnormalities -- a system that could supplement or supplant the traditional approach leading to better diagnosis and treatment. We here report the results from a pilot study showing that this objective is feasible. Two hundred and fifteen naive subjects, including eighty-two amblyopes, seventy-three recovered amblyopes, forty non-amblyopic strabismic or anisometropic ("at risk") subjects, and twenty normal subjects, participated in the study. The results from numerous psychophysical and oculomotor tests were analyzed statistically to determine if clusters of subjects with similar visual and oculomotor capabilities would emerge from the data base. Cluster analysis identified nine separate clusters. The laboratory measurements were sufficient to predict cluster membership and accounted for between-cluster variation, including whatever variation was due to Snellen acuity and clinical diagnosis.