The other side of amblyopia

Abstract

Amblyopia is defined as a loss of letter recognition visual acuity in the affected eye; however, studies in both nonhuman primates and man have shown that other important aspects of vision, including color, motion, and contour perception, are also abnormal. The anatomical changes that occur in the lateral geniculate nucleus and visual cortex following monocular visual deprivation affect both eyes and follow very different patterns with deprivation that begins at different ages and differ markedly in the magnocellular and parvocellular pathways. The interactions between the eyes and the requirements for recovery are very different following onset at different ages and differ for magnocellular and parvocellular pathways. Electrophysiological and psychophysical studies in man show different patterns of change in patients with strabismic amblyopia of early and late onset and abnormalities of color and motion processing that affect both amblyopic and fellow eyes and differ with age of onset. Abnormal visual experience also has more general effects on development, with amblyopic children showing abnormalities of eye-hand coordination when using either their amblyopic or fellow eyes, and abnormalities of reading. Differential effects of abnormal visual experience and treatment on magnocellular and parvocellular pathways may account for some of the visual deficits and treatment failures seen in amblyopia.