[The function of contrast sensitivity in deprivation amblyopia]

Abstract

Visual deprivation during the first few months of life is known to result in a severe and irreversible visual deficit. Animal models of amblyopia developed during the past 20 years has considerably increased our knowledge of the "sensitive period" during which deprivation can lead to irreversible effects, and of the anatomical and physiological changes underlying this visual deficit. However precise data regarding either the duration of the sensitive period or the nature of the amblyopic deficit are still mostly lacking in humans. Preliminary results on the latter topic are reported in the present paper. Contrast sensitivity function (CSF) has been studied using stationary sinusoidal gratings in three patients with deprivation amblyopia resulting from bilateral congenital cataracts and in nine normal emmetropic subjects. Compared with these control subjects, the three amblyopic patients showed a dramatic decrease of their CSF with a maximal drop in the high and medium spatial frequency range and a relative sparing at low spatial frequencies. Within the framework of current theories of parallel processing of visual information through the geniculostriate pathway, these results indicate that early visual deprivation in man severely affects development of "sustained" channels involved in form perception. Further studies are underway to explore "transcient" channels in similar cases.