Acquired unilateral loss of dark adaptation.

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Poor dark adaptation is a not uncommon symptom and may occur in a wide variety of diseases but its occurrence in one eye only is far less frequent. When it occurs unilaterally, an obvious ocular disease is generally present to account for it and visual functions other than that of dark adaptation are also depressed. Some subjects with poor dark adaptation may have no demonstrable ocular lesion nor any other defect of visual function. Almost always they have one of the forms of congenital night blindness but sometimes the trouble is the first evidence of a progressive tapeto-retinal degeneration. Electrophysiological studies of the retinal function of these patients have proved to be useful, and Armington and Schwab (I954) have shown that by using electroretinography patients with a non-progressive night blindness can be differentiated from those with a progressive tapeto-retinal degeneration. Auerbach, Godel, and Rowe (i969) have similarly studied a large series of patients with night blindness. They have shown that patients with an apparently stationary night blindness fall into two main groups, but they also note that progression of the condition may occur. An acquired form of night blindness without obvious ocular defects and without disturbance of any other ocular function was described by Kelsey and Arden (I969) in which electrophysiological tests of retinal function suggested a lesion at the level of the bipolar cell layer. Two patients with similar acquired changes which were strictly uniocular are described below.