 evok respons visual disord 1 erg ver record eyelid later occipit electrod respons diffus stroboscop stimul 45 normal subject ver compos earli triphas potenti aris occipit region wave 67 percent subject wave ii 97 percent wave iii 100 percent wave inconst contain compon vertex refer asymmetri ver left normal subject averag asymmetri smaller side compar larger 19 percent 12 5 monocular stimul contralater ver regularli larger ipsilater reflect predomin retin represent tempor field 2 statist determin criterion 50 percent depress wave ii identifi patient hemianop defect involv central 10 percent visual field tangent screen campimetri latenc asymmetri msec grossli asymmetr aberr wave form patient diffus cerebr diseas hemianop defect 3 sever diffus retin diseas associ alter loss erg ver stimul involv ey 4 optic nerv diseas indic bilater loss suppress ver stimul involv ey erg normal 5 bilater prechiasm involv associ complet suppress ver wave ii lost diseas conclus demonstr 6 involv nasal retin fibr indic revers normal contralater preponder ver monocular stimul chang observ chiasmal diseas 7 retrogenicul blind associ loss earli ver preserv late respons nonspecif project felt contribut late cortic respons photic stimul 