[Amblyopic eyes produce an abnormal electroretinogram in pattern presentation with the on-off technique]

In amblyopic subjects the electroretinogram in response to pattern stimuli (P-ERG) has been variously described as normal or abnormal. While this was found with a reversing stimulus pattern, we presently recorded the P-ERG by exposing the eye to a checkerboard pattern (element size 10, 30, or 60 min of arc) alternating with a uniform field of equal mean luminance (5 or 500 cd/m2). Eight subjects with anisometropic or squint amblyopia and ten normal subjects took part in the investigation. No differences in P-ERG amplitudes were found in amblyopic eyes in response to pattern offset. However, the P-ERG to pattern onset was diminished in the amblyopic eyes compared with the healthy fellow eyes and with the eyes of normal subjects. Both the early positive (p-q) and the late negative (q-r) components of the onset response were affected. Furthermore, the normal amplitude profile of the onset response (largest response at 30 min, smaller responses at 10 and 60 min, i.e. pattern tuning) was lost in the amblyopic eyes. According to Arden [2] and Korth [9], the P-ERG in response to pattern onset represents the pattern component and that in response to pattern offset, the luminance component. From this we conclude that in subjects with anisometropic and squint amblyopia the retinal information processing of pattern stimuli is disturbed, whereas that for luminance discrimination remains normal.