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We performed electrophysiologic testing in 10 patients with abetalipoproteinemia (ABL). Peripheral nerve studies implied an axonal disorder. Visual evoked potentials demonstrated prolonged P100 latency in three patients and abnormal electroretinograms in six. Somatosensory evoked potentials indicated dorsal column dysfunction in eight patients. Brainstem auditory evoked potentials were normal. Findings were consistent with the known neuropathology of ABL and of experimental vitamin E deficiency. Stabilization or improvement in electrophysiologic findings occurred with vitamin E supplementation. Neurophysiologic tests document retinal, central somatosensory and peripheral nerve lesions in vitamin E deficiency and provide an objective indication of response to treatment.

were re-evaluated 6-55 months later to determine whether ocular neovascularisation had developed. Of the 21 CRVO eyes, 6 (29%) were subnormal to red in the affected compared with the normal fellow eye. At follow-up, all 6 (100%) patients had developed ocular neovascularisation compared with 1 (7%) of the 15 patients who were supernormal to red (p = 0.00013).Cone ERG subnormality to red flash in CRVO eyes compared with normal fellow eyes may be a predictor of later development of ocular neovascularisation.Central retinal vein occlusion (CRVO) is a common retinal disease. 1 Follow-up studies of patients with CRVO have shown that 20-30% of patients may develop neovascularisation of either the iris, the anterior chamber angle or optic nerve. 1 -4 The stimulus for anterior segment and retinal neovascu larisation, although poorly understood, is thought to be related to severe retinal ischaemia. 5 For those patients with iris neovascularisation, early pametinal laser photocoagulation is effective in causing ocular neovascularisation to regress, while delayed photo coagulation usually results in a painful blind eye. 6 -10 Various clinical, l1 angiographic 5 , 12 and electrore-.h ' 1 3 -18 tmograp IC parameters have been used to predict which patients are at risk of developing ocular neovascularisation. However, none of them has been shown to be either sensitive or specific enough to identify all CRVO eyes in which neovascularisation will develop.We have previously reported that in most patients with CRVO, the amplitude of the cone electroreti nogram (ERG) b-wave is larger in the affected compared with the unaffected eye if the retina is sufficiently light-adapted and the test stimuli are of long wavelength. I9 We have called this 'supernorm ality to red'. This supernormality is unexpected since CRVO has usually been reported to decrease the amplitude of the flash ERG. 13 -15 , 18 , 20 , 21 We also observed that a minority of CRVO eyes, however, do not show this ERG supernormality to red flashes. In fact, they are subnormal to red in the affected compared with the unaffected eye, i.e. the ratio of the cone ERC b-wave amplitude to red in the CRVO eye to that in the normal fellow eye was less than l. In order to further elucidate the significance of differences in cone ERG responses to red in CRVO eyes, we decided to do a follow-up study of patients who had undergone an ERG at the time of diagnosis of the vein occlusion. We hypothesised that CRVO eyes which showed cone ERG subnormality to red flash compared with normal fellow eyes (ratio <1) would later develop ocular neovascularisation. The purpose of this paper is to report our findings. SUBJECTS AND METHODSIncluded in the study was a consecutive series of patients with unilateral CRVO and no abnormality of the fellow eye recruited from among patients either attending the general or retina clinics or referred by private physicians for an ERG. At the time the ERG was obtained, none of the patients had any evidence of neovascularisation of either the