OBJECTIVE: Changes in retinal sensitivity to light have been hypothesized as etiological in seasonal affective disorder. This study was undertaken to investigate sensitivity to light in seasonal affective disorder using electrooculography (EOG), an objective measure of retinal light response. METHOD: In a mood disorders clinic, 19 depressed, drug-free patients with seasonal affective disorder, diagnosed by DSM-III-R criteria, were compared with 19 age- and sex- matched normal comparison subjects. All subjects had identical EOG testing performed during the winter. EOG (Arden) ratios were calculated from the EOG data. RESULTS According to multivariate analysis of variance, the EOG ratios in the patients with seasonal affective disorder were significantly lower than those of the normal comparison subjects, although there was considerable overlap in EOG ratios between patients and comparison subjects. CONCLUSIONS: These results suggest that seasonal affective disorder is associated with subtle retinal abnormalities at the level of the photoreceptor/retinal pigment epithelium complex, consistent with subsensitivity to light. A limitation of this study is that the retinal origins of the EOG response are nonspecific and still not completely elucidated.Abstract Teaser