• We examined seven patients who had a syndrome of symptomatic monocular blind spot enlargement without optic disc edema. Two patients had previous blind spot enlargement that resolved over several months. The scotoma in each patient was absolute, measured 15° to 20° in diameter, had steep geographic margins, and extended to within 5° to 10° of fixation. Typically, patients had normal visual acuity, color vision, pupillary responses, and ophthalmoscopic findings. Photostress recovery, tested in two patients, was prolonged in the affected eye. Fluorescein angiography showed no abnormalities corresponding to the scotoma. Orbital computed tomographic scans in three patients and visual evoked responses in one patient were normal. Multifocal electroretinography, performed in two patients, showed loss of retinal waveforms in a large region surrounding the optic disc. Our findings suggest that retinal dysfunction produces this big blind spot syndrome, but we do not know its cause.