Case of acute zonal occult outer retinopathy with abnormal pattern visual evoked potentials

Electrophysiological and morphological findings were studied in a case of acute zonal occult outer retinopathy (AZOOR) showing abnormal pattern visual evoked potentials (VEPs) at the onset and significant functional recovery in the natural course. A 21-year-old woman presented with acute onset of photopsia and a large scotoma in the right eye of 2 weeks duration. Her visual acuity was 20/20 in both eyes with no ophthalmoscopic and fluorescein angiographic abnormalities. However, a relative afferent pupillary defect and an enlarged blind spot were found in the right eye. The pattern VEPs were severely reduced when the right eye was stimulated. The amplitudes of both rod and cone full-field electroretinographics (ERGs) were reduced in the right eye. The amplitudes of the multifocal ERGs were reduced in the area of the enlarged blind spot. Irregularities in the inner segment/outer segment (IS/OS) line of the photoreceptors were observed over the nasal fovea by optical coherence tomography (OCT). The patient was followed without treatment. The enlarged blind spot disappeared in 3 months after the onset. At 5 months, reappearance of the IS/OS line was detected by OCT. At 6 months, the P(100) recovered to normal values. At 1 year, the reduced full-field ERGs were almost normal size and the multifocal ERGs in the area corresponding to the enlarged blind spot were also improved. ERG findings are crucial for differentiating AZOOR from retrobulbar neuritis, especially in patients with abnormal pattern VEPs. The pattern VEPs, full-field ERGs, multifocal ERGs, and OCT images can be abnormal in the early phase of AZOOR, but they can all improve during the natural course.