Purpose: To elucidate the pathophysiology of the diseases recently grouped under the name of acute zonal occult outer retinopathy (AZOOR). Methods: Twenty-four patients with the diagnosis of multiple evanescent white dot syndrome, acute idiopathic blind-spot enlargement syndrome, acute macular neuroretinopathy, multifocal choroiditis, or pseudo-presumed ocular histoplasmosis syndrome, or a combination of these diagnoses, were evaluated on one or more visits with fullfield electroretinograms (ERGs) and kinetic and static perimetry. Sera and IgG fractions were tested using immunofluorescence on cryostat sections of fixed and unfixed human and rat retina. Results: Patients with AZOOR as a group showed abnormal results for all eight ERGs and two visual field parameters measured. Interocular asymmetry was a prominent feature of the patients' test results. Logistic regression indicated that interocular differences in ERG parameters significantly increased the efficacy of identifying patients with AZOOR beyond that of the parameter values alone. Visual field area correlated well with ERG a-wave amplitude. Serial visual function tests in a subset of patients showed that there could be short-term partial recovery or progressive loss of function. Autoantibodies to a specific retinal cell type were not detected. Conclusions: All patients with AZOOR showed a pattern of visual dysfunction that was photoreceptor in origin, patchy in its distribution across the retina, and asymmetric in the two eyes. There was considerable variability in the severity and the natural history of retinal dysfunction in the patients studied. The full-field ERG was found to be a valuable adjunct in diagnosing AZOOR, especially when the expected interocular variation in measured parameters was known for control subjects. No evidence was obtained for autoantibodies to any retinal cell type in the patients with AZOOR who were tested.
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