A case report of acute zonal occult outer retinopathy

Purpose: To describe the diagnostic complexities of a patient with acute zonal occult outer retinopathy. Case report: A healthy female presented with acute bilateral visual field loss and photopsia. On initial examination, her visual acuity, colour vision, fundus examination and fluorescein angiography were normal. Fundus autofluorescence, however, revealed scattered hyperautofluorescence in both eyes and electrodiagnostic tests were abnormal. A differential diagnosis including acute zonal occult outer retinopathy was postulated and serology requested. The patient's past medical history included both breast and endometrial cancer and raised the possibility of cancer-associated retinopathy. A normal full-body positron emission tomography scan, negative antibodies for cancer-associated retinopathy and abnormal electroretinogram led to a diagnosis of acute zonal occult outer retinopathy. Conclusion: It has been more than 20 years since Gass first described the syndrome of acute zonal occult outer retinopathy. Typically affecting young, healthy females, acute zonal occult outer retinopathy is characterised by photopsia, minimal fundoscopic changes and electroretinographic abnormalities. Visual field loss is permanent and often associated with slow-progressing degeneration of the retinal pigment epithelial cells. Retinal photoreceptor dysfunction is an uncommon and unrecognised cause of acute visual loss. Acute zonal occult outer retinopathy should be considered as a differential diagnosis in those patients with deceptively normal fundal examinations, abnormal electroretinograms and visual field loss.