Clinical features and natural history of the acute idiopathic enlarged blind spot syndrome

Objective: To study the clinical pattern and natural history of patients with the symptom of an enlarged blind spot. Design: A retrospective case series. Twenty-one patients were collected from a neuro-ophthalmologic practice during the period January 14, 1983, to July 1, 1996, and four consecutive patients were added from three vitreoretinal practices during the period April 14, 1986, to June 7, 1999. Participants: Twenty-six eyes of 25 patients were studied at onset and at repeat visits from 1 year and 7 months to 15 years and 6 months later. Methods: The first visit was composed of a complete neuro-ophthalmologic examination with fundus photos and fluorescein angiography in 12 of the 26 eyes. Follow-up examination consisted of an interval history, ophthalmologic examination, visual fields, fundus photographs, fluorescein angiograms in eight eyes, indocyanine green angiograms in seven eyes, and multifocal electroretinograms (mfERG) in both eyes of seven patients. Main Outcome Measures: The major outcome measures were onset and long-term visual field characteristics, disc and peripapillary features, association with other chorioretinal diseases, and mfERG features. Results: Twenty-one eyes had clinical features of chorioretinal syndromes, which are usually associated with an enlarged blind spot. Five eyes were examined too late after onset to expect such features. The visual field defect regressed in all but 12 eyes but never to an unequivocally normal-sized blind spot. Four of the 12 had chorioretinal scarring that corresponded to the permanent field defect. Twenty-one of 26 eyes had peripapillary scarring. The peripapillary scarring appeared the same no matter what the associated chorioretinal disease or type or size of field defect was. mfERG testing of seven patients at follow-up revealed first-order and second-order abnormalities long after clinical recovery, abnormalities that were bilateral even when the clinical signs had been unilateral. Conclusions: If an eye with an enlarged blind spot is examined within 2 weeks of onset, signs of a chorioretinal disease will usually be present. Beyond that period, signs such as disc congestion, disc staining, peripapillary retinitis, foveal changes, and peripheral retinal spots may not be present. Although the patient usually becomes asymptomatic, the blind spot is slightly and permanently enlarged, and there is usually peripapillary disc scarring. mfERG testing indicates that retinal damage is more widespread, bilateral, and permanent than the visual field and clinical features would indicate. Chorioretinal syndromes that are associated with a temporal field defect have some features in common and others that are distinctive.