Visual field abnormalities in nonarteritic anterior ischemic optic neuropathy: their pattern and prevalence at initial examination.

OBJECTIVE To evaluate the pattern of various types of visual field defects and their prevalence at initial examination of nonarteritic anterior ischemic optic neuropathy (NA-AION). METHODS The data were compiled from 312 consecutive eyes (in 265 patients) that fulfilled our inclusion and exclusion criteria. A comprehensive ophthalmic evaluation was performed, including recording of visual acuity, visual fields with a Goldmann perimeter (using I-2e, I-4e, and V-4e targets regularly), and intraocular pressure; slitlamp examination of the anterior segment; ophthalmoscopy; color fundus photography; and in acute cases, fluorescein fundus angiography. The visual field defects were divided into 2 groups: (1) general field defects and (2) various types of scotoma in the central 30 degrees . The prevalence of various types of visual field defects was estimated for I-2e, I-4e, and V-4e isopters by dividing the total number of eyes with the defect by the total number of eyes that could see that particular target. Exact 95% confidence limits for the prevalence were computed. RESULTS Of the 265 patients, 169 (63.7%) were male and the mean +/- SD patient age was 55.0 +/- 9.1 years. The median interval between the first visual field test and the onset of NA-AION was 2 weeks. Of the 312 eyes, the I-2e target was seen by 75.3%, the I-4e target by 90.7%, and the V-4e target by 100%. Overall prevalence of general visual field defects was 83.4% with I-2e, 78.8% with I-4e, and 68.9% with V-4e, whereas the prevalence of scotoma(s) within the central 30 degrees was 55.3%, 49.5%, and 36.2%, respectively. Central scotoma was seen in 48.5% with I-2e, 43.8% with I-4e, and 29.2% with V-4e. A detailed prevalence of various types of visual field defects is given. Relative inferior altitudinal defect was most common (34.9% with I-2e and 22.3% with I-4e), but the absolute inferior altitudinal defect was seen in only 8.0%. By contrast, absolute inferior nasal sector visual loss was the most common defect detected in NA-AION (22.4%), but it occurred in only 3.4% with I-2e and 11.0% with I-4e. Overall, loss of the nasal part of the visual field was the most common occurrence. CONCLUSIONS Our study demonstrated that NA-AION eyes may initially show a variety of optic nerve-related visual field defects. Our study also showed that an absolute inferior nasal visual field defect is much more common (22.4%) than an absolute inferior altitudinal visual field defect (8.0%) in NA-AION and could be considered the most characteristic single field defect in NA-AION. We found that a combination of relative inferior altitudinal defect with absolute inferior nasal defect is usually the most common pattern in NA-AION.