The Function of the Fellow Eye in Patients with Unilateral Nonarteritic Anterior Ischemic Optic Neuropathy

Purpose: To investigate the function of the fellow eye in patients with unilateral nonarteritic anterior ischemic optic neuropathy (NAION). Methods: From 2009 to March 2018, 18 patients with NAION who underwent bilateral visual field examinations and follow-up visits at least two times were enrolled in this study. Initial visual acuity, final visual acuity, degree of visual field defects, the cup-disc (C/D) ratio of the fellow eye, and the presence or absence of cardiovascular disease was retrospectively analyzed using medical records. Results: The fellow eye mean best-corrected visual acuity was 0.03 +/- 0.53 (logMAR) and the mean visual field defect was -4.68 +/- 3.65 dB in 18 eyes of patients with unilateral NAION (p = 0.007 and p = 0.001, respectively). The C/D ratios were divided into two groups: > 0.3 and < 0.3. The visual field defect was improved significantly from -4.92 dB to -2.37 dB in the group with optic disc ratios < 0.3 (p = 0.013). When the changes in visual field defects were analyzed according to the presence or absence of cardiovascular disease, the visual field defects were improved from -5.65 dB to -4.49 dB in patients with cardiovascular disease, and improved from -3.69 dB to -1.46 dB in patients without cardiovascular disease (p = 0.025 and p = 0.021, respectively). Conclusions: In patients with unilateral NAION, reduced function in the fellow eye may appear temporarily, so a visual field examination should be performed in both eyes. The possibility of incipient NAION should be considered in patients with visual field abnormalities in the fellow eye.