Purpose: To evaluate correlations between retinal nerve fiber layer (RNFL) thickness with visual field (VF) sensitivities in eyes with nonartertic anterior ischemic optic neuropathy (NAION). Design: Case-control study in an academic, institutional setting. Methods: One eye from 21 patients with NAION and 32 healthy participants were included in this prospective study. Humphrey visual field (HVF) sensitivities were obtained from standard achromatic HVF test (24-2 SITA). RNFL was measured with scanning laser polarimetry (SLP, GDx-VCC) and optical coherence tomography (OCT, StratusOCT). Correlations were evaluated between RNFL and sensitivities from global, hemifields, and regional locations of the VF pertinent to the RNFL distribution. A total of 15 NAION eyes had inferior altitudinal HVF defects, and their global and regional RNFL was compared with that of control eyes. The main outcome measure was correlation between HVF sensitivities and RNFL. Results: Correlations of global, hemifield, and sectorial HVF sensitivities with RNFL were greater when RNFL was measured with OCT than with SLP, except for nasal and inferonasal sectors. RNFL thickness was far lower in the hemiretinas corresponding to the relative unaffected hemifield in eyes with altitudinal VF defect compared with controls. Conclusions: In patients with NAION, RNFL measured by OCT provided better correlation to HVF changes than SLP did. Both instruments showed decreased RNFL in NAION eyes with altitudinal VF defects compared with control eyes, demonstrating loss of RNFL even in sectors of the optic disk that corresponded to relatively unaffected hemifield, suggesting greater damage beyond the extent estimated by VF methods. © 2007 Elsevier Inc. All rights reserved.