Optic disc morphology in open-angle glaucoma compared with anterior ischemic optic neuropathies

Abstract

Purpose. To compare optic disc topography performed by confocal laser ophthalmoscopy in eyes with nonarteritic anterior ischemic optic neuropathy (NAION), arteritic anterior ischemic optic neuropathy (AAION), and open-angle glaucoma (OAG), adjusting for the amount of retinal ganglion cell (RGC) loss, as measured by nerve fiber layer (NFL) thickness and average visual field loss. Methods. At four referral centers, patients who met specific diagnostic criteria for OAG (103 persons, 152 eyes), NAION (53 persons, 57 eyes), or AAION (18 persons, 20 eyes) underwent Heidelberg Retinal Tomography (HRT; Heidelberg Engineering, Heidelberg, Germany), Stratus Optical Coherence Tomography (OCT; Carl Zeiss Meditec, Inc., Dublin, CA), and Humphrey visual field testing (HFA; Carl Zeiss Meditec, Inc.). HRT parameters were compared in univariate and multivariate models, accounting for degree of RGC loss by either OCT NFL thickness or visual field mean deviation (MD). Acute AION occurred at least 6 weeks before testing. Results. After adjustment for degree of injury according to either MD or mean NFL thickness, all HRT parameters were significantly different between OAG and both NAION and AAION. With similar damage, OAG eyes had larger, deeper cups; smaller rims; more cup volume; and less rim volume (all P < or = 0.001). There were differences in disc topography between NAION and AAION, but they were not consistent for both measures of damage. Disc area and MD were also significantly associated with many HRT parameters. NFL thickness was greater at the same MD for both AAION and NAION compared with OAG. Conclusions. NAION and AAION cause loss of RGCs, but have significantly different disc topography compared with OAG at a given level of RGC loss.

Figure 1.

Visual field MD versus average NFL thickness for the three groups in the study.

Figure 2.

Representative HRT images from each of the three groups. The images were selected from the patient in each group with MD closest to −25 dB. The cup was clearly much larger in the glaucomatous eye. In this particular example, the disc diameter was largest in the AAION eye, although the mean disc diameters of OAG and AAION eyes were similar and both larger than the mean NAION disc diameter.