Neuroretinal rim area in diabetes mellitus.

Neuroretinal rim area (NRA) may indicate the amount of viable optic nerve tissue. Changes in the NRA have been found to occur in people with glaucoma. We sought to determine whether there were effects of retinopathy and intraocular pressure (IOP) on NRA in eyes of people with diabetes. Measurements of optic discs and cups were taken from 35-mm stereoscopic slides taken with a Zeiss fundus camera. The photographs were taken during a population-based study. The difference between disc and cup area was taken to be the NRA. Median photographic NRA from 2085 right eyes was 10.5 mm2. In younger- and older-onset persons, NRA showed a tendency to increase with age and, inconsistently, with the severity of diabetic retinopathy; it decreased with increasing IOP in older-onset persons not taking insulin. The cohort was reevaluated 4 yr later. NRA increased in all groups. Measurements from photographs taken of a nondiabetic comparison group showed no change over the same interval. These data suggest that NRA may be affected by diabetes. This could be due to nerve swelling.