Age-related decline of disc rim area in visually normal subjects.

Optic disc parameters and axial lengths were measured in 81 visually normal young and elderly white adults (young [n = 41]: 27.2 +/- 5.7 years versus elderly [n = 40]: 68.8 +/- 8.4 years) using Rodenstock Optic Disc Analyzer and A-scan sonography. Axial lengths correlated positively with optic disc parameters (Spearman correlation analysis: rim area: P = 0.042, disc area: P = 0.052, and cup volume: P = 0.010). Older subjects had a shorter axial length (23.09 +/- 1.02 mm) and smaller disc rim area (1.171 +/- 0.338 mm2) than younger subjects (23.60 +/- 1.15 mm and 1.325 +/- 0.314 mm2; Mann-Whitney U test: P = 0.011 and P = 0.013, respectively). While both axial length and disc rim area declined with age (0.011 mm and 0.003 mm2 per year; Spearman correlation analysis: P = 0.032 and P = 0.020, respectively), the cup-to-disc and rim area-to-disc area ratios appeared to remain relatively constant throughout adult life. The age-related decline of disc rim area is consistent with histologic evidence of age-related decline of ganglion cell axons. The rim area-to-disc area ratio seems less affected by age, and is thus a better parameter to isolate age-related change from disease-related change of optic nerve in a longitudinal follow-up of diseases involving the optic nerve head.