OPTIC DISK, CUP AND NEURORETINAL RIM SIZE, CONFIGURATION AND CORRELATIONS IN NORMAL EYES

Abstract

Four hundred and fifty-seven unselected normal human optic nerve heads of 319 subjects (163 men, 156 women, mean age 42.7 .+-. 19.6 years) were evaluated by magnification-corrected morphometry of optic disc photographs. Mean optic disc surface measured 2.69 .+-. 0.70 mm2 (0.80-5.54 mm2), mean diameter horizontally 1.76 .+-. 0.31 mm (0.91-2.61 mm), and vertically 1.92 .+-. 0.29 mm (0.96-2.91 mm). The form was slightly vertically oval. Optic cup area averaged 0.72 .+-. 0.70 (0.00-3.41 mm2), mean horizontal cup diameter 0.83 .+-. 0.58 mm (0.00-2.08 mm) and mean vertical diameter 0.77 .+-. 0.55 mm (0.00-2.13 mm). The cup was significantly (P < 0.0001) larger in discs with steep "punched-out" cups (1.37 .+-. 0.62 mm2) compared to discs having cups with temporal flat slopes (0.59-0.39 mm2). Neuroretinal rim area ranged from 0.80 to 4.66 mm2 (mean 1.97 .+-. 0.50 mm2), and was significantly correlated (P < 0.00001) to the optic disc area. It was broadest in the inferior optic disc region (P < 0.001), followed by the superior, nasal and temporal (P < 0.001) regions. Horizontal cup/disc ratio (mean 0.39 .+-. 0.28, minimum 0.000, maximum 0.87) was larger in 426 (93.2%) optic discs than the vertical one (mean 0.34 .+-. 0.25, minimum 0.00, maximum 0.85). Concerning optic disc area, side differences of 0.10 mm2 or less were detected in 28%, of 0.2 mm2 or less in 46% and of 0.50 mm2 or less in 80% (cumulative frequencies). Concerning neuroretinal rim area, side differences of 0.10 mm2 or less were found in 31%, of 0.20 mm2 or less in 52% and of 0.50 mm2 or less in 84%. There were no significant correlations between these morphometric optic disc data and refraction, age, sex or side.