Optic disc, cup and neuroretinal rim size, configuration and correlations in normal eyes

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 less than 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 less than 0.00001) to the optic disc area. It was broadest in the inferior optic disc region (P less than 0.001), followed by the superior, nasal and temporal (P less than 0.001) regions. Horizontal cup/disc ratio (mean 0.39 +/- 0.28, minimum 0.00, 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%.(ABSTRACT TRUNCATED AT 250 WORDS)