White-to-white corneal diameter: normal values in healthy humans obtained with the Orbscan II topography system.
The corneal horizontal diameter (white-to-white) is abnormal in diseases like microcornea, relative anterior microphthalmos, and corneal dystrophies. Because normal values are described imprecisely in the literature, the purpose of this study was to reevaluate the horizontal corneal diameter as a scientific parameter. The horizontal corneal diameter was measured with the Orbscan II system in 370 right eyes and 373 left eyes of 390 healthy white subjects aged 10-80 years. There were 148 female subjects and 242 male subjects. Each measurement was repeated twice. Differences in gender, between right and left eyes, and age-related alterations were analyzed statistically. The average corneal diameter was 11.71 +/- 0.42 mm. The average corneal diameter was 11.77 +/- 0.37 mm in males compared with 11.64 +/- 0.47 mm in females. The resulting normal ranges were 11.04 to 12.50 for males and 10.70 to 12.58 mm for females. Differences in gender were not significant in the t test for independent samples (P = 0.071). There were no statistically significant differences between right and left eyes in the t test for dependent samples (P = 0.16). Corneal diameters decreased slightly with age. With the obtained normal values, more precise determination of microcornea and macrocornea will be possible in the future. The horizontal corneal diameter was not significantly greater in males than in females. Further studies are needed to show the reasons for the age-related decrease in measurements.