The Influence of Age, Gender, Refractive Error, and Optic Disc Area on the HRT Parameters in Normal Eyes

Purpose: To study the influence of age, gender, refractive error, and optic disc size on the optic disc parameters measured with the Heidelberg Retina Tomograph (HRT; software 2.01) in normal eyes. Methods: Ninety-two normal subjects (mean refractive errorSD: -0.151.64 D, range -6.63 to +3.38 D) were examined using HRT. The influence of age, refraction, and disc area on each parameter was analysed by multiple linear regression. Results: Large discs had large values of cup area, cup volume, rim area, cup to disc area ratio, and mean cup depth. Large discs had small values of rim to disc area ratio. However, rim volume, maximum cup depth, cup shape measure, height variation contour, mean retinal nerve fiber layer thickness, and retinal nerve fiber layer cross-sectional area were not related to disc area. Most parameters were independent of age or refractive error except for a few parameters. Age was weakly related to disc area. Refractive error was weakly associated with cup shape measure. Gender had no statistically significant influence on optic disc parameters. Conclusions: These results indicate that several optic disc parameters have better correlations with the optic disc area than age, gender, and refractive error. These differences must be considered in the evaluation of optic disc for glaucoma.