Scanning laser tomography to evaluate optic discs of normal eyes.

PURPOSE: To investigate the effects of age, eye refraction, and disc area on topographic parameters of the optic nerve head in normal volunteers, using the Heidelberg Retina Tomograph.

METHODS: Seventy-seven eyes of 77 normal volunteers were examined by scanning laser tomography. The topographic parameters analyzed were disc area, cup area, cup/disc area ratio, rim area, cup volume, rim volume, mean cup depth, maximum cup depth, cup shape measure, height variation contour, mean retinal nerve fiber layer thickness (MnRNFLT), and retinal nerve fiber layer (RNFL) cross-section area. The effect of age, refraction, and disc area on each parameter was analyzed by the multiple linear regression model.

RESULTS: Significant declines in MnRNFLT and RNFL cross-section area were found with increasing age (P < .05). The mean cup depth and maximum cup depth were significantly deeper in myopic subjects (P < .05). Large discs had large cup area, cup/disc area ratio, rim area, cup volume, mean cup depth, cup shape measure (P < .01), and maximum cup depth (P < .05). The MnRNFLT was smaller in large discs (P < .01). Rim volume was unaffected by age, refraction, or disc area.

CONCLUSIONS: The age, refraction, and disc area were related to several optic disc parameters obtained by the Heidelberg Retina Tomograph. Because of these relationships, care should be taken to analyze the appearance of the optic disc on the basis of these parameters in patients with glaucoma or other diseases. Rim volume appears to be a good parameter for evaluating the optic disc without considering age, refraction, or disc area.