Laser Scanning Tomography of Optic Discs of the Normal Japanese Population in a Population-based Setting

Objective: To evaluate the optic disc characteristics using the Heidelberg retina tomograph (HRT) II in a large sample of normal Japanese subjects. Design: Cross-sectional study. Participants: A total of 3576 eyes of 2036 normal subjects, with good-quality HRT II images, of 6042 eyes of 3021 subjects aged 40 years or more who participated in the Tajimi Study, a population-based eye study in Japan. Methods: Optic disc parameters were obtained using HRT II, and the association of gender, age, height, weight, blood pressure, ocular perfusion pressure, refraction, intraocular pressure (IOP), central corneal thickness (CCI), and disc size on HRT parameters was assessed using simple and multiple regression analyses. Main Outcome Measures: HRT parameters, including disc area, cup area, rim area, cup-to-disc area ratio, cup volume, rim volume, mean cup depth, maximum cup depth, height variation contour, cup shape measure, mean retinal nerve fiber layer (RNFL) thickness, and RNFL cross-sectional area, and the crude and partial correlations of the potential confounders with the HRT parameters. Results: Disc area, cup-to-disc area ratio, and rim area averaged 2.06 +/- 0.41 mm(2) (mean +/- standard deviation), 0.23 +/- 0.13, and 1.55 +/- 0.29 mm(2), respectively. All HRT parameters were strongly or moderately correlated between right and left eyes (Pearson's correlation coefficients = 0.45-0.83, P<0.001). Absolute inter-eye differences in several HRT parameters were positively correlated with disc area (P<0.05). Multiple regression analyses adjusting for the confounders showed weak but significant correlations of height, refractive error, IOP, and CCT with several HRT parameters (partial correlation coefficient (absolute value) = 0.04-0.16, P<0.05), and moderate or weak but significant correlations of disc: area with all HRT parameters (partial correlation coefficient [absolute value] = 0.05-0.73, P<0.05). Gender, weight, blood pressure, and ocular perfusion pressure did not significantly correlate with HRT parameters. Conclusions: This report presents reference data of normality for the HRT parameters based on a large sample of normal Japanese subjects. There were small but significant influences of height, refractive error, IOP, and CCT on several HRT parameters. Many HRT parameters were moderately or weakly affected by disc size. Financial Disclosure(s): Proprietary or commercial disclosure may be found after the references. Ophthalmology 2009;116:223-230 (C) 2009 by the American Academy of Ophthalmology.