Association of retinal vessel caliber to optic disc and cup diameters.

PURPOSE To investigate whether optic disc size is related to retinal venule and arteriole diameters. METHODS The population of Beaver Dam, Wisconsin, aged 43 to 86 years were invited to participate in a baseline examination from 1988 to 1990. During this examination, photographs, centered on the optic discs, were taken after pupil dilation. Optic discs and cups were measured from stereoscopic photographs, whereas retinal vessel measurements were taken from a single digitized photograph. Central retinal vein and central retinal arterial equivalents were subsequently calculated. Data for 3887 right eyes are included in the analyses. RESULTS Narrower retinal venules and arterioles were found in the smaller optic discs controlling for optic cup diameter as well as age, systolic and diastolic blood pressure, refraction, and sex. Central retinal artery equivalents ranged from 156.04 +/- 16.82 microm in the smallest optic disc category to 165.93 +/- 15.17 microm in the larger disc category (P < 0.001). Central retinal vein equivalents ranged from 228.93 +/- 21.26 microm in the smallest to 243.18 +/- 22.32 microm in the larger disc categories (P < 0.001). The significant reduction in retinal vessel diameters was only apparent for the smallest optic disc sizes. A reduction in retinal vessel diameters was less consistent and not significant for small optic cup sizes. CONCLUSIONS Smallest optic discs were associated with smaller central retinal artery and central retinal vein diameters. This anatomic relationship may be useful as an additional associated indicator for nonarteritic anterior ischemic optic neuropathy as well as for retinal vascular events.