Abstract
Abstract: :
Purpose: To evaluate the relationship between optic cup (and disc) diameter and retinal vessel caliber. Methods: The population of Beaver Dam, WI aged 43–84 years in 1988 was invited to participate in a baseline examination from 1988–1990. A standardized exam and interview was administered during which refraction was measured and photographs of the retina were obtained. Optic cup and disc measurements were obtained from stereoscopic photographs of ETDRS field 1 (centered on the optic disc). Horizontal and vertical diameters were measured using a template of graded circles. Computer–assisted grading was done from the digitized Field 1 photo to determine central retinal artery (CRAE) and central retinal venule equivalents (CRVE). These measures were then used to calculate the arteriole–to–venule ratio (AVR). Analysis was done on 4039 right eyes from the baseline examination with optic nerve head and retinal vessel measurements that were free from signs of open–angle glaucoma. Results: After adjustment for age and refraction, persons with the smallest cup measurements had significantly smaller CRAE measurements. The 34 persons with no measurable vertical cup had an adjusted mean CRAE of 160.14 microns, while the 141 with next smallest cup measurement (0.015 inches) had an adjusted mean CRAE of 162.97 microns and the remainder of persons (N=3819, cup >= 0.031 inches) had a mean CRAE of 164.92 microns (p–value for trend=0.02). There were no significant differences in mean CRAE among those with cup measurements >= 0.031 inches. These relationships were also true for horizontal cup measurements as well as disc measurements. A similar pattern was found for CRVE, but not for the ratio (AVR). Conclusions: Persons with very small optic cups have smaller retinal arterioles and venules. These relationships remain after adjusting for refractive error. This is consistent with the notion that persons with small cups have a more constricted space for vessels entering the eye, which may be manifested in smaller CRAE and CRVE measures.
Keywords: blood supply • optic disc