A new method to measure peripheral retinal vascular caliber over an extended area

Abstract

Objective: To describe a new computer-assisted method to measure retinal vascular caliber over an extended area of the fundus. Methods: Retinal photographs taken from participants of the Singapore Malay Eye Study (n = 3280) were used for this study. Retinal vascular caliber was measured and summarized as central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) using a new semi-automated computer-based program. Measurements were made at the Standard zone (from 0.5 to 1.0 disk diameter) and an Extended zone (from 0.5 to 2.0 disk diameter). Results: Reliability of retinal vascular caliber measurement was high for the new Extended zone (intraclass correlation coefficients >0.90). Associations of CRAE with blood pressure were identical between the Extended and Standard zones (linear regression coefficient -2.53 vs. -2.61, z-test between the two measurements, p = 0.394). Associations of CRAE and CRVE with other cardiovascular risk factors were similar between measurements in the two zones. The R 2 of regression models for the Extended zone was slightly higher than that for the Standard zone for both CRAE (R 2, 0.324 vs. 0.288) and CRVE (R 2, 0.325 vs. 0.265). Conclusions: The new measures from Extended zone are comparable with the previous measures, and also more representative of retinal vascular caliber. © 2010 John Wiley & Sons Ltd.