A New Method to Measure Peripheral Retinal Vascular Caliber over an Extended Area

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 sum mat vied as central retinal artery equivalent (CRAE) and central retinal vet equivalent (CRVE) using a new semi-automated computer-based program Measurements were made at the Standard zone (nom 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 lot 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