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 R² of regression models for the Extended zone was slightly higher than that for the Standard zone for both CRAE (R², 0.324 vs. 0.288) and CRVE (R², 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.