A new tool to assess retinal vessel caliber. Reliability and validity of measures and their relationship with cardiovascular risk

Objective: To analyze the reliability and validity of a semiautomated tool for assessing retinal vessel caliber and to describe the relationship of measures taken to cardiovascular risk and target organ damage. Methods: A total of 210 patients aged 34-75 years were selected with retinography. Retinal photographs were digitized, and superior and inferior temporal vessels were measured in an area 0.5-1 disk diameter from the optic disc with semiautomated software [arteriole/venule index (AVIx) calculator]. AVIx was also estimated. Vascular damage was assessed using carotid intima-media thickness and pulse wave velocity, cardiac damage using Cornell voltage-duration product, renal damage using the glomerular filtration rate and microalbuminuria, and cardiovascular risk with the Framingham score. Results: Interobserver intraclass correlation coefficient (ICC) ranged from 0.96 [95% confidence interval (CI) 0.94-0.97] to 0.99 (95% CI 0.98-0.99), and intraobserver ICC ranged from 0.97 (95% CI 0.94-0.98) to 0.99 (95% CI 0.99-0.99). In the Bland-Altman plot, the limit of interobserver agreement was -0.009 (0.066 to -0.086) in right AVIx and -0.001 (0.083 to -0.085) in left AVIx, whereas the limit of intraobserver agreement for overall AVIx was -0.005 (-0.057 to -0.047). Cardiovascular risk and albumin-creatinine ratio were higher in the first tertile of AVIx as compared with the other two (P<0.05). In multiple regression, AVIx and venule caliber, but not artery caliber, behaved as predictors of cardiovascular risk and microalbuminuria. Conclusion: This tool showed a high intraobserver and interobserver reliability, and results of the validity analysis agree with those from large studies in estimation of cardiovascular risk and evaluation of target organ damage.