In vivo Noninvasive Imaging and Quantitative Analysis of Iris Vessels

Abstract

Objective: To quantify the iris vessels and its circadian rhythm in normal eyes.

Methods: Fifteen healthy subjects were enrolled in this retrospective, cross-sectional study. All subjects underwent optical coherence tomography angiography (OCTA) and indocyanine green angiography (ICGA) examinations, in which 3/15 completed ICGA and OCTA at the same visit. Upon visit, consecutive OCTA scans were then obtained at the time points of the hour 3:00, 6:00, 8:00, 10:00, 12:00, 14:00, 16:00, 18:00, 20:00, 22:00, and 24:00, respectively. Vessel area density (VAD) and vessel skeleton density (VSD) were used to quantitatively describe the OCTA images of the iris vessels.

Results: The VAD and VSD of the iris vessels had circadian rhythm with the highest values observed at about 18:00 h and lowest at 0:00 h; the overall values were relatively stable within the 24 h. The contour analysis suggested that the iris VAD and VSD were correlated with the changes in blood pressure and inversely correlated with the changes in the intraocular pressure.

Conclusions: OCTA can be used accurately for quantitative analysis of the iris vessels.

Keywords: In vivo noninvasive imaging; Iris vessels; Quantitative analysis.