Vasculature analysis by anterior segment OCT angiography in light- and dark-colored eyes

Abstract

Purpose : OCT angiography (OCT-A) has expanded imaging of retinal and choroidal perfusion. Here we used OCT-A for the anterior segment. This study aimed at evaluating differences in imaging iridal vasculature of dark-colored eyes vs. light-colored eyes with anterior segment OCT angiography (AS-OCT-A), and at defining anterior segment vasculature tracked by AS-OCT-A regarding inflammation and perfusion features.

Methods : For AS-OCTA, a modified PLEX Elite 9000 (Carl Zeiss Meditec, Dublin, CA, USA) was used, featuring swept-source OCT with a wavelength of 1050 nm and an A-scan repetition rate of 100 kHz. One of two add-on lenses (+10dpt and +20dpt) were used in the optical path. The angiography 6x6 mm scan (in terms of retinal field-of-view) was used. Because of the additional lens and divergent geometry, the actual field of view was larger than 6mm. A cohort of healthy participants were examined, stratified by iris color and analyzed regarding vessel density and image quality (SNR). In a consecutive set, we imaged eyes with pathologies of the iris and compared imaging quality and lesion characteristics by two readers.

Results : Fifteen light-colored eyes (7m, 8f; age 35.3±7.1) and 15 dark-colored eyes (7m, 8f; age 34.5±6.2) of 30 healthy participants were included for the first analysis. Light-colored eyes revealed a better visibility (mean intensity index of 1.5) of the iris blood vessels than dark-colored eyes. Dark-colored eyes showed more shadowing and decorrelation artifacts. The use of corneal lubricants significantly improves imaging quality (SNR) in all cases. Moreover, additional fifteen eyes with pathology of the iris (5 naevi [2m, 3f], 5 iritis [2m, 3f], 5 rubeotic iris [3m, 2f]) were analyzed. Rarefied vessels, neovascularizations and inflammative hyperperfusion were scrutinized based on our normative iris analyses. Destinction was primarily derived from vascular diameter. Iris color however did not influence sensitivity of findings.

Conclusions : The findings contribute to a better understanding of AS-OCT used for the visualization of blood vessels of the iris. Corneal status is a relevant factor for the quality of images and perfusion analysis by AS-OCT. Our results show that this innovative tool can readily be used for the diagnosis and monitoring in the context of diseases that affect blood flow of the iris vasculature.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.