Abstract
Purpose :
Fluorescein angiography (FA) remains the gold standard used to evaluate the morphology and leakage of retinal vasculature, but it requires an intravenous injection of fluorescein dye and a skilled photographer. OCT angiography (OCTA) is a newer noninvasive (contrast agent free) imaging technique developed to evaluate morphology of the retinal vasculature. This study evaluated whether retinal vascular density noted in murine eyes with diabetic retinopathy using FA is comparable to those observed using OCTA.
Methods :
Simultaneous FA and OCTA images were obtained, using custom build mouse retinal OCT/SLO system, from STZ (Streptozotocin)-induced diabetic mice 6 months after induction of diabetes. The acquired images (FA fundus and OCTA enface projections) were processed to obtain a better profile of the vascular parameters. At first, the Contrast-Limited Adaptive Histogram Equalization (CLAHE) was used to improve the background-vessel contrast. Then, a two-dimensional matched filter was applied by using a Gaussian kernel with two different standard deviation values to enhance both thick and thin vessels. Images of total areas of retina were obtained and analyzed using ImageJ software with the Vessel Analysis plugin to quantify the retinal vascular density of the entire imaged retina ~50deg FOV (total) on FA and OCTA.
Results :
Retinal vascular density of the total area on standard FA and OCTA images did not correlate significantly (N=14; correlation r=0.081, p value=0.783, using ANOVA regression). However, when analysis was performed on enhanced images using CLAHE and two-dimensional matched filter, vascular density on FA and OCTA images significantly correlated (N=14; correlation r=0.742, p value=0.002, using ANOVA regression).
Conclusions :
Retinal vascular density obtained using FA correlates well with retinal vascular density obtained using OCTA in murine eyes with diabetic retinopathy after application of Contrast-Limited Adaptive Histogram Equalization (CLAHE) and two-dimensional matched filter with Gaussian kernel. Vascular density on FA and OCTA was found to correlate better after image enhancement improved contrast of the fine retinal capillaries.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.