Visualisation And Quantification Of Corneal Neovascularization Using Anterior Segment Optical Coherence Tomography Angiography - A Pilot Study

The immune privilege of the cornea is defined by its absence of blood and lymphatic vessels. Pathogenic stimuli may induce the development of corneal neovascularization (CNV), which is associated with a significant risk of rejection in the setting of penetrating keratoplasty. Objective evaluation and follow-up of CNV at the slit-lamp is difficult, whereas dye-based imaging techniques are associated with potential adverse effects, beside being invasive and  cumbersome to perform in a busy clinical routine. The purpose of this pilot study was to investigate the visualization and quantification of CNV using anterior segment optical coherence tomography angiography (AS-OCTA). 

Patients with manifest CNV were imaged with slit-lamp photography and VA-OCTA (+10 diopters lens mounted on Zeiss Plex Elite 9000) on the same day. Corneal slabs were segmented in structural OCT B-scans before OCTA signal detected capillaries were analyzed to measure vessel density and -area, as well as vessel arc length (using skeletonized vessel segmentation). OCTA signals between the air-epithelium interface and epithelium-bowman membrane interface on the one hand, and between the epithelium-bowman membrane interface and the endothelium interface on the other hand were analyzed separately to differentiate between superficial and deep CNV.

The analysis of twenty eyes of twenty patients showed that AS-OCTA allows detailed visualization and objective quantification of CNV using novel vascular parameters including capillary vessel density and -area as well as skeletonized vessel arc length. Furthermore, AS-OCTA enables the precise localization of the depth of corneal vascularization even in the presence of corneal scarring and opacification. CNV were better discriminated using AS-OCTA compared with slit-lamp photography in all eyes of this study.

AS-OCTA enables precise, non-invasive and objective visualization of corneal neovascularization, thereby demonstrating a precious tool in the longitudinal monitoring and therapeutic planning of a (lymp)-angioregressive preconditioning prior to keratoplasty in high-risk eyes.