Anterior segment optical coherence tomography angiography fo
A Study was conducted to compare the anterior segment optical coherence tomography angiography (AS-OCTA) systems in delineating normal iris vessels and iris neovascularisation (NVI) in eyes with pigmented irides.

10 consecutive patients with normal pigmented iris, had AS-OCTA scans with a described illumination technique, before using the same protocol in five eyes with NVI (clinical stages 1–3). All scans were sequentially performed using a spectral-domain OCTA (SD-OCTA), and a swept-source OCTA (SS-OCTA, Plex Elite 9000). Images were graded by two masked observers for visibility, artefacts and NVI characteristics. The main outcome measure was iris vessel density measurements comparing SS-OCTA and SD-OCTA systems.

--The median age of subjects was 28 years, and 50% were female. The paired mean difference of iris vessel density measurements was 11.7, SS-OCTA detecting more vessels than SD-OCTA.

--The inter-rater reliability for artefact score (K=0.799) and visibility score (K=0.722) were substantial.

--Both AS-OCTA systems were able to detect NVI vessels with a fair agreement (K=0.588), with clearer NVI characteristics in stage 1/2 compared to stage 3 NVI (mean difference NVI score: 2.7±0.4).

In conclusion, in normal pigmented irides, SS-OCTA was better able to define vessels of iris than in SD-OCTA. The atypical configuration or location of the AS-OCTA systems highlighted NVI features, while additional enhancements to allow for more precise objective serial quantification for usage in clinics have been required.