Precise Measurement of Retinal Vascular Bed Area and Density on Ultra-wide Fluorescein Angiography in Normal Subjects.

PURPOSE: To characterize and quantify the total retinal vascular bed area (RVBA) and vascular density (VD) in normal eyes using stereographically corrected ultra-wide-field (UWF) fluorescein angiography (FA).

DESIGN: Cross-sectional study.

METHODS: Fifty-nine eyes of 31 normal subjects with no evidence of ocular disease underwent FA using the Optos 200Tx (Optos plc, Dunfermline, United Kingdom). Central and peripheral-steered FA images were montaged and stereographically projected. The early-phase FA was used to extract the retinal vasculature as a binary mask. Two independent, masked reading center-certified graders delineated the peripheral edge of the total retinal area (TRA) on a middle-phase frame. The RVBA and TRA were computed automatically in mm2 using software provided by the manufacturer. The VD was calculated by dividing RVBA by TRA.

RESULTS: The mean RVBA was 42.3 ± 14.8 mm2 for the entire retina, with no difference between male and female subjects (P = .439) or between right and left eyes (P = .407). The mean VD was 4.3% ± 1.4% for the entire retina, with no difference based on sex (P = .629) or laterality (P = .426). A negative correlation was observed between age and both RVBA and VD (RVBA: R = -0.6, P < .001; VD: R = -0.52, P < .001). Pairwise comparisons showed that subjects aged >65 years had smaller RVBA and VD than those younger than 50 years for the entire retina and in all quadrants.

CONCLUSIONS: RVBA and VD can be extracted from UWF FA images using automated processing techniques and may provide a reliable alternative to measures such as nonperfusion area.