The study was done to analyse the peripheral extent of choroidal circulation using UWF indocyanine green angiography (ICGA) in healthy eyes.

UWF ICGA images of 55 eyes of 36 healthy subjects were captured using Optos California in this prospective observational study. Images were analysed to locate the peripheral extent of the visible choroidal circulation, and the boundary was marked in ImageJ (v1.52).

The mean area of the peripheral extent was estimated to be 893.2 mm2 (95% CI: 844.2 to 942.3 mm2). The mean distance (range) of this boundary from the optic nerve centre was 18.22 mm (95% CI: 14.0 to 23.14 mm). Multiple regression analysis with age, gender, axial length or ethnicity showed no relationship. There was excellent inter-grader reproducibility, with intraclass correlation coefficients of 0.95 (95% CI: 0.80 to 0.99, p<0.001) for distance and 0.99 for area measurements.

The study concluded that the peripheral choroidal boundary may be defined using UWF ICGA. Knowledge of the normal extent and its variability is essential to understand the impact of disease on the choroidal vasculature.