High Reproducibility of Retinal Blood Flow Velocity Measurements Using the Retinal Function Imager

Abstract

Purpose: : To assess the intra-session and inter-session reproducibility of blood flow velocity measurements in the perifoveal vessels using the Retinal Function Imager (RFI).

Methods: : Twenty six eyes of 20 healthy subjects free from eye disease and with no history of ocular trauma were recruited for this study. All patients were imaged by the RFI (Optical Imaging, Ltd). with analysis of blood flow velocity of secondary and tertiary branches of arteries and veins. The RFI scan was repeated three times for every measured region. Intra-session variability was assessed by the coefficient of variance (standard deviation divided by the mean) of all measured segments between each repeated scan. Five eyes of 5 subjects were re-imaged on a different occasion, days to months apart from the first measurement. Inter-variability was calculated using intraclass correlation.

Results: : The average venous velocity was 3.3 ± 0.6 mm/sec; the average arterial velocity was 4.3 ± 0.9 mm/sec. On average, 15.9 ± 5.8 arterial segments and 16.2 ± 5.4 venous segments were measured in each eye. The average coefficient of variance between measurements in the same day was 8.5 ± 4.9 % for all vessels; 8.5 ± 5.2 % for venules and 8.4 ± 4.8 % for arterioles. When comparing the measurements on different days on the same subjects the average interclass correlation was r = 0.964.

Conclusions: : The RFI showed low intra-session and intersession variability in a group of healthy subjects. These highly reproducible measurements might serve as an important tool for assessing both physiological and pathological processes affecting retinal blood flow velocity.

Keywords: imaging/image analysis: clinical