Abstract
Purpose :
To use Adaptive Optics Scanning Laser Ophthalmoscopy (AOSLO) XT images, which capture moving red blood cells, to find central and peripheral retinal blood velocity with manual and semi-automated methods.
Methods :
In XT images, a composite of horizontal scans is analyzed over time, where retinal blood velocity is quantified as the time an erythrocyte takes to cross the scanning beam (the streak angles). Combining the streak angle with vessel angles gives an estimate of velocity. Using a manual method, 6 peripheral and 6 central erythrocyte streaks were measured with ImageJ software. In the automated method, 10-28 peripheral and 10-28 central streaks were manually circled, and angles were determined by the Radon transform. In total, there were 21 XT frames from 7 eyes (4 healthy, 2 diabetic without retinopathy (DM no DR), 1 with non-proliferative retinopathy (NPDR)) with vessel diameters ranging from 120-210μm. Each vessel was divided into thirds, and the central and combined peripheral blood velocities were calculated and compared per frame.
Results :
In all frames, central velocity was significantly greater than peripheral using the manual method (p<0.0001) and in all frames but one using the Radon method (p<0.0001). The ratio of peripheral to central velocity using the manual method was 0.66±0.09 vs 0.75±0.12 with the Radon method. The peripheral and central velocities were 51±5.2 mm/sec and 70±11 mm/sec for the 4 healthy eyes (150-180μm) and 53±5.3 mm/sec and 75±9.4 mm/sec for the 2 DM no DR eyes (120, 210μm). For the severe NPDR eye (200μm), the profile was flatter with the peripheral and central velocities at 54±8.4 mm/sec and 62±4.0 mm/sec, respectively.
Conclusions :
Both the manual and Radon methods showed parabolic blood velocity profiles in retinal AOSLO XT images, with the manual technique showing a greater difference. In this pilot data set, central velocity seems higher in DM no DR eyes and lower in NPDR eyes compared to healthy eyes, while being greater than peripheral velocity in all eyes. These measurements may offer insights into the impact of DM on retinal perfusion given the DM-induced changes in viscosity, and red cell flexibility.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.