Abstract
Purpose: :
To study regional differences in retinal blood flow velocity in different areas of the macula in healthy subjects and patients with diabetes mellitus. We used the Retinal Function Imager (RFI, Optical Imaging Ltd., Rehovot, Israel), a new, non-invasive diagnostic approach for measuring blood flow velocity.
Methods: :
Fifty one eyes of 31 healthy subjects and twenty three eyes of 14 patients with early DM without any signs of retinopathy were enrolled to this study. The RFI was used to image the macula using 20 degrees area analyzing blood flow velocity in multiple vascular segments simultaneously. The macular scans were divided into halves vertically and horizontally and the average velocity of segments in each hemi-retina was computed. Differences in sectorial average velocities were assessed by Students' t-test analysis.
Results: :
Arterial velocity in the nasal hemi-retina was higher compared to the temporal region in the healthy group (4.38 vs 3.88 mm/sec, p=0.007). A similar difference was evident in the DM group (5.07 vs 3.94 mm/sec for nasal and temporal regions, respectively, p=0.003). However, venous velocity that was higher in the nasal region in healthy subjects (3.07 vs 2.80 mm/sec, p=0.01) did not differ regionally in veins of DM patients. Dividing the data attitudinally to superior and inferior halves did not show any differences in both groups.
Conclusions: :
In both groups, a higher velocity was found in nasal arteries compared to arteries in the temporal half of the macula. This regional difference can be a result of more proximal location manifesting in higher pressure and velocity. The same phenomenon was found in the veins of the healthy group but not in the diabetic group, which may reflect the higher inter-subject variability in the diabetic group related to differences in duration of the diabetic disease. Information about regional differences in velocity, as shown here, might serve as an additional diagnostic tool especially when local retinal disease exists.
Keywords: blood supply • imaging/image analysis: clinical • macula/fovea