Scanning laser ophthalmoscopy-based evaluation of epipapillary velocities:Method and physiologic variability

Purpose: Scanning laser ophthalmoscopy is capable of producing high-resolut ion fluorescein angiograms. Measurements of capillary blood velocities in t he fovea are well established. In this study, we used an identical techniqu e to measure particle velocities in the superficial layers of the optic ner ve head. We compared these data with simultaneous velocity measurements in the retinal and macular vasculature. Methods: Fluorescein angiograms were p erformed in 30 subjects (12 men, 18 women; mean age, 26 years; standard dev iation [SD], 3 years). Off;line, the velocities of hypofluorescent particle s through the microvasculature of epipapillary and macular vessels were mea sured by image-processing techniques. We also assessed the arteriovenous pa ssage (AW) time of the fluorescein dye front. Results: Epipapillary blood v elocities ranged from 2.7 to 6.5 mm/sec (mean, 4.0 mm/sec; SD, 0.99 mm/sec) and differed significantly from macular capillary blood velocities (MCBVs) , which ranged from 1.67 to 3.31 mm/sec (mean, 2.53 mm/sec; SD, 0.34 mm/sec ). The AVP time in all subjects was 1.74 +/- 0.5 sec (mean +/- SD) and corr elated with the MCBV (P < 0.05, r = -0.46). Epipapillary blood velocities s howed no correlation with either AVP time or MCBV. Conclusions: The scannin g laser methodology, adapted to objectively assess velocities in the epipap illary vasculature, shows that these measurements are neither correlated wi th velocities in the perifoveal network, nor inversely correlated with over all retinal transit time. Epipapillary blood velocities were found to be su bstantially higher than those measured in macular capillaries. This result might be explained by the different anatomy of epipapillary vessels compare d with macular capillaries. (Surv Ophthalmol 44 [Suppl 1]:S3-S9, 1999. (C) 1999 by Elsevier Science Inc. All rights reserved.).