Tracing method in the assessment of retinal capillary blood flow velocity by fluorescein angiography with scanning laser ophthalmoscope

Purpose: To evaluate the feasibility of a new method (the tracing method) for measuring perifoveal capillary blood flow velocity (BFV). Methods: The BFV in the perifoveal capillaries was measured in 12 eyes of healthy subjects and 12 eves of patients with clinically significant macular edema (CSME) by fluorescein angiography using a scanning laser ophthalmoscope by either the tracing method or the conventional method. A randomized crossover design was employed to assign the subjects to each method. Results: The number of capillaries recognized by the tracing method in healthy subjects and in patients with CSME was significantly higher than that recognized with the conventional method (P = 0.0134 and P = 0.0108. respectively). The number of fluorescent dots detected by the tracing method in healthy subjects and in patients with CSME was also significantly higher than that detected with the conventional method (P = 0.0002 and P = 0.0137, respectively). Accurate detection of the movement of fluorescent dots and analysis of BFV were possible with the tracing method. The BFV varied within each perifoveal capillary and the mean BFV also varied according to capillary location in the macula. Conclusion: The new tracing method is useful for analyzing the retinal capillary BFV in healthy Subjects and in patients with CSME.