REPRODUCIBILITY OF RETINAL AND OPTIC-NERVE HEAD BLOOD-FLOW MEASUREMENTS WITH SCANNING LASER-DOPPLER FLOWMETRY

Purpose: To evaluate the interobserver variability and the reproducibi lity of retinal and optic nerve head capillary blood flow measurements performed with a new noninvasive equipment, the scanning laser Dopple r flowmeter (Heidelberg Engineering, Heidelberg, Germany). Methods: Bl ood flow measurements were performed during three independent sessions in six patients with glaucoma and five normal subjects using the scan ning laser Doppler flowmeter (SLDF), which allows the visualization of perfused capillaries and vessels of the retina and optic nerve head a nd enables the quantification of capillary blood volume, flow, and vel ocity in any selected area of the perfusion map. To evaluate the inter observer variability in selecting the areas in the perfusion map to be measured, three observers tried to locate the same areas in the perfu sion map of images obtained during the first session. To evaluate the reproducibility of the measurements, the observers measured correspond ent areas in the peripapillary retina and in the optic nerve head of i mages from the three sessions. Areas of different sizes (10 x 10 pixel s and 4 x 4 pixels) were measured. Results: The agreement between read ings performed by the three observers was very good, with the reliabil ity coefficient for the various parameters varying from 0.90 to 0.98. The reproducibility of retinal and lamina cribrosa measurements with t he 10 x 10 pixel square target was good (reliability coefficient for t he different parameters ranging from 0.70 to 0.85) and much better tha n the reproducibility of the 4 x 4 pixel target. The measurements perf ormed in the neuroretinal rim area also had poor reproducibility. The measurements from the patients with glaucoma tended to be more reprodu cible than those from normal subjects. Conclusions: The SLDF allows re producible blood perfusion measurements of retinal and lamina cribrosa areas when a target square of 10 x 10 pixels is used.