Dynamic Color Doppler Imaging (dCDI): Effect of Flicker Stimulation on the Blood Flow Velocities in the Retrobulbar Arteries in Healthy Volunteers and Glaucoma Patients

Abstract

Purpose: : Several ocular diseases including glaucoma and diabetic retinopathy are associated with disturbed regulation of retinal and choroidal perfusion. This might be visualized by combining methods assessing ocular hemodynamics with procedures challenging regulation of retinal perfusion. In the present study a combination of flicker light stimulation with color Doppler imaging (CDI) is applied to healthy individuals and glaucoma patients.

Methods: : Color Doppler measurements were performed with a Siemens Elegra ultrasound set-up using an applicator type 7.5L40. The averaged mean blood flow velocity (TAMn) was evaluated. After a baseline measurement, the retina is stimulated by a 10 Hz flicker through the closed eye lids. CDI measurements were repeated 15s after flicker stimulation, as well as 60 and 120s after termination of the flicker light stimulation. In healthy volunteers or glaucoma patients either the central retinal artery (CRA) or the short posterior ciliary artery (SPCA) was assessed. For statistics an ANOVA model was applied.

Results: : In the CRA flicker light led to an increase of TAMn from 2.4±0.2 to 2.8±0.3cms-1 in healthy volunteers (n=17; P<0.05). Glaucoma patients had slightly reduced blood flow velocities at baseline and showed no significant increase of TAMn in presence of flicker (2.0±0.1 vs. 2.3±0.2cms-1; n=17; n.s.). In the SPCA of healthy controls flicker stimulation led to a rise of TAMn from 2.5±0.4 to 3.3±0.5cms-1 (n=9; P<0.05), while this effect was not detectable in glaucoma patients (2.2±0.2 vs. 2.5±0.5cms-1; n=20; n.s.). In the healthy controls the flicker induced hemodynamic changes were fully reversible in both vessels after 60 and 120s respectively.

Conclusions: : The data from the present study show an enhancing effect of retinal flicker stimulation on retrobulbar blood flow velocities in healthy volunteers in the CRA as well as in the SPCA. The flicker response in glaucoma patients deviates from that of healthy volunteers, which may indicate altered regulation of ocular perfusion in the glaucoma population of this study.

Keywords: blood supply • clinical laboratory testing • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)