Abstract
Abstract: :
Purpose:Diffuse luminance flicker increases retinal vessel diameters in animals and humans, indicating the ability of the retina to adapt to different metabolic demands. The current study seeks to clarify whether flicker induced vasodilatation of retinal vessels is altered in glaucoma patients. Methods:31 patients with early stage glaucoma (washout for antiglaucoma medication) and 31 age and sex matched healthy volunteers were included in the study. Retinal vessel diameters were measured continuously with a Retinal Vessel Analyzer. During these measurements 3 episodes of square wave flicker stimulation (16, 32 and 64 seconds; 8 Hz) were applied through the illumination pathway of the Retinal Vessel Analyzer. Results:Flicker induced vasodilatation in retinal veins was significantly reduced in glaucoma patients as compared to healthy volunteers (ANOVA, p<0.01). In healthy volunteers retinal venous vessel diameters increased by 1.1±1.8% (16 sec, p<0.001), 2.0±2.6% (32 sec, p<0.001), 2.1±2.1% (64 sec, p<0.001) during the flicker stimulation periods, respectively. In glaucoma patients, venous vessel diameters increased by 0.2±1.7% (16 sec, p<0.6), 1.1±2.1% (32 sec, p<0.01) and 0.8±2.5% (64 sec, p<0.09). In retinal arteries, no significant difference in flicker response was noticed between the two groups (ANOVA, p<0.6). Conclusion:Flicker induced vasodilatation of retinal veins is significantly diminished in patients with glaucoma compared to healthy volunteers. This indicates that regulation of retinal vascular tone is impaired in patients with early glaucoma, independently of antiglaucoma medication.
Keywords: retina • signal transduction: pharmacology/physiology