Flicker observation light induces diameter response in retinal arterioles: a clinical methodological study

Aim: To investigate diameter changes in retinal arterioles in response to flicker variations of the examination light. Methods: One randomised eye of five healthy subjects (mean age 33.8 (SD 1.6) years) was examined. The arterial diameter response to flicker light (12.5 Hz, 530 - 600 nm, duration 20 seconds) was automatically and continuously measured online three times by retinal vessel analyser (RVA) and once offline from flash images using the VesselMap program. Results: An arterial diameter response to flicker light was found both by RVA and by analysis of flash images (p< 0.001). The maximum induced dilation reached at the end of the flicker period was + 7.4% (SD 2.4%) in the RVA measurements and + 3.5% (0.8%) in the photographs (p = 0.01). In both techniques the vascular diameter overshot the baseline approximately 10 seconds. In the RVA measurements a minimum of -4.6% (1.9%) (p = 0.01) was measured 22 (4.7) seconds after the end of flicker exposure. Conclusion: Flicker evoked response for retinal arterioles was found both by RVA and by analysis of flash images. The authors believe that the method is suitable for the quantitative investigation of retinal vasosclerosis, especially in association with arteriosclerotic and hypertensive systemic disease.