oa Static and Dynamic Retinal Vessel Analyses in Patients with Stroke as Compared to Healthy Control Subjects

Background

Several risk factors for developing stroke have been described previously and the vast majority concerns the vascular system and its adjacent organs. The microcirculatory bed of the retina shares similar anatomical and physiological characteristics with the cerebral and coronary circulations. Therefore, structural changes in the retinal blood vessels can mirror cardio- and cerebrovascular events. In addition, dynamic response of vessel width during a stimulation with diffuse flicker light can be evaluated. In healthy subjects this stimulation leads to a vasodilation of retinal vessels, a phenomenon called neurovascular coupling. It has been shown that vascular pathologies like diabetes can reduce this flicker light evoked response.

The aim of the present study was to further substantiate the relevance of retinal analysis in stroke research. Retinal arterial and venous diameters were investigated in stroke patients and compared to the findings with healthy, age-matched control subjects. Effects of flicker light stimulation were compared between both groups.

Methods

18 patients suffering from recent stroke and 16 age-matched control subjects were included in the present study. In each subject review of current medication and medical history as well as physical and neurological examinations were performed. Static and dynamic vessel analyses were performed using the Retinal Vessel Analyser (RVA). RVA is a device for the evaluation of the retinal vascular system that allows precise measuring of the diameters of retinal arterioles and venules. In static vessel analysis diameter of all vessels entering the optic disc were evaluated. Central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE) and arterio-venous ratio (AVR) were calculated. In the dynamic analysis, a retinal arteriole and a retinal venule were examined before and after flicker light stimulation for 60 seconds. Flicker response, the relative change of vessel diameter due to flicker light stimulation, was calculated.

Results

CRAE was significant smaller in stroke patients as compared to the control group, whereas CRVE was comparable between the groups. AVR, therefore, was also significantly smaller in the stroke group. Dynamic vessel analysis also found reduced arteriolar diameters in stroke patients. Even though response to flicker light was smaller in stroke patients this difference did not reach level of significance. A moderate negative correlation could be shown for CRAE and the mean arterial pressure, as the latter was elevated in the patients group. No association could be found between CRVE and mean arterial pressure.

Conclusion

Patients who developed stroke show smaller retinal arterial diameters and tend to have a reduced flicker response. This decline in arterial diameter is probably explained by the more prevalent vascular risk factors like hypertension in this group of patients. The role of reduced retinal flicker response as a risk factor for stroke needs to be addressed in further studies. The data of our study is in good agreement with previous published data showing that smaller retinal arterial diameter is associated with an increased risk for developing stroke. Our study indicates that retinal analysis is a non-invasive and convenient tool that is relevant to study microvascular changes in stroke patients and at-risk individuals. This is of high relevance in Qatar's population due to the high prevalence of many risk factors – including diabetes, smoking, obesity, high cholesterol, hypertension and inactivity.