Changes in retinal vessel oxygen saturation using automated retinal oximetry in patients with significant carotid stenosis

Purpose: To evaluate the dynamics of changes in retinal oximetry parameters in patients with haemodynamically significant carotid stenosis Methods: In this case-control study we examined 74 eye artery pairs in 37 patients with significant carotid stenosis over 50 % using retinal oximetry. 14 eye artery pairs were excluded due to contraindications for oximetry or presenting carotid occlusion. From the remaining 60 eye artery pairs, 39 stenotic eye artery pairs were analyzed against the control group of 21 non-stenotic eye artery pairs. Results- Primary analysis of the data showed a trend to increased arterial saturation, decreased venular saturation and increased venular diameter. in all groups. The AV difference, the most sensitive parameter, however was only statistically significant for the 80 % stenosis patients. For each group, the cutoff value for the AV difference was chosen for calculation of the odds ratio (OR) of stenosis. Highest OR was found in the 80 % (9.0, p=0.007) with the threshold value of AV difference 38.72 %. Conclusion : The impact of carotid stenosis on retinal perfusion was confirmed with the highest predictive value for stenosis above 80 %. The relative decrease in the AV difference and normalisation of other parameters in stenoses over 90 % can be explained by collateral circulation via the external carotid artery. The relationship between the AV difference and degree of stenosis is non linear which points to the contribution of other mechanisms to reduced post-stenotic blood flow adaptation. This case-control study was conducted between 2021 and 2023 as a clinical trial approved by the Ethics Committee of the university hospital Olomouc, registered under ClinicalTrials.gov, ID: NCT06085612 All patients participated in the study willingly, providing informed consent in accordance with the Declaration of Helsinki. All methods used were carried out in accordance with relevant guideelines and regulations.