Background: Large vessel carotid stenosis represent significant cause of ischaemic stroke. Indication for surgical revascularisation treatment relies on severity stenosis and clinical symptoms. Mild clinical symptoms such as transient ischemic attack, amaurosis fugax or minor stroke preceded large strokes in only 15% of cases.

Aim: The aim of this prospective study is to evaluate whether retinal perfusion is impacted in significant carotid stenosis. Automated retinal oximetry could be used to better evaluate perfusion in post-stenotic basin. The investigators presume the more stenotic blood vessel, the more reduced retinal perfusion is resulting in adaptive changes such as higher arteriovenous saturation difference due to greater oxygen extraction. This could help broaden the indication spectrum for revascularisation treatment for carotid stenosis.

Methods: The investigators plan to enroll 50 patients a year with significant carotid stenosis and cross-examine them with retinal oximetry. Study group will provide both stenotic vessels and non-stenotic vessels forming the control group. Patients with significant carotid stenosis will undergo an MRI examination to determine the presence of asymptomatic recent ischaemic lesions in the stenotic basin, and the correlation to oximetry parameters.

Statistics: Correlation between the severity of stenosis and retinal oximetry parameters will be compared to the control group of non-stenotic sides with threshold of 70%, respectively 80% and 90% stenosis. Data will be statistically evaluated at the 5% level of statistical significance. Results will be then reevaluated with emphasis on MRI findings in the carotid basin.

Conclusion: This prospective case control study protocol wil be used to launch a trial assessing the relationship between significant carotid stenosis and retinal perfusion measured via automated retinal oximetry.

Inclusion Criteria:

Study population will include patients examined in ultrasound laboratory in Neurology department of University Hospital Olomouc, regardless of incidental finding of stenosis, examination due to acute symptoms or regular checkup of known stenosis.

Exclusion Criteria:

• patients unable undergo ophthalmological examination properly, especially on automated retinal oximetry.

Study population will include patients examined in Neurosonological laboratory in Neurology department of University Hospital Olomouc,