Retinal vessel oxygen saturation is affected in multiple sclerosis and optic neuritis

BACKGROUND: Structural and metabolic changes in the retina may serve as biomarkers in central nervous system disease. Optical coherence tomography studies have shown structural changes in the retina of patients with multiple sclerosis (MS). We aimed to find whether retinal oxygen levels are affected in MS patients and/or eyes with optic neuritis when compared with healthy subjects or unaffected fellow eyes. METHODS: We compared oxygen saturation in retinal blood vessels in MS patients and healthy controls. Oxygen saturation of haemoglobin was measured in retinal blood vessels with a spectrophotometric non-invasive retinal oximeter. Twenty-nine patients with MS, of whom 12 had a history of optic neuritis, were examined. Data were compared between the affected and non-affected optic neuritis eyes and 29 healthy individuals in a case-control study. RESULTS: Retinal vessel oxygen saturation was significantly increased in MS patients compared with healthy controls. Arteriolar saturation was 96.2% ± 3.6% in the MS cohort (mean ± SD, n = 29) and 93.8% ± 3.7% (n = 29, p = 0.017) in the healthy cohort. Venular saturation was 64.2% ± 5.0% in the MS cohort (n = 29) and 59.3% ± 6.0% (n = 29, p = 0.001) in the healthy cohort. Oxygen saturation in retinal venules in MS patients was higher in eyes with known optic neuritis (65.1% ± 4.1%; mean ± SD, n = 10) than in unaffected fellow eyes (62.3% ± 6.3%, p = 0.049). CONCLUSIONS: The results suggest that retinal oxygen metabolism is affected in MS patients and optic neuritis. Non-invasive retinal oxygen imaging may be an objective biomarker in MS and optic neuritis and useful in the study of its pathophysiology. Further studies are needed to confirm and expand these findings.