To analyze microvascular and structural changes in patients with multiple sclerosis (MS) and to correlate with optic nerve involvement and disease progression. 

MS is an inflammatory demyelinating disease of the central nervous system. Retrobulbar Optic neuritis (ON) is common in MS. Optical Coherence Tomography (OCT) is non invasive ocular imaging technique useful to investigate optic nerve involvement during MS. OCT Angiography (OCT-A) is a new non-invasive imaging technique used for investigating the retinal and chroidal microvasculature that can also be a biomarker in MS diagnosis and prognosis. 

A case-control study was performed including Tunisian patients diagnosed with MS according to 2017 McDonald criteria, and age and gender matched healthy controls (HC). All participants underwent swept source (SS)-OCT and macular 3X3 OCT angiography (OCT-A). Clinical history, Expanded Disability Status Scale (EDSS), disease duration and Multiple Sclerosis Severity Score (MSSS) were collected.

A total of 160 MS eyes with and without history of ON and 64 age- and gender healthy eyes were analyzed. Among 160 eyes with MS, 69 had a history of ON. We found a significant reduction in all OCT retinal thicknesses and superficial OCT-A macular vascular density in comparison to control eyes. On the other hand, we found a significant thinner retinal nerve fiber layer and ganglion cell complex thickness in eyes with ON but without significant difference in vascular flow density. Finally, we found an inverse correlation between OCT parameters and MSSS and EDSS in both groups with or without ON.

Retinal changes occur early during MS even in eyes without ON. OCT  coupled with OCT-A are good tools in staging prognosis and monitoring disease progression.