Multiple sclerosis (MS) is an inflammatory, demyelinating and neurodegenerative disease of the central nervous system (CNS). Visual dysfunction is one of the most common symptoms of MS. Optic neuritis (ON), typically demyelinating, is one of the most frequent manifestations of MS. It can be inaugural in 30% of MS cases [1]. Patients who did not exhibit ON during the disease course would most likely have subclinical lesions in the visual pathways, as previously demonstrated in postmortem studies [2]. At the clinically isolated syndrome stage, around one-third of patients present asymptomatic optic nerve lesions [3]. At clinically definite MS stage, around half of patients have asymptomatic optic nerve lesions [4]. Moreover, in patients with a radiologically isolated syndrome, the functional deficit in the visual afferent pathway which was evaluated via multifocal visual evoked potentials (VEP) was in line with the structural loss in the retina observed in recent studies using optical coherence tomography (OCT) [5]. In fact, OCT is a rapid noninvasive imaging technique allowing the study of anterior visual pathways. For some authors, the retina is considered as a window to the optic nerve, while it is considered by others as a window to the CNS as it is an anatomically and developmentally extension of it [6]. Giving its easy accessibility to optical imaging, OCT would represent a reliable biomarker for MS pathology and severity assessment. It allows the monitoring of visual relapses and the assessment of axonal loss within the optic nerve leading to thinning of the retinal nerve fiber layer (RNFL) and the common ganglion cell and inner plexiform layer (GCIPL) [7]. According to these OCT findings, the visual pathway is now recognized as a structure-function correlation model suitable to study MS pathophysiology and treatment efficiency. Alterations in the architecture of the retinal layers have been well described in MS patients, however little is reported about retinal microvascular changes. Nonetheless, several studies have described cerebral vascular changes in MS patients [8], [9]. Thus, the study of retinal micro-vascularization in MS would reveal abnormalities similar to those found in the brain [10]. OCT-angiography (OCT-A) is a novel noninvasive imaging technique that allows rapid and accurate exploration of the retinal blood vessel networks. Initial OCT-A studies in MS are recent and have identified reduced retinal vascular densities in relatively small cohorts of MS patients [11], [12], [13]. In this context, we aimed to assess structural and microvascular retinal changes in patients with MS with and without ON and to correlate the findings with visual function and MS disability.