Incidence of Optic Neuritis among Omani Patients with Multiple Sclerosis at the Sultan Qaboos University Hospital, Muscat, Oman.

Objectives: Multiple sclerosis (MS) is a chronic, multifaceted, heterogeneous autoimmune disease, with optic neuritis (ON) being a common early manifestation among those with MS. This study aimed to estimate the incidence of ON among Omani patients with MS. Methods: This retrospective cross-sectional study included all Omani patients diagnosed with MS at the Sultan Qaboos University Hospital, Muscat, Oman, between January 1991 and December 2019. The data were collected from the neurology registry and electronic medical records and analysed descriptively using univariant and multivariant statistical techniques. Results: Out of the 185 patients diagnosed with MS during the study period, 170 were included in the analysis. The male-to-female ratio was 1:2 and the mean age was 28 years. The incidence of ON in the population was 28.8%, with 83.7% of ON patients presenting with relapse-remitting MS (RRMS). Overall, 28.6% of patients presented with O N as an initial manifestation of MS, whereas 42.8% developed ON at a later stage. Most patients (49.4%) were from higher-latitude regions of Oman such as Muscat and Al Batinah. Conclusions: The incidence of both MS and ON increased over the study period. While the overall incidence was low in comparison with Western data, it was similar to the rates reported elsewhere in the Arabian Peninsula. Overall, ON was the most common manifestation of MS in the cohort, with younger female patients more frequently presenting with both MS and ON. A significant association was found between the RRMS subtype and ON presentation.