The authors present a post-hoc analysis using the publicly available data set from the Optic Neuritis Treatment Trial. The Cox proportional hazards regression models were used to assess for associations between clinical and radiological variables and the development of clinical definite multiple sclerosis (MS). This study used 388 participants from the original 457 participants of the Optic Neuritis Treatment Trial. Reasons for exclusion were definite MS at recruitment and misdiagnosis of optic neuritis. The model developed demonstrated improved prognostic accuracy for the development of definite MS over current standard practice using solely identification of brain lesions on MRI. This study was bound by the strict inclusion criteria set by the Optic Neuritis Treatment Trial, which the authors report as a limitation particularly due to the restricted age range. Whilst this model requires further testing in prospective studies, it has the potential to improve counselling and earlier treatment.