The effect of Fampyra on visual function following previous optic neuritis.

Optic neuritis is a condition where optic nerve inflammation occurs leading to reduced visual function. It is a common presenting episode of multiple sclerosis, and many patients with multiple sclerosis will have had optic neuritis through the course of their disease. Whilst high contrast visual acuity generally recovers well months following the event, there is evidence of under-recognised visual dysfunction in patients with previous optic neuritis, as well as Multiple Sclerosis, using other measures such as low contrast visual acuity and vision related quality of life measures. Fampyra is a potassium channel blocker which as been proven to improve walking speed in Multiple Sclerosis, as a symptomatic treatment. It's benefit is thought to be due to restoration of nerve conduction in unmyelinated nerves. Our plan is to test whether Fampyra can provide benefits on visual function in those patients with a previous episode of optic neuritis, and measures of visual dysfunction on screening investigations. The study will employ a randomised cross over placebo controlled study design, with 20 patients undergoing assessments around a 2 stage study, with Drug A and then Drug B given for a four week period, with a 2 week washout period. Visual assessments will be undertaken at baseline, and at 4 weeks on the study drug to look for change in function. Assessments will include low contrast visual acuity, vision related quality of life measure (NEI-VFQ25), visual evoked potentials (a electrophysiological marker of optic nerve conduction), and visual field testing.