This clinical trial is focused on studying the effects of a medication called clemastine fumarate in treating two conditions: multiple sclerosis and internuclear ophthalmoparesis. Multiple sclerosis is a disease that affects the brain and spinal cord, leading to a range of symptoms such as vision problems, balance issues, and muscle weakness. Internuclear ophthalmoparesis is a condition that affects eye movement, making it difficult for the eyes to move together properly.

The purpose of the study is to evaluate whether clemastine fumarate can help improve eye movement in patients with these conditions. The study will involve taking clemastine fumarate in the form of tablets, and some participants may receive a placebo, which looks like the medication but does not contain the active ingredient. Another medication, Fampyra, which is used to improve walking in people with multiple sclerosis, will also be part of the study. Participants will take the medication orally, meaning by mouth, over a period of time.

Throughout the study, participants will be monitored to see how their eye movements change over time. The study will last for several months, with follow-up periods to check if any improvements continue after the treatment ends. The goal is to see if clemastine fumarate can provide lasting benefits by helping to repair the protective covering of nerves, known as myelin, which is often damaged in multiple sclerosis. This process is called remyelination, and the study aims to determine if clemastine fumarate can support this process effectively.