Prisms

I live in rural France and have ocular myasthenia gravis. My eyes are getting worse and the ophthalmologist here cannot get the prisms right. I'm wearing a pair of glasses which are now 4 years old. Getting to see a neurologist is very difficult and I'm not on any medication but know I need to see someone. Last time in saw a neurologist in France, he had never even seen someone before with myasthenia! At the moment I just don't know what to do.