Double vision needs a large amount of prism
I suffer from double vision and have a stick on prism from the hospital for my left eye that is 10 dp in strength. This was working well until recently when my eyes became blurry and I experienced double vision again. I had an eye test with Specsavers and my optician concluded that I needed a prism of 20dp. He prescribed glasses with a prism of 5dp in each lens (to make up to 10) and told me to wear the stick on prism on top. The trouble is, is that if I don't use the stick on lens with the glasses I still get double vision and headaches, and if I put the stick on prism on as well then it's uncomfortable to see and distorted. Is it usual practice to use a stick on prism on top of prism glasses?