What Causes The Vision To Move In Opposite Direction Of Head Movement?

I recently hit my head and damaged the 6 th cranial nerve on the left side resulting in constant double vision. Vtsual strabismus esotropic very apparent. Last week had a fesnel lens installed in glasses. I heard tech say it was the last 20 . Before I had to turn my eyes hard left to get a merge. Now can look straight ahead.Any movement of my head causes right image to move in opposite direction at same rate. If I have a prism ground in, why will it cause lookage or will it? I m 90 in a couple months. Loyal.