Is it possible to have eye muscle transplants to fix my crossed eyes?

I had strabismus surgery (procedure to straighten crossed eyes) on both of my eyes. The results were great for the first 18 months. In the last several months, my eyes have been returning to the state they were once in prior to the surgery. I don't think it's viable to do the surgery every two years. I've read about eye transplants but most sources describe only corneal transplantation. Can you tell me if there are eye muscle transplants?

There are no eye muscle transplants available. Some patients do have a recurrence and need reoperations but that should not happen every two years. I would discuss with your surgeon.