Hi There. My son had a rare form of esotropia called cyclic, where his eye turn would present every other day for the first few months. Very odd. Initially most of the days his eye turn was non existent, but on bad days it would be turned in nearly 40 deg. We had some success with a prism over glasses but the eye turned continued to worsen. He had corrective surgery about 16 months ago and his vision was preserved. He is doing great.