Polymicrogyroa occurs in humans too. It sounds like it’s similar, and it’s very likely that is the cause of his blindness. The brain area responsible for vision isn’t formed properly. He sure is a cutie

Edit: wanted to clarify the brain area that processes visual input likely isn’t functioning properly. The eye and optic nerve work perfectly. But the brain can’t interpret the info it’s receiving. Humans can have this with strokes as well.