In my thirty year career as a special education teacher, I have seen children with specific visual conditions and disabilities benefit greatly from the proper eye exercises, prescribed by a doctor and carried out by a trained professional. Home exercises were also part of the program.
From my experience, although limited, I would liken it to physical therapy. Anyone can exercise their shoulder, but you want a pt who knows exactly what exercises to do for your specific type of shoulder problem.
I would hazard a guess that general eye exercises not prescribed by a physician would be rather pointless, but it's just a guess based on my experience with kids who had successful eye rehabilitation.