Complex sentence: A rock smashed into his eye and he had to go to the eye doctor for many years to receive treatment, and after some time the eye healed and exceeded the normal 20/20 eye vision, reaching 20/10.
Split into simpler sentences: A rock smashed into his eye and he had to go to an optometrist for several years for treatment. After the eye healed, it was determined that Jack's vision had exceeded the normal 20/20 eye vision, reaching 20/10.