Like the Air Force, you must have normal colour vision and depth perception. Before flight training begins, your vision must be 20/40 or better(correctable with glasses to 20/20) in each eye. During flight training, vision must not go worse than 20/100(correctable with glasses to 20/20) in each eye. After flight training graduation, if your vision has dropped to 20/200 or worse, you have to have a waiver for carrier operations. If it gets even worse than 20/400, pilots can only fly aircraft that have dual controls(ie, aircraft with co-pilot).