That's a load of bull.
I am required to wear an eyepatch by advice of my doctor, and let me assure you, it is nothing you'd ever want to go to battle with voluntatrily. After a few days, you lose every sense of depth perception and this sense is vital for any hand- to hand or artillery action.
Give it a try yourself. Wear an eyepatch for a few days and try to perform even the simplest tasks like eating in a restaurant (i.e. at a table with whose dimensions you are not accustomed to). But you'd better not be driving with that eyepatch, or things would get real nasty.
Bowie Vision
I had to wear an eyepatch for a while. When I took it off at night sometimes I'd have double vision for a while until my eyes got use to working together again.
I have been in combat situations where I had to enter a dark building from bright sunlight.In those cases I would just tightly close my right eye for a bit so that I would have at least one pupil dilated.
-CS