Why pirates wear one eye cap or patches?the fact

Generally you can see in all the movies in Hollywood that pirates of sea wear a one eye patches.

What is the reason?

This is because when the pirates fights with another ship people's.

They go into in down in the ship .

And there is dark .So the cap which pirates wear they removes it by their eye by this he can see in the dark.

The cap provides pirates night vision because of it he can see in dark or night.