Why do pilots use red glasses?

For maximum utilization of scotopic vision( a vision of eye in low light), 20 to 30 minutes in total darkness are required to attain satisfactory retinal dark adaptation. An alternative is to have the aircrew member wear red goggles for 20 to 30 minutes before flying. When worn in normal illumination, red goggles will not interfere significantly with the ability to read most maps, charts, manuals, etc., as long as the printing is not in red ink. Red goggles block all light except red, which enhances rod dark adaptation because red light does not stimulate the scotopic system.