Many people have more difficulty seeing clearly at night than they should. This condition is called Nyctalopia in which the retina does not regenerate a pigment called visual purple. This purplish-red pigment prevents night blindness but can become bleached out when the eyes are exposed to strong sunlight or if the retina is deficient in vitamin A.
This condition should not be confused with the normal reduction of vision we all experience at night. The reason for this is that as the light gets less, the pupil (that little hole in the center of the eye) opens wider to allow more light to enter. As photographers know, the smaller the aperture, the sharper the picture. So when the pupil gets larger, the “picture” is not quite as sharp.
Not sure? Your optometrist can measure your dark adaptation and determine if you have night blindness. He may prescribe sunglasses to block out infrared rays of the sun or may suggest an increase of vitamin A in your diet.