Night Blindness

Understanding Night Blindness


Carrots can help you see the stars!


Light enters your eye and lands on light sensitive cells on the retina (back of the eye). These light receiving cells send signals to your brain where it is decoded and you see images. Visual purple is a most important light receiver, and it is composed of two parts: a protein molecule and a molecule made from vitamin A. People who have a deficiency of vitamin A cannot make enough visual purple to see well at night. This condition is called night blindness.

Night Blindness and How the Eye Works


While carrots and other vegetables, including pumpkin do not contain vitamin A, they have carotene which your liver changes into vitamin A.


One way your eyes adjust to the dark is that the pupils dilate (get bigger) so that more light can enter. When you go outdoors at night, it takes about 30 to 60 minutes for your eyes to adjust so that you can see your best in the dark. This is called night vision. Discover how light affects the size of your pupils. Sit in a brightly lit room with one eye closed. After 2 or more minutes, use a mirror to observe the size of the pupil of your open eye. Then, observe the pupil of the eye that had been closed.



One flash of white light, such as from a flashlight can cause you to lose your night vision and it takes 30 to 60 minutes to regain it. Red light affects night vision less than does white light. See page 42 of Janice VanCleave’s Constellations for Every Kid: Easy Activities that Make Learning Science Fun (Science for Every Kid Series) (Wiley, 1997) for instructions to make an astronomer’s flashlight.

You can find more fun science experiments in Janice VanCleave’s Food and Nutrition for Every Kid: Easy Activities That Make Learning Science Fun (Science for Every Kid Series) (Wiley, 1999).

What do you think?



  1. 1

    It was during the Second World War that British scientist used this piece of knowledge to their advantage. I’ve heard this story told two ways, and haven’t been able to confirm exactly what is the correct story.

    Apparently they had been running tests on night flying and the panel instrumentation of the aircraft. I believe the correct version of the story is that they discovered that green lighting enabled the pilots to better see and to have less eye strain when looking from panel to the darkened sky. This was instead of the normal red lighting on the instrument panels.

    So they changed all their planes over to the other lighting and there was a noticeable improvement in their night missions success and on flights coming back to the base.

    However, they didn’t want the information to get back to the Germans so they had the mess halls serve lots of carrots to the pilots. And would tell them, carrots help you see better in the dark!

    Like I said, this is a story I’ve heard often and can’t testify to its truth but its fun!