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Home » What's New » Turn Out the Lights: How Does Night Vision Work?

Turn Out the Lights: How Does Night Vision Work?

Picture this: your house loses power and you need to hunt around for a flashlight or the fuse box. A number of minutes pass before you can see again. This is called ”dark adaptation”.

Many people don’t know that night vision is dependent upon the cooperation of physical, neural and biochemical mechanisms. So how does this work? The retina is a layer of cells at the back of the eye. The portion of the retina directly opposite the pupil that is responsible for the point of focus is called the fovea. The retina is made up of rod-shaped and cone-shaped cells. The rod cells are able to function more efficiently than cone cells in low light conditions but those cells are absent from the fovea. You may have learned that the details and colors we see are sensed by the cones, and rod cells are sensitive to light.

This information is significant because, when you want to see something in the dark, like the dresser in a darkened room, you’ll be better off if you view it with your peripheral vision. By looking to the side, you use the rods, which work better in the dark.

Another method by which your eye responds to darkness is by your pupils dilating. Your pupil dilates to its biggest capacity in about a minute; however, your eyes will keep adapting over a 30 minute period. During this time, your eyes become 10,000 times more sensitive to light.

Here’s an example of dark adaptation: when you leave a bright area and enter a dim one, for example, when you go inside after being out in the sun. While your eyes require a few noticeable moments to begin to see in the darker conditions, you will immediately be able to re-adapt to exposure to bright light, but then the dark adaptation process will have to begin from scratch if you go back into the dark.

This explains one reason behind why a lot people have trouble driving their cars at night. If you look right at the headlights of a car heading toward you, you are momentarily blinded, until you pass them and your eyes once again adjust to the night light. To prevent this, try not to look right at the car’s lights, and learn to try to allow your peripheral vision to guide you.

There are several things that could, hypothetically lead to trouble seeing at night, including: not getting enough Vitamin A in your diet, macular degeneration, cataracts, glaucoma, and others. If you detect issues with night vision, call to make an appointment with one of our eye doctors who will be able to identify and rectify it.

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