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Night Vision: How Does it Work?

Something wakes you up in the middle of the night, or perhaps you’re trying to find the light switch or door in a room with the lights off. These sorts of things happen to us all the time. At first you can’t see, but gradually the things in the room begin become visible. This is called ”dark adaptation” and it helps our eyes get used to low light settings.

In order for night vision and dark adaptation to be successful, many physiological, neurological and biochemical mechanisms have to take place behind the scenes. But how does this work? The retina is a layer of cells at the back of the eye. The area of the retina directly across from the pupil that is responsible for sharp focused vision is called the fovea. The retina is made up of cone cells and rod cells, named for their respective shapes. The rod cells have the capacity to function better than cone cells in low light conditions but they are absent from the fovea. What’s the difference between these two cell types? In short, cones help us see color and detail, and rod cells help us visualize black and white, and are light sensitive and detect movement.

How does this apply to seeing in the dark? When you want to see something in the dark, like a small star in a dark sky, instead of focusing right on it, try to use your peripheral vision. Since there no rods in the fovea, you’ll see better if you avoid using it when it’s dim.

Another way your eye responds to darkness is by your pupils dilating. Your pupil dilates to its maximum size within 60 seconds but it takes approximately 30-45 minutes for the eye to fully adapt.

Dark adaptation occurs if you go from a very light-filled place to a darker one for example, when you go inside after being out in the sun. It’ll always require a few moments for your eyes to get used to normal indoor light, but if you go back into the brightness, those changes will disappear in a flash.

This is actually why a lot people have trouble driving at night. When you look right at the headlights of a car heading toward you, you are briefly unable to see, until that car is gone and you readjust to the night light. To prevent this, don’t look right at headlights, and instead, try to allow peripheral vision to guide you.

If you’re struggling to see at night or in the dark, book a consultation with your eye care professional who will see if your prescription needs updating, and rule out other reasons for decreased vision, such as macular degeneration or cataracts.

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