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Night Vision: How Does it Work?

Sometimes you get ready for bed and turn off the light, but you just can’t seem to doze off. You open your eyes and all you see is black. It takes a few minutes for your eyes to adjust to the dark. This process, ”dark adaptation,” allows people to adjust to the dark.

A person with a healthy set of eyes probably takes night vision – and the biochemical, physical and neural mechanisms – for granted. Let’s have a look at how your eye actually operates in these conditions. Every eye has, in addition to other cells, rod cells and cone cells, on the retina at the back of the eye. Together they make up the sensory layer. This is the part that helps the eye pick up colors and light. Cones and rods are distributed evenly throughout your retina, save for the small area called the fovea. The fovea is made up of only cone cells, and its main function involves focusing. What’s the functional difference between rods and cones? In short, details and colors we see are sensed by the cones, while rod cells let us see black and white, and are light sensitive.

Let’s put this all together. Imagine struggling to view something in the dark, like the dresser in a darkened room, instead of focusing right on it, try to use your peripheral vision. When you do that, you use the part of the eye that has rods, which, as mentioned above, are more responsive to light, even if there isn’t much of it.

Also, the pupils dilate in low light. Your pupil reaches its biggest capacity in about a minute; however, dark adaptation continues to improve your eyesight for the next half hour.

Dark adaptation occurs when you enter a dark cinema from a bright area and have trouble finding a seat. But soon enough, you get used to the dark and before you know it, you can see. This same thing occurs when you’re looking at stars at night. At first you probably won’t be able to actually see that many. Keep looking; as your eyes continue to dark adapt, millions of stars will gradually appear. Despite the fact that your eyes require a few noticeable moments to get used to the darker conditions, you’ll quickly be able to re-adapt upon your return to bright light, but then the dark adaptation process will have to begin from scratch if you go back into the dark.

This explains why a lot people prefer not to drive when it’s dark. If you look at the ”brights” of a car heading toward you, you may find yourself briefly blinded, until that car is gone and you once again adjust to the night light. A good way to avoid this is to avoid looking right at headlights, and instead, try to allow your peripheral vision to guide you.

If you’re beginning to find it increasingly difficult to see at night or in the dark, book a consultation with our doctors who will confirm that your prescription is up to date, and eliminate other reasons for worsened vision, such as macular degeneration or cataracts.