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Night Vision

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 you can't see anything. Your eyes normally require a few minutes to adjust to the dark and then you can see again. This remarkable process is ''dark adaptation'' and it's what lets our eyes see in low light settings.

In order for night vision and dark adaptation to work, many physiological, neurological and biochemical mechanisms have to take place behind the scenes. So how does this work? Your eye has, in addition to other cells, two kinds of cells: cones and rods, which are found at the back of the eye; or, to be precise, on the retina. Together they form the sensory layer that helps the eye detect colors and light. These cells are distributed evenly throughout your entire retina, save for the small area opposite the pupil known as the fovea. The fovea has only cone cells, and its primary function involves creating a focused image. You might already be aware that the details and colors we see are detected by the cones, and rod cells are sensitive to light and detect movement.

Considering these facts, if you want to see something in the dark, like the dresser in your darkened room, instead of looking right at it, try to look just beside it. That way, you're avoiding the use of the fovea, which only has cells that are less sensitive to low light.

The pupils also dilate in low light. Your pupil dilates to its maximum size within 60 seconds but dark adaptation continues to improve your eyesight for the next half hour and, as you've experienced, during this time, your ability to see will increase greatly.

Here's an example of dark adaptation: when you go from a very bright area to a dim one for instance, when coming inside after spending time in the sun. Despite the fact that your eyes require several moments to begin to see in the dark, you'll always be able to re-adapt upon returning to bright light, and this resets any dark adaptation that had developed where it was darker.

This explains why a lot people have trouble driving at night. When you look right at the headlights of an approaching vehicle, you are briefly blinded, until that car is gone and your eyes readjust to the night light. A helpful way to avoid this is to avoid looking directly at headlights, and learn to use peripheral vision in those situations.

There are a number of things that could potentially lead to trouble with night vision. These include not getting enough Vitamin A in your diet, cataracts, glaucoma, or some other visual impediment. If you notice that you have difficulty seeing in the dark, schedule an appointment with one of our eye doctors who will be able to identify and rectify it.