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Night Vision: How Does it Work?



Everyone's found themselves in the dark, at one time or another. Gradually, the things in the room begin take shape. This is called ''dark adaptation''.

In order for night vision and dark adaptation to occur, many physiological, neurological and biochemical mechanisms must take place behind the scenes. So how does it actually happen? Let's start by exploring some eye anatomy. The retina is a layer of cells at the back of the eye. The section 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 rod-shaped and cone-shaped cells. The rod cells have the capacity to function better than cone cells in low light conditions. Those cells are absent from the fovea. You may have heard that the cones help us perceive color and detail, while the rods are sensitive to light and detect movement.

Considering these facts, if attempting to make out an object in the dark, like the edge of the last stair in a dark basement, 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.

In addition to this, the pupils dilate when it's dark. It takes fewer than sixty seconds for the pupil to fully dilate but it takes approximately half an hour for the eyes to achieve full light sensitivity.

You'll experience dark adaptation when you go from a very bright area to a dim area for example, when you go inside after being out in the sun. It'll always require a few moments until you begin to adapt to regular indoor light. Then if you walk back out into the brightness, those changes will vanish in a moment.

This is actually one reason behind why a lot people don't like to drive at night. If you look directly at the ''brights'' of a car heading toward you, you are briefly unable to see, until that car passes and you once again adjust to the night light. A helpful way to prevent this sort of temporary blindness is to avoid looking directly at headlights, and learn to try to allow your peripheral vision to guide you.

If you're beginning to find it challenging to see when it's dark, book an appointment with our doctors who will see if your prescription needs updating, and rule out other and perhaps more serious causes for poor night vision, like cataracts and macular degeneration.