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Night Vision: How Does it Work?

Let's say there's a power outage and you need to hunt around for a flashlight or the fuse box. 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 closer look at how all this operates. The retina is a layer of cells at the back of the eye. The section of the retina directly across from the pupil which produces sharp focused vision is called the fovea. The retina is made up of cone cells and rod cells, named for their respective shapes. The rods have the capacity to function better than cone cells in low light conditions. Those cells are not found in the fovea. You might already be aware that the cones help us see color and detail, while rod cells allow us to see black and white, and are light sensitive.

So, if looking at an object in the dark, instead of looking directly at 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.

Another method by which your eye responds to darkness is by your pupils dilating. The pupil grows to it its maximum size within 60 seconds but it takes approximately 30-45 minutes for you to achieve full light sensitivity.

You'll experience dark adaptation when you go from a very light-filled place to a darker area for instance, when coming inside after spending time in the sun. It'll always take a few moments until you begin to get used to regular indoor light, but if you go back outside, those changes will disappear in a flash.

This is why so many people prefer not to drive when it's dark. When you look at the headlights of an approaching car, you may find yourself momentarily unable to see, until that car passes and you once again adjust to the night light. A good way to prevent this sort of temporary blindness is to avoid looking directly at the car's lights, and learn to use your peripheral vision to observe oncoming traffic at night.

If you find it increasingly difficult to see when it's dark, call us to schedule a consultation with your eye doctor who will check that your prescription is up to date, and rule out other and perhaps more serious reasons for poor night vision, like cataracts and macular degeneration.