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Night Vision: How Does it Work?

Everyone's found themselves in the dark, at some point in their lives. You need several moments to get used to the dark and then you are able to see better. This process, ''dark adaptation,'' causes people to adjust to the dark.

Night vision requires a whole assortment of biochemical, physical and neural mechanisms - for granted. Let's have a closer look at how this works. Every eye takes in various forms of light using rod cells and cone cells, at the back of the eye; or, to be precise, on the retina. Together they form the sensory layer. This is the part that enables the eye to detect light and color. These cells are distributed evenly throughout the entire retina, except for in the small area opposite the pupil known as the fovea, where there are only cone cells. That part is primarily responsible for detailed sight, for example when reading. What's the difference between these two cell types? Basically, details and colors we see are sensed by cone cells, while the rods allow us to see black and white, and are light sensitive.

Considering these facts, if you want to see something in the dark, like the edge of the last stair in a dark basement, it's much better to look at the area off to the side of it. It works by using the light-sensitive rod cells.

Another part of the process is pupil dilation. It takes fewer than sixty seconds for the pupil to completely enlarge; however, dark adaptation will continue to increase for the next half hour and, as you've experienced, during this time, your ability to see in the low light setting will increase remarkably.

Here's an example of dark adaptation: when you go from a very light-filled place to a dim one for example, when you go inside after spending time in the sun. Despite the fact that you need several moments to get used to the dark, you will immediately be able to re-adapt to exposure to bright light, but then the dark adaptation process will have to begin from scratch if you go back into the dark.

This is actually why so many people have trouble driving at night. If you look at the ''brights'' of an oncoming car in traffic, you are briefly blinded, until that car passes and your eyes readjust to the night light. A helpful way to prevent this sort of temporary blindness is to avoid looking directly at headlights, and learn to use your peripheral vision to observe oncoming traffic at night.

There are several things that may cause inability to see at night, including: a nutritional deficiency, cataracts, glaucoma, or some other visual obstruction. Should you begin to detect that you have difficulty seeing in the dark, schedule an appointment with one of our eye doctors who will be able to shed some light on the issue.