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A Closer Look at Night Vision



You wake from a dream in the middle of the night, or you're looking for the light switch or door in a dark room. These sorts of things happen to us all the time. It takes a couple of minutes for your vision to return. This process, ''dark adaptation,'' allows our vision to adjust to the dark.

Night vision requires a number of biochemical, physical and neural mechanisms - for granted. So how does this work? Every eye takes in various forms of light using rod cells and cone cells, which are found on the retina at the back of the eye. Together they make up the sensory layer that enables the eye to pick up light and color. The rod and cone cells exist throughout the entire retina, save for the small area known as the fovea, where there are only cone cells. That part is necessary for detailed sight, for example when reading. What's the difference between rods and cones? Basically, details and colors we see are detected by the cones, and the rods are sensitive to light.

Let's put this all together. Imagine you want to see something in the dark, instead of looking right at it, try to look just beside it. You want to maximize the use of the rod cells in low light, and avoid relying on your cone-rich fovea, even though it seems counter-intuitive to look away from the object you want to see.

Another method by which your eye responds to the dark is by your pupils dilating. Your pupil reaches its biggest capacity within a minute but it takes about 30-45 minutes for your eyes to achieve full light sensitivity.

Here's an example of dark adaptation: when you go from a very light-filled area to a darker area for instance, when you go inside after being out in the sun. It'll always require a few moments for your eyes to get used to normal indoor light, but if you go back outside, that dark adaptation will be lost in the blink of an eye.

This explains why a lot people prefer not to drive when it's dark. When you look right at the lights of an approaching vehicle, you are briefly blinded, until you pass them and you once again adjust to the night light. A good way to prevent this sort of temporary blindness is to avoid looking right at the car's lights, and instead, use your peripheral vision to observe oncoming traffic at night.

If you're struggling to see when it's dark, book a consultation with our doctors who will confirm that your prescription is up to date, and eliminate other reasons for decreased vision, such as macular degeneration or cataracts.