Something wakes you up in the middle of the night, or you’re searching for a light switch or door handle or phone in the dark. These sorts of things happen to us all the time. A number of minutes pass before you begin to recognize familiar things in your surroundings. This process, called ”dark adaptation,” causes us to see even when there’s very little light.
Night vision requires a combination of biochemical, physical and neural mechanisms – for granted. Let’s have a closer look at how this works. The retina is a layer of cells at the back of the eye. The section of the retina behind the pupil that is responsible for the point of focus is called the fovea. The retina is made up of rod-shaped and cone-shaped cells. The rod cells are able to function even in low light conditions. They are not found in the fovea. As you may know, the details and colors we see are detected by the cones, while rod cells allow us to see black and white, and are light sensitive.
How does this apply to being able to see in the middle of the night? When you want to see something in the dark, 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.
Another method by which your eye responds to the dark is by your pupils dilating. It requires approximately one minute for the pupil to fully enlarge but your eyes will get better at seeing in the dark over a half hour period.
Here’s an example of dark adaptation: if you go from a very bright place to a darker one for example, when coming inside after spending time in the sun. It takes a few noticeable moments until your eyes fully adjust to regular indoor light. If you go back into the brightness, that dark adaptation will be lost in a moment.
This is actually why so many people have difficulty driving their cars at night. When you look directly at the headlights of an approaching vehicle, you are briefly blinded, until that car passes and you readjust to the night light. A helpful way to avoid this is to avoid looking right at the car’s lights, and instead, try to allow your peripheral vision to guide you.
There are a number of things that could, hypothetically cause trouble with night vision. These include not getting enough Vitamin A in your diet, cataracts, glaucoma, or some other visual obstruction. If you detect that you have trouble in the dark, schedule an appointment with one of our eye doctors who will be able to identify and rectify it.