Everyone’s found themselves in the dark, at one time or another. At first you can’t see, but gradually the things in the room begin become visible. This impressive process is ”dark adaptation”.
Night vision involves a number of biochemical, physical and neural mechanisms – for granted. But how does this work? The retina is a layer of cells at the back of the eye. The area of the retina directly behind 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 are able to function better than cone cells in low light conditions but they are not found in the fovea. What’s the difference between rods and cones? In short, details and colors we see are detected by cone cells, and the rods are sensitive to light.
This information is significant because, when looking at an object in the dark, like the dresser in a darkened room, instead of looking directly at it, try to use your peripheral vision. Since there no rods in the fovea, you’ll see better if you avoid using it when it’s dim.
Another process your eye undergoes is pupil dilation. It takes less than a minute for your pupil to fully enlarge; however, it takes about 30 minutes for the eye to achieve full light sensitivity and, as you’ve experienced, during this time, your ability to see in the dark will increase greatly.
Here’s an example of dark adaptation: when you leave a bright area and enter a dim one, for instance, when you go inside after spending time in the sun. It’ll always take a few moments until you begin to adjust to regular indoor light. Then if you walk back out outside, those changes will be lost in a flash.
This is why many people have trouble driving their cars at night. When you look right at the headlights of opposing traffic, you are momentarily unable to see, until that car passes and your eyes readjust 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 instead, try to allow your peripheral vision to guide you.
There are several things that could, hypothetically lead to difficulty with night vision. These include diet-related vitamin deficiencies, cataracts, glaucoma, or some other visual obstruction. Should you begin to suspect that you experience trouble in the dark, call to make an appointment with one of our eye care professionals who will be able to identify and rectify it.