Sometimes you go to bed and turn off the light, but you just can’t seem to doze off. You open your eyes and it’s all dark. Gradually, the things in the room begin take shape. This process is known as ”dark adaptation”.
In order for night vision and dark adaptation to work, many physiological, neurological and biochemical mechanisms have to take place behind the scenes. 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 portion of the retina directly across from the pupil that is responsible for sharp focused vision is called the fovea. The retina comprises rod-shaped and cone-shaped cells. The rods have the capacity to function even in low light conditions. Those cells are not found in the fovea. As you may know, the cones contribute to color vision, while the rods let us see black and white, and are light sensitive.
Now that you know some background, let’s relate it to dark adaptation. If trying to find something in the dark, like a distant star in the night sky, you’ll be better off if you look at something off to the side of 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.
Your pupils also dilate in the dark. Your pupil reaches its biggest capacity in less than a minute but your eyes will get better at seeing in the dark over a half hour time frame. During this time, your eyes become 10,000 times more sensitive to light.
Here’s an example of dark adaptation: when you go from a very bright place to a dim one for example, when you go inside after sitting in the sun. While your eyes require a few noticeable moments to adapt to the dark, you’ll always be able to re-adapt upon your return to bright light, but if you return to the darker setting, your eyes will need time to adjust again.
This is actually one reason behind why many people prefer not to drive when it’s dark. When you look right at the ”brights” of a car heading toward you, you are briefly unable to see, until that car is gone and you once again adjust to the night light. A helpful way to avoid this is to avoid looking directly at the car’s lights, and learn to try to allow peripheral vision to guide you.
There are several conditions that could be the cause of difficulty seeing in the dark, including: not getting enough Vitamin A in your diet, macular degeneration, cataracts, glaucoma, and others. Should you begin to detect that you experience problems with seeing at night, book an appointment with one of our eye doctors who will be able to get to the source of the problem.