Sometimes you get ready for bed and turn off the light, but you just can’t seem to doze off. You open your eyes and all you see is black. You notice that it is almost impossible to see anything for a couple of moments before your sight gradually improves. This process, ”dark adaptation,” causes our eyes to adjust to the dark.
In order for night vision and dark adaptation to happen, several physiological, neurological and biochemical mechanisms must take place behind the scenes. So how does this work? Your eye takes in various forms of light using rod cells and cone cells, which are found at the back of the eye; or, to be precise, on the retina. Together they form the sensory layer that gives your eye the ability to see light and color. The rod and cone cells are found throughout your entire retina, save for the small area called the fovea, where there are only cone cells. The fovea provides detailed vision, such as when reading. What’s the functional difference between these two cell types? Basically, cones contribute to color vision, while rod cells are sensitive to light.
Considering these facts, if you’re trying to find something in the dark, like a distant star in a dark sky, instead of focusing right on it, try to use your peripheral vision. It works by utilizing the light-sensitive rod cells.
Furthermore, the pupils, the black circles in the middle of your eyes, dilate in response to darkness. It takes less than a minute for your pupil to completely dilate but it takes about half an hour for you to achieve full light sensitivity.
Dark adaptation occurs when you enter a darkened theatre from a well-lit lobby and have trouble finding a seat. But soon enough, you adapt to the dark and before you know it, you can see. This same thing occurs when you’re looking at the stars in the sky. At the beginning, you won’t see many. Keep looking; as your eyes continue to dark adapt, millions of stars will gradually appear. It’ll always require a few moments until your eyes fully adapt to regular indoor light. If you go back into the brightness, those changes will disappear in a moment.
This is actually why many people prefer not to drive when it’s dark. If you look right at the headlights of a car heading toward you, you may find yourself momentarily unable to see, until you pass them and you readjust to the night light. To prevent this, don’t look right at headlights, and instead, try to allow peripheral vision to guide you.
If you’re having trouble seeing at night or in the dark, call us to schedule an appointment with your eye care professional who will confirm that your prescription is up to date, and rule out other reasons for decreased vision, such as macular degeneration or cataracts.