Something wakes you up in the middle of the night, or you're searching for a light switch or door handle or phone in a room with the lights off. It's happened to all of us. It takes a couple of minutes for your vision to return. This remarkable process is ''dark adaptation'' and it's what helps our eyes see in the dark.
In order for night vision and dark adaptation to be successful, several physiological, neurological and biochemical mechanisms must take place behind the scenes. Let's talk about how this works. The retina is a layer of cells at the back of the eye. The portion of the retina directly behind the pupil that is responsible for the point of focus is called the fovea. The retina is made up of cone cells and rod cells, named for their respective shapes. The rods have the capacity to function even in low light conditions but those cells are not found in the fovea. What's the difference between these two cell types? Basically, cones enable us to see color and detail, while the rods help us visualize black and white, and are light sensitive and detect movement.
This information is significant because, when you want to see something in the dark, like a dim star in a dark sky, you'll be better off if you try to look at it through your peripheral vision. 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 way your eye responds to darkness is by your pupils dilating. Your pupil dilates to its maximum size within 60 seconds; however, dark adaptation continues to develop for the next half hour 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 go from a very bright area to a dim one for example, walking inside after spending time in the sun. It takes a few noticeable moments until you begin to get used to normal indoor light, but if you go back into the brightness, those changes will be lost in the blink of an eye.
This explains why a lot people don't like to drive when it's dark. If you look at the headlights of an approaching car, you are briefly unable to see, until that car passes and your eyes readjust to the night light. To prevent this, try not to look right at headlights, and instead, try to allow peripheral vision to guide you.
If you're beginning to find it challenging to see at night or in the dark, call us to schedule an appointment with our doctors who will confirm that your prescription is up to date, and eliminate other reasons for worsened vision, such as macular degeneration or cataracts.