Something wakes you up in the middle of the night, or maybe 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 eyes to adjust to the dark. We call this ''dark adaptation'' and it lets our eyes get used to low light settings.
Many people don't know that night vision is dependent upon the cooperation of physical, neural and biochemical mechanisms. So how does it actually happen? Firstly, let's examine the eye and its anatomy. The retina is a layer of cells at the back of the eye. The portion of the retina directly behind the pupil which produces sharp focused vision is called the fovea. The retina comprises rod-shaped and cone-shaped cells. The rod cells are able to function more efficiently than cone cells in low light conditions but they are absent from the fovea. You may have heard that the details and colors we see are sensed by the cones, while rod cells are sensitive to light.
So, if you're trying to get a glimpse of something in the dark, it's much more efficient to focus on something right next to it. By looking to the side, you use the rods, which work better in the dark.
Another method by which your eye responds to darkness is by your pupils dilating. The pupil reaches its biggest capacity in about a minute but it takes about 30 minutes for your eyes to fully adapt.
Dark adaptation occurs when you walk into a darkened movie theatre from a bright area and struggle to find a seat. But after a few minutes, you get used to the situation and before you know it, you can see. This same thing occurs when you're looking at stars at night. Initially, you probably won't be able to actually see that many. As you keep gazing, your eyes will dark adapt and millions of stars will gradually appear. Despite the fact that it takes a few noticeable moments to get used to the dark, you'll always be able to re-adapt to exposure to bright light, and this resets any dark adaptation that had developed where it was darker.
This explains one reason behind why a lot people have trouble driving their cars at night. When you look right at the ''brights'' of an oncoming car, you are briefly blinded, until you pass them and your eyes once again adjust to the night light. A good way to prevent this sort of temporary blindness is to avoid looking right at the car's lights, and instead, use your peripheral vision to observe oncoming traffic at night.
If you're finding it challenging to see when it's dark, schedule a consultation with our doctors who will be able to shed some light on why this is occurring, and rule out other and perhaps more severe causes for poor night vision, like macular degeneration or cataracts.