Everyone has found themselves in a dark room, at some point in their lives. After a while you begin to recognize familiar things in your surroundings. This is called ”dark adaptation” and it’s what helps our eyes see in low light settings.
In order for night vision and dark adaptation to be successful, many physiological, neurological and biochemical mechanisms have to take place behind the scenes. Let’s have a look at how all this operates. The retina is a layer of cells at the back of the eye. The area of the retina behind the pupil which produces the point of focus is called the fovea. The retina comprises rod-shaped and cone-shaped cells. The rod cells are able to function even in low light conditions but those cells are not found in the fovea. What’s the difference between rods and cones? Basically, cones contribute to color vision, while the rods help us visualize black and white, and are light sensitive.
This information is significant because, when you want to see something in the dark, like the edge of the last stair in a dark basement, you’ll be better off if you focus on something right next to it. When you do that, you use the part of the eye that has rods, which, as mentioned above, are more responsive to light, even if there isn’t much of it.
Another part of the process is pupil dilation. It requires fewer than sixty seconds for the pupil to fully dilate; however, your eyes will keep getting used to the dark over a 30 minute time frame.
Dark adaptation occurs when you leave a bright area and enter a dim one, for instance, walking inside after spending time in the sun. It’ll always require a few moments for your eyes to adjust to normal indoor light, but if you walk back out into the brightness, that dark adaptation will vanish in a moment.
This is one reason behind why many people don’t like to drive when it’s dark. When you look directly at the headlights of a car heading toward you, you may find yourself briefly unable to see, until that car passes and your eyes once again adjust to the night light. To prevent this, don’t look right 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, including: diet-related vitamin deficiencies, cataracts, glaucoma, or some other visual impediment. If you notice that you have problems with night vision, book an appointment with one of our eye care professionals who will be able to shed some light on the issue.