In the Middle of the Night: Seeing in the Dark

Imagine your house loses power and suddenly, you need to locate a flashlight or the fuse box. It takes a few minutes for your eyes to adjust to the dark. This process is known as ''dark adaptation'' and it helps our eyes adjust to the dark.

In order for night vision and dark adaptation to occur, many physiological, neurological and biochemical mechanisms must take place behind the scenes. Let's talk about how your eye actually operates in these conditions. The retina is a layer of cells at the back of the eye. The section of the retina directly across from the pupil which produces the point of focus is called the fovea. The retina is made up of rod-shaped and cone-shaped cells. The rods 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? In short, details and colors we see are detected by the cones, while rod cells allow us to see black and white, and are light sensitive.

Let's put this all together. Imagine you're attempting to focus on an object in the dark, you'll be better off if you look at something next to it. If, on the other hand, you focus on the object itself, you'll use the fovea, which is made up of cone cells that are less responsive in low light conditions.

Your pupils also dilate when it's dark. Your pupil grows to it its biggest capacity in less than a minute; however, your eyes will get better at seeing in the dark over a 30 minute time frame and, as you've experienced, during this time, your ability to see in the low light setting will increase greatly.

Here's an example of dark adaptation: when you exit a bright area and enter a dim one, for example, when you go inside after being out in the sun. Even though you need several moments to adapt to the darker conditions, you will immediately be able to re-adapt upon returning to bright light, but then the dark adaptation process will have to begin from scratch if you go back into the dark.

This is actually one reason behind why a lot people don't like to drive when it's dark. If you look right at the ''brights'' of an oncoming car in traffic, you are momentarily blinded, until you pass them and your eyes readjust to the night light. A helpful way to prevent this sort of temporary blindness is to avoid looking directly at headlights, and instead, try to allow peripheral vision to guide you.

There are a number of things that could, hypothetically lead to difficulty with night vision. These include not getting enough Vitamin A in your diet, macular degeneration, cataracts, glaucoma, and others. If you notice that you have problems with dark adapting, call to make an appointment with one of our eye doctors who will be able to shed some light on the issue.