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In the Middle of the Night: Seeing in the Dark

Something wakes you up in the middle of the night, or perhaps you're searching for a light switch or door handle or phone in a dark room. These sorts of things happen to us all the time. Your eyes normally require a few minutes to adjust to the dark and then the your surroundings come back into view. This remarkable process is ''dark adaptation''.

Night vision involves a whole assortment of biochemical, physical and neural mechanisms - for granted. But how does this work? The retina is a layer of cells at the back of the eye. The section of the retina 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. They are absent from the fovea. What's the difference between rods and cones? Basically, details and colors we see are detected by the cones, and the rods are sensitive to light and detect movement.

So, if you want to see something in the dark, it's much better to try to look at it with your peripheral vision. 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 dilates to its largest diameter in less than a minute; however, your eyes will keep adapting over a half hour time frame.

Dark adaptation occurs when you leave a bright area and enter a dim one, for example, walking inside after spending time in the sun. Even though your eyes require a few noticeable moments to begin to see in the dark, you'll always be able to re-adapt upon your return to bright light, and this resets any dark adaptation that had developed where it was darker.

This is actually why many people don't like to drive when it's dark. When you look at the lights of a car heading toward you, you are momentarily unable to see, until that car passes and your eyes once again adjust to the night light. A good way to avoid this is to avoid looking right at headlights, and learn to try to allow your peripheral vision to guide you.

If you're having trouble seeing at night or in the dark, call us to schedule an appointment with our doctors who will be able to shed some light on why this is happening, and eliminate other reasons for worsened vision, such as macular degeneration or cataracts.