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Ask the Medical Expert Archives 2000-2004

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Worsening Night Vision
January 2000

Q. As I've gotten older, my eyesight has begun to get worse. My doctor said I could use glasses for night driving, but that I didn't have to fill the prescription if I didn't want to. How common is this and why is night driving impacted? I'm 66 and have no other ailments, thankfully.

A. It is common for eyesight to get worse as you get older. The most common problem (presbyopia) occurs in people starting around the age of 40 and makes it difficult for them to see up close, thus the need for reading glasses. A second problem that can occur later in life are cataracts. Cataracts are a process within the lens of the eye where the lens becomes cloudy, not letting as much light through. Glasses tend not to help this problem.

Night vision is often worse than daytime vision, and this is why the eye doctor checks your vision in a dark room. In the dark your pupils dilate to allow more light in. The larger pupil forces the lens of the eye to work harder in order to focus it on the retina. Thus, vision is worse at night in part because the eye has to work harder to do its job, and any impairment in your vision becomes more obvious. In addition, certain cataracts are apparent only when the eye is dilated, and this may be another source of your problem. You can learn more about cataracts at: http://www.nei.nih.gov/publications/cataracts.htm

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