Answers by Mitchell Gossman, MD, an ophthalmologist at Eye Associates of Central Minnesota, located in St. Cloud
What is the most common cause of blindness?
First, what is “blindness?” This depends on the severity of vision loss. Total blindness would be defined as inability to detect any light at all. An obvious example of this would be a person who had to have both eyes surgically removed because of chronic pain, injury or tumors. Such a person would obviously have a lot of trouble doing activities such as walking down the hall or on a city street, preparing food, etc. They need help getting around unfamiliar surroundings though the help of a seeing person or a guide dog. They may also be able to get around using a white cane, to literally feel their way. It’s also possible to be completely blind in cases of severe strokes affecting both sides of the brain that process vision. The eyes may be completely healthy, and would see fine, except the brain does not perceive the images.
Then there is the matter of “legal blindness.”A “legally blind” person does have sight; in other words is not completely blind, but has significantly decreased vision. The most common cause of this in the United States is, by far, Macular Degeneration. This is a disease that affects the central part of the retina, causing loss of the finely detailed vision that allows a person to read and legally drive a car. This is defined as not being able to see any letters smaller than the 20/200 line on the eye chart, the “Big E,” in both eyes. This is strictly a legal definition for purposes of driving privileges, taxpayer deductions, disability determination, and so on. It is by no means “blindness,” and people with loss of central vision only can carry out most ordinary activities of daily living other than reading.
The next most common cause of legal blindness is in fact cataracts, even in the USA. But because cataracts are correctable with surgery, this is not as important as other causes.
The next most common cause of legal blindness is glaucoma. This causes loss of peripheral vision, and if it progresses to the point where the remaining peripheral vision is limited to 20 degrees wide in both eyes it is also defined as “legal blindness.” You may not feel the peripheral vision is as important as the central reading. However, the loss of peripheral to this extreme from any cause, including glaucoma, is very debilitating, even with ordinary activities.
Therefore, it’s so important to detect glaucoma during a routine eye exam, and to treat it properly, including taking medications.
Find out more
Mitchell Gossman, MD., and Andrea Joplin, MD., are ophthalmologists at Eye Associates of Central Minnesota in St. Cloud, and see patients from all over Central Minnesota and the St. Cloud area. They accept new patients, and appointments may be made at 320-774-3789.
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