Tuesday, February 24, 2009

How To Take The Internet-Based Snellen Eye Test

Ok, I found this website where you can test your eyesight ONLINE - get it? Isn't it cool? Well, this is the instruction on how you do such thing,

Use a standard ruler to measure the length of the big "E" at the top of the chart. Then multiply that number by 2.838. For example, if the big "E" is 2 inches in length, you will need to sit 5' 8" from the screen. Once you are at the proper distance, start reading the letters starting at the top. When you reach a line of letters that you cannot read, the line above it will be your approximate vision strength. Keep in mind that this is not an official medical diagnosis, you must see a qualified eye doctor for that. When you're done, scroll down for more information about the results of your Snellen Eye Test.

About The Results Of Your Snellen Eye Test

Let's suppose you can't read the letters on the 20/20 line, but you can make out the letters on the 20/40 line above it. That means that you can see at 20 feet what those with normal vision can see at 40 feet. You have 20/40 vision. If all you could see was the large E at the top of the Snellen Chart, then your vision would be 20/400. You'd be seeing at 20 feet what a person with normal vision can see at 400.

Thanks to today's corrective lens technology and surgical techniques, having less than 20/20 vision is rarely a major problem. The problems begin when the vision cannot be corrected to 20/20 with glasses, contact lenses, or corrective surgery. There are people, for example, who can barely read that 20/400 Snellen E with their naked eyes, but once they put on their glasses or contacts they can pass the eye test for a driver's license. They may be blind without glasses, but not with them. The legal definition of blindness, by the way, is vision that cannot be corrected to better than 20/200.


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