What is 20/20 Vision?

What is 20/20 Vision?Author: Jennifer Kimberley If you have what has been determined as humanity’s “normal” eyesight, you have 20/20 vision. In countries which use metric measurements, it is called 6/6 vision, referring to meters instead of feet. 20/20 vision is not “perfect” vision, but it is clear at all distances, needing no glasses or contact lenses. Vision can be better than 20/20, so let’s look at that further down this article. The Snellen Eye Chart Most of us are familiar with that eye chart which has a single large letter at the top (usually an “E”) and rows of progressively smaller letters below it. There are some variations on the most common version of this chart. In all versions, one line is designated as the “normal vision” line and the others test your vision relative to that “normal” line. When your eye doctor tests your vision for a glasses or contact lens prescription, the eye chart is seen through an ophthalmic device called a phoropter.

You rest your chin and forehead against smooth surfaces and look with one eye at a time at the lighted chart inside the aperture. There are also printed charts that can hang on the wall, and these can test your vision too, but the phoropter is more precise. Instead of you having to physically stand a certain distance away from it, distance is simulated by the phoropter’s optics.

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03.05.2010