What do vision numbers mean

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Visual Acuity: What is 20/20 Vision?

what do vision numbers mean

If you have an eye exam and are told you have 20/20 vision, does this mean you Visual acuity is measured by your ability to identify letters or numbers on a.


And what is "perfect vision" anyway? Visual acuity. This, literally, is the sharpness of your vision. Visual acuity is a static measurement, meaning you are sitting still during the testing and the letters or numbers you are viewing also are stationary. Visual acuity also is tested under high contrast conditions typically, the letters or numbers on the eye chart are black, and the background of the chart is white.

But what does that really mean? Kevin McKinney, MD.
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Most surveys and studies indicate that the majority of people in the United States with vision loss are adults who are not totally blind; instead, they have what is referred to as low vision. You may have heard the terms "partial sight" or "partial blindness" or even "poor vision" also used to describe low vision. Those descriptions are no longer in general use, however. Here is one definition of low vision, related to visual acuity :. Visual acuity is a number that indicates the sharpness or clarity of vision. In the United States, the Snellen Eye Chart pictured at left is a test that ophthalmologists and optometrists use to measure a person's distance visual acuity.

So, you've just had an eye exam and your eye doctor has given you an eyeglass prescription. He or she probably mentioned that you are nearsighted or farsighted , or perhaps you have astigmatism. If that's not the case, and you need an eye exam, click here to find an eye doctor near you. But what do all those numbers on your eyeglass prescription mean? This article will help you read and understand your eyeglass prescription so you can discuss it with an optician when you buy new eyeglasses. The first step to understanding your eyeglass prescription is knowing what "OD" and OS" mean. They are abbreviations for oculus dexter and oculus sinister , which are Latin terms for "right eye" and "left eye.

How to read your eyeglasses prescription

What Does 20/20 Vision Mean?

If you suffer from certain eye problems, your doctor may prescribe eyeglasses to help with your eyesight. However, your prescription for eyeglasses contains numbers and abbreviated words that you may not be able to understand. Therefore, the first step towards reading your eyeglass prescription is to understand the meaning of these abbreviations. Traditionally, the abbreviations used have been derived from Latin terms to describe information pertaining to your right and left eye. Below is a list of the most common abbreviations found on eyeglass prescriptions to help explain what they mean. They are Latin words that mean right eye and left eye respectively. OU refers to Oculus Uterque.

Visual acuity VA commonly refers to the clarity of vision. Visual acuity is dependent on optical and neural factors, i. A common cause of low visual acuity is refractive error ametropia , or errors in how the light is refracted in the eyeball. Causes of refractive errors include aberrations in the shape of the eyeball or the cornea , and reduced flexibility of the lens. Too high or too low refractive error in relation to the length of the eyeball is the cause of nearsightedness myopia or farsightedness hyperopia normal refractive status is referred to as emmetropia.

Visual acuity is usually measured with a Snellen chart. Snellen charts display letters of progressively smaller size. Fighter pilot minimum. Required to read the stock quotes in the newspaper, or numbers in the telephone book. The refractive error of the eye can be expressed in numeric terms. The power of the lenses necessary to correct your vision is measured in units called diopters see below.

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