HomeVision DysfunctionsAbout 20/20

About 20/20

When most of us think of “perfect” vision, we think of 20/20.

We assume that if we have 20/20, our visual system function is normal. If we don’t have 20/20, we need a lens correction to restore our vision to 20/20 – then, our visual system function has been restored to normal. In fact, nothing could be further from the truth!

And what is this 20/20 stuff anyway? Over 100 years ago, a Dr. Snellen determined (by the best scientific methods of the day) the smallest target size a human eye could see. This target size came to be labeled (in the United States) a size 20 letter at a distance 20 from the eye. Thus, 20/20 means you can see a size 20 letter at 20 feet away. So, 20/40 means you can see a given letter size at 20 feet at what a person with 20/20 can see at 40 feet. Sound confusing? It is!!!!!!

Thus, 20/20 is merely a measure of visual acuity (clarity) at a 20 foot distance.

School vision screenings are usually limited to measuring distance visual acuity. Most Primary Care Vision Evaluations access the possible need for lenses to correct to 20/20 and eye health. Most Primary Care Vision Evaluations do not measure Binocular Vision Function (the ability of the two eyes to team and coordinate together), or the ability to understand or get meaning from the 20/20 visual input.

If prescription lenses are required, the lenses will often provide optical correction for:

• Astigmatism – much of the time, light entering the eye horizontally is refracted differently than light entering the eye vertically. Depending upon the amount of Astigmatism, far and near point vision will be blurred. Often, a lens prescription for Astigmatism will also include a correction for Hyperopia or Myopia
• Myopia (nearsightedness) – the length of the eye is too long, or the optics too strong. Depending upon the amount of Myopia, far point vision is blurred – however, near point vision may be clear or blurred.
• Hyperopia (farsightedness) – the length of the eye is too short, or the optics too weak. Depending upon the amount of Hyperopia, both far and near point objects are perceived as blurred.

At Hope Clinic a FULL Functional or Neuro-Optometric Evaluation measures Binocular (both eyes) function, in addition to the standard eye refraction to 20/20 and eye health. Visual Motor Guidance, Ocular Motility (eye tracking), Accommodation (eye focusing), Vergence (eye alignment) and Visual Information Processing/Visual Perception abilities are documented. From these medical findings, treatment options are discussed with each patient and/or family members.

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