Holladay LASIK Institute - Patient Education

What is Normal Vision?

Vision or visual acuity is tested by reading a Snellen eye chart at a distance of 20 feet. By looking at lots of people, eye doctors have decided what a "normal" human being should be able to see when standing 20 feet away from an eye chart. If you have 20/20 vision, it means that when you stand 20 feet away from the chart you can see what a "normal" human being can see. (In metric, the standard is 6 meters and it's called 6/6 vision). In other words, if you have 20/20 vision your vision is "normal" -- a majority of people in the population can see what you can see at 20 feet.

If you have 20/40 vision, it means that when you stand 20 feet away from the chart you can only see what a normal human can see when standing 40 feet from the chart. That is, if there is a "normal" person standing 40 feet away from the chart, and you are standing only 20 feet away from the chart, you and the normal person can see the same detail. 20/100 means that when you stand 20 feet from the chart you can only see what a normal person standing 100 feet away can see. 20/200 is the cutoff for legal blindness in the United States.

You can also have vision that is better than the norm. A person with 20/10 vision can see at 20 feet what a normal person can see when standing 10 feet away from the chart.

Common Refractive Disorders:

The most common refractive vision disorders are nearsightedness (myopia), farsightedness (hyperopia), and astigmatism. While most times these disorders occur separately in a person's vision, they can be produced by the cornea.

Nearsightedness (myopia) occurs when the cornea of the eye is too steep in curvature, causing light rays to focus in front of the retina instead of directly on the retina. This results in near images being in focus, while far away images are blurred.
Farsightedness (hyperopia) occurs when the cornea of the eye is too flat in curvature, causing light rays to focus behind the retina instead of directly on the retina. This results in far away images being in focus, while near images are blurred.
Astigmatism occurs when the surface of the cornea has an irregular shape to it, causing light images to focus on multiple areas within the eye. This can result in blurred or double images. As illustrated on the right, this condition can also occur in conjunction with nearsightedness.

To receive more information on the Holladay LASIK Institute's vision care services, please Contact Us or give us a call right now! The Holladay LASIK Institute offers many free brochures on the various services available to you in our office. Please see the Map and Directions to our office located at 6802 Mapleridge, Suite 200, Bellaire, Texas 77401.

Zero Percent Financing for up to 24 months is available to qualified candidates. If you have a question about your vision, do not hesitate to e-mail us at docholladay@docholladay.com or give us a call right now at the number below.