Mast

Vision

Peoria and Bloomington, Illinois

Understanding your vision - visual acuity and visual quality

Visual acuity is a quantitative measure of your vision, establishing where your vision is placed on a numeric scale. If your visual acuity is determined to be 20/20, then you are able to see at 20 feet what a person with normal vision sees at 20 feet. If you have 20/40 vision, then you see at 20 feet what a person with 20/20 vision would see at 40 feet. If you are fortunate enough to have 20/15 vision, then you can see at 20 feet what others would have to move closer (15 feet) to see.

Your visual acuity is an important measure of your vision. Many common problems such as nearsightedness, farsightedness and astigmatism can be identified by this measurement.

There are also qualitative factors affecting your vision, such as your ability to perceive subtle contrast changes. Contrast sensitivity is a measure of the ability to discern subtle changes in a visual image. Many routine visual tasks, such as recognizing a face, rely more upon contrast sensitivity than visual acuity. Problems believed to be associated with poor visual quality are normally most apparent in low-light situations.

Problems with visual quality can be identified with a process called wavefront mapping. Wavefront maps are plotted by passing a narrow ray of eye-safe light through the optical system and measuring the optical distortions as the light exits the eye. These patterns are then compared with the flat wavefront maps associated with normal vision.

It is possible to have very good visual acuity yet have poor visual quality, and vice versa. Therefore, understanding your vision requires taking both the quantitative and qualitative measures into consideration. It's important to consider both as you make your decision about Laser Vision Correction.

Common vision disorders

Clear vision in the normal eye is the result of light rays passing through the cornea and focusing on the retina. The following disorders are typically the result of corneal irregularities that can be improved through Laser Vision Correction.

  • Nearsightedness - occurs when the cornea is too steep or the eye is too long. This causes the light to focus in front of the retina, causing distant objects to appear blurred.
  • Farsightedness - occurs when the cornea is too flat or the eye is too short. This causes the light to focus behind the retina, causing near objects to appear blurred.
  • Astigmatism - occurs when the cornea is football-shaped, or is curved more in one direction than the other. This causes light to focus on more than one point, resulting in blurry and distorted vision with both near and distant objects.

If you live in Central Illinois and believe you might have a vision disorder, or have any other questions about your eyes and ocular health in general, please contact us today to arrange a consultation.