There are four types of refractive errors:
- Myopia, or Nearsightedness
- Hyperopia, or Farsightedness
In the normal eye, the cornea and the lens focus incoming rays of light forming an image that lies directly on the retina (the inside surface of the eye). When this happens the image is in perfect focus.
In myopia, or nearsightedness, the incoming rays of light are bent too much and therefore fall in front of the retina causing distant objects to appear blurry. This happens because the cornea is too steep and can be corrected by flattening the cornea using the excimer laser.
In hyperopia, or farsightedness, the incoming rays of light are not bent enough and therefore fall behind the retina causing objects to appear blurry. This happens because the cornea is too flat and can be corrected by steeping the cornea using the excimer laser. Unlike myopia, hyperopia is usually a progressive condition, especially as an individual matures. Because of this, hyperopia, over years, may experience a higher rate of retreatment.
In astigmatism, the image inside of the eye is not focused to a single point on the retina, but separate points causing the image to appear blurry. The excimer laser can be used to correct astigmatism by reshaping the cornea. Incoming rays of light then fall on one spot directly on the retina thereby creating a clear image.
In presbyopia, persons who are over forty years of age have a greater difficulty focusing at near and therefore require magnifying glasses to aid with near tasks. This is a normal part of the maturation process and will happen to you whether or not you pursue the option of refractive surgery. You and Dr. Muller should discuss the option of purposefully leaving your nondominant eye slightly undercorrected (a form of monovision) to help with near tasks. By creating a customized treatment plan for you, Dr. Muller can reduce, or eliminate, your need for reading glasses.