Normal Refraction (shown above)
Nearsightedness ( Myopia ):
Myopia, or nearsightedness, occurs when light rays are focused in front of the retina instead of directly on the retina. To treat nearsightedness, the cornea must be made flatter. This is accomplished by removing tissue from the center of the cornea.
Regular astigmatism occurs when light rays are focused at more than one point on the retina. To treat astigmatism, the cornea must be made more spherical. By changing the pattern of the beam, tissue is removed in one direction more than the other.
Farsightedness ( Hyperopia ):
Hyperopia, or farsightedness, occurs when light rays are not bent enough to focus on the retina. To treat farsightedness, the central cornea must be made steeper. This is accomplished by directing the laser beam to remove tissue from around this area.
As we get older, we gradually lose the ability to change focus from distance to near. Usually beginning in their 40’s, people experience blurred vision at near points such as when reading, sewing or working on the computer. This condition is called presbyopia and it makes reading and other close work increasingly difficult. As this occurs, people who have been nearsighted or farsighted begin to wear bifocals. People who have never worn glasses begin to wear reading glasses for close-up work.
The excimer laser is not used to treat this condition because reshaping the cornea will not affect the aging changes occurring to the lens inside the eye. However, a laser vision correction option called monovision is available.
With this type of treatment, the surgeon fully treats one eye for distance, and the other eye for near vision. This laser vision correction treatment leaves one slightly nearsighted eye for good near vision without glasses.