Meet Dr. Davidson	Meet Dr. Taravella	Refractive Surgery Home	Department of Ophthalmology Home

Click on the picture to see full size. Nearsightedness or MYOPIA If the eye is too long or the optical system too powerful, light rays are focused in front of the retina.   Farsightedness, or HYPEROPIA results when the length of the eye is too short. Refractive Error: If the optical system of the eye results in poorly focused light rays, a refractive error exists in the eye. If the eye is too long or the optical system too powerful, light rays are focused in front of the retina. This is known as MYOPIA or nearsightedness, since objects that are closer to the eye can be seen better.  Farsightedness, or HYPEROPIA results when the length of the eye is too short. Objects farther away can be seen better than those close to the eye.  _______________________________ ASTIGMATISM is the result of a football shaped corneal surface (toric surface), and can cause poor vision at both near and far. All of the above refractive errors are amenable to surgical correction. _______________________________ PRESBYOPIA refers to the inability to see things up close or read without bifocals. This is due to a loss of the internal focusing mechanism inside the eye and begins at the age of 40. Many nearsighted people can read just fine without their glasses, but require a bifocal to see well with glasses on. In the same way, if nearsightedness is completely corrected, glasses may be needed to see up close. Presbyopia currently cannot be corrected with laser techniques. _______________________________ However, MONOVISION may be an option. This is a technique in which one eye (the dominant eye, usually the right) is corrected completely for distance and one eye for near vision. Although most patients can adapt to monovision, many cannot. The best indicator of the ability to adapt to monovision correction is using this type of correction in contact lenses. _______________________________ Refractive errors are measured in DIOPTERS, which is simply the inverse of the focal length of the lens needed to correct the problem. The higher the number, the stronger the lens. 1-6 diopters would be considered low myopia, 6-9 moderate, 10 and above would be high myopia. For example, a person with a minus 10 glasses prescription would have 10 diopters of power in their lens. This would have a focal length of 1/10 meter or 10 cm. Anything outside this distance would be out of focus.