Laser Vision Correction
Lasik Overview
What is a Refractive Error?
What is Astigmatism?
What is Myopia?
What is Hyperopia?
Monovision
What is a Refractive Error?
A refractive error is a defect in the way light passes through the eye. In normal vision, light enters the eye through the cornea and is focused at a single point on the retina at the back of the eye. With a refractive error, light rays do not refract (bend) properly to achieve a single focus point. Instead, light rays focus in front of the retina, behind the retina, or at two different points. Refractive errors usually result from a defect in the length of the eye or shape of the cornea.
What is Astigmatism?
Astigmatism, a condition in which objects at all distances appear somewhat indistinct and distorted rather than sharp and clear, is caused by a misshaped cornea. Because the curve of the cornea is uneven or warped instead of an even curve, the light rays are not refracted equally in all directions. As a result, a single focus point on the retina is not achieved and distorted vision occurs.
What is Myopia?
Myopia, or nearsightedness, is a condition in which close objects are seen clearly but distant objects appear blurred. Nearsightedness results from a lengthened eyeball (which is more oval than round) or a cornea which is curved too steeply. The increased length of the eye or the steep curve of the cornea causes the light rays to be focused in front of the retina.
What is Hyperopia?
Hyperopia, or farsightedness, is a common vision problem, affecting about a fourth of the population. People with hyperopia can see distant objects very well, but have difficulty seeing objects that are up close. This vision problem occurs when light rays entering the eye focus behind the retina, rather than directly on it. The eyeball of a farsighted person is shorter than normal. Many children are born with hyperopia, and some of them "outgrow" it as the eyeball lengthens with normal growth.
Monovision
If you are a nearsighted laser candidate, then monovision may be for you. Monovision is a technique in which the doctor fully treats one of your eyes, usually your dominant eye, for distance vision. The doctor then under corrects your non-dominant eye, or does not treat it at all (depending on your initial prescription). This leaves the eye slightly myopic for improved reading vision. Monovision lets you maintain your reading vision in one eye, which may help you to avoid reading glasses once you develop presbyopia. As always, you must give up a little distance sharpness to gain this near vision.
Summary of Laser Vision Correction