Most vision problems occur when the eye cannot focus the image onto the retina. Here are a few of the most common problems:
- Myopia (nearsightedness)
- Hyperopia (farsightedness)
In nearsightedness (myopia), the light from distant objects gets focused in front of the retina rather than on it. Myopia happens usually when the eyeball is too long; however, it is sometimes caused by too much focusing power in the lens system. The result is that the person can see close-up objects clearly, but distant objects are blurry.
In farsightedness (hyperopia), the light gets focused in back of the retina rather than on it. Hyperopia usually happens when the eyeball is too short or when the focusing power of the lens system is too weak. The result is that a person can see distant objects clearly, but close-up objects are blurry.
In astigmatism, the shape of the cornea or the lens is distorted so that the light comes into two focal points. Imagine that the lens is egg-shaped instead of spherical, and that light coming over the top and bottom edges is brought to a different focal point than light coming over the right and left sides.
In presbyopia, the cornea and lens of the eye become less stretchy, and therefore cannot change shape as readily to bring light to a focus on the retina; this happens naturally as we grow older and is usually observed when people reach their 40s. If you have presbyopia, you have trouble focusing light from near objects on the retina. To correct this problem, you might get a pair of bifocal lenses to replace your existing glasses. If you don't already wear corrective lenses, you may be able to simply use reading glasses.
LASIK is very effective in treating myopia and, in many cases, can correct vision problems resulting from astigmatism and hyperopia as well. However, presbyopia is not easily corrected through the use of laser eye surgery.
Let's take a look at exactly what LASIK is and you'll understand why it works so well for myopia.