If you need to sharpen your vision, you have many options to choose from among eyeglasses, contact lenses or the increasingly popular refractive surgery (sometimes referred to as laser vision surgery). A wide variety of lens treatments and eyeglass frames are available - from lightweights for comfort and style to sturdy goggles for playing contact sports. Contact lenses come in rigid and soft styles, which allows you to select a pair that suits your lifestyle and the sensitivity of your eyes. If you prefer not having to deal with corrective lenses at all, you may choose to have your vision corrected surgically. Two surgical options that are especially popular are LASIK and PRK. These acronyms will be explained, along with details of each procedure, in future posts.
 |
| Lasik Vision Correction Surgery |
You and your eye doctor can decide which of these options is best for you. You'll certainly want to take your individual needs into consideration. If your lifestyle or health keeps you from being especially active, glasses may be your best choice. If you're on the go a lot or don't like the look and feel of glasses, you may prefer contacts or the more permanent solution of surgery. Your choices may narrow once you understand a bit about how corrective lenses function and the key differences among the various options.
How corrective lenses correct vision
With normal vision your cornea and lens refract (bend) light that passes through them to focus a sharp image on the retina. If your eyeball is too long or too short from front to back, the image won't be as sharply focused as it should be. The point of focus will lie a little in front of or in back of your retina, blurring the image. A distortion in the curvature of your cornea or lens can also blur vision.
For example, the cornea may be more steeply curved from left to right than from top to bottom. The way you can correct these types of vision problems without surgery is by looking through a custom-built lens that compensates for any error in the shape of your eye or the curvature of your cornea or lens. The three basic shapes for corrective lenses are convex, concave and cylindrical.
The refractive power that a corrective lens needs to counteract your specific vision problem is based on the prescription you get from a routine eye exam. The prescription number determines the shape and thickness of your lens. For example, the thickness of a concave lens can vary considerably, depending on whether you are very nearsighted or slightly nearsighted. The higher the prescription number, the stronger the prescription - meaning the more light that must be refracted, the thicker the lens needs to be.
How to read your eyeglasses prescription
The following example demonstrates how to interpret the numbers and abbreviations of a typical prescription for corrective lenses:
Sphere Cylinder Axis
OD -2.75 -2,25 90
SD -1.75 -2.00 90
+1.50 add
- OD (oculus dexter) is your right eye, identified on some prescriptions as RE.
- OS (oculus sinister) is your left eye, sometimes listed as LE.
- Sphere is the correction measurement for your nearsightedness or farsightedness.
- Cylinder is the correction measurement for astigmatism.
- Axis shows where the astigmatism correction should be on the lens - the position in degrees from horizontal. It can be anywhere from 1 to 180 degrees, with 90 degrees being a vertical (up-and-down) line.
- The term +1.50 add at the bottom of the chart refers to an additional lens, in this case, bifocals for close work.
 |
| Lasik Vision Correction Surgery |
A person wearing lenses with the prescription given above is nearsighted, meaning the lenses are concave. That's why the diopters are preceded by a minus sign. On a prescripion to correct farsightedness, the numbers would be preceded by a plus sign. The lenses would be convex. To find out more, you can check out Lasik Vision Correction Surgery.