Shielding your eyes from UVB rays can delay cataracts, but once they've begun the only cure is surgical lens replacement.
Removing a cataract-clouded lens from an eye and replacing it with an intraocular implant, or IOL, is the most commonly performed surgery in the United States. There were 1.8 million procedures for Medicare recipients alone in 2004. IOLs are also occasionally used to treat extreme refraction errors -- nearsightedness or farsightedness -- or to correct the vision of someone who for a medical or other reason is unable to wear contact lenses or glasses. An IOL permanently replaces the natural lens. Several types are available to suit each patient's vision needs.
Monofocal Intraocular Lens
The basic IOL has been available for decades. It can be calibrated to correct your vision ideally for either close work such as reading or distance vision such as driving, but you might find you still need glasses for the other kind of vision. Another option is to have one eye corrected for distance and one for closer vision, In this arrangement, called "monovision," your brain will quickly learn which eye signal to rely on for the sharpest details of a particular situation, and without losing any of the benefits of binocular (two-eyed) vision, such as depth perception.
Multifocal Lenses
These IOLs are more like bifocals or trifocals, or multifocal contact lenses. They usually have concentric rings with the lens for closest vision in the center and one or more surrounding rings for progressively distant vision. The effect is similar to the way your natural lens gives you precise focus on a word at a single spot on the page you're reading at close range, but allows you to glance up and still see the other side of the room in consistent clarity, although not as precisely as you saw the word on the page.
Accommodative Lenses
Some IOLs actually make use of the muscles in your eye to move the implant closer to or farther from the retina --- just as they did a natural lens --- to adjust the focus more accurately on that signal-gathering surface at the back of your eye.
Toric Lenses for Astigmatism
Because astigmatism is an error in the shape of the cornea, it is not corrected by an intraocular implant unless the implant, like an eyeglass or contact lens, is shaped asymmetrically to compensate. (A torus is a donut shape, though that somewhat overstates the shape of a toric lens.) A toric lens works only if its asymmetry is aligned precisely with that of the cornea, so everything becomes a bit more delicate.
Tags: natural lens, contact lenses, intraocular implant, toric lens, vision such