Soft lenses are made from gel-like, water-containing plastics called hydrogels. These lenses are very thin, pliable, and conform to the front surface of the eye. Silicone Hydrogel is an advanced type of soft contact lenses that are more porous than regular hydrogel lenses and allow even more oxygen to reach the cornea.
Soft lenses are classified by wearing time:
Daily wear — Must be removed nightly
Extended wear — Contact lenses are available for overnight or continuous wear ranging from one to six nights or up to 30 days. The length of continuous wear depends on lens type and evaluation of your tolerance for overnight wear. It’s important for the eyes to have a rest without lenses for at least one night following each scheduled removal.
Contact Lens Designs
Soft contact lenses (both standard hydrogel and silicone hydrogel lenses) are available in a variety of designs, depending on their intended purpose:
Spherical contact lenses
Spherical Lenses have the same lens power throughout the entire optical part of the lens to correct myopia (nearsightedness) or hyperopia (farsightedness).
Toric soft contact lenses
These types of lenses have different powers in different meridians of the lens to correct astigmatism as well as nearsightedness or farsightedness.
Multifocal contact lenses
Multifocal lenses (including bifocal contacts) contain different power zones for near and far vision to correct presbyopia as well as nearsightedness or farsightedness. Some multifocal lenses also can correct astigmatism.
Cosmetic contact lenses
Include color contacts designed to change or intensify your eye color. Halloween, theatrical, and other special-effect contacts also are considered cosmetic lenses. A contact lens prescription is required for cosmetic contacts even if you have no refractive errors that need correction.
Contact Lens Wear and Care
Cleaning, disinfecting, storing, and Caring for your soft contact lenses—is much easier than it used to be.
A few years ago, you would have needed several different bottles of cleaning products, and perhaps enzyme tablets, for proper care. Today, most people can use "multipurpose" solutions — meaning that one product both cleans and disinfects and is used for storage.
People who are sensitive to the preservatives in multipurpose solutions might need preservative-free systems, such as those containing hydrogen peroxide. Hydrogen Peroxide contacting solutions do an excellent job of cleaning contacts, but it's very important to follow the directions for using them. The solution should not come into contact with your eyes until soaking is complete and the solution is neutralized.
Of course, you can avoid lens care altogether by wearing daily disposable contact lenses.
Lens Replacement Frequency
Daily disposable lenses — Discard after a single day of wear
Disposable lenses — Discard every two weeks, or sooner
Frequent replacement lenses — Discard monthly