Contact Lenses Basics
Contact lenses can correct your nearsightedness, farsightedness and astigmatism
Contact lenses can also provide a full field of unobstructed vision, which is great for sports.
If you’re new to contact lenses, your first step is to see an eye doctor. They must be prescribed and properly fitted by an ophthalmologist. Your doctor will evaluate your visual needs, your eye structure, and your tears to help determine the best type of lens for you.
The many types of contact lenses currently available can be grouped in various ways according to:
What they’re made of
How long you wear them without removal
How often you dispose of them
The design of the lens
Contact Lens Materials
Classified by material, there are three types of contact lenses:
Hard lenses are made from PMMA. These lenses are virtually obsolete and rarely used.
Soft lenses are made from gel-like, water-containing plastics, and are most common. They’re a bit larger in size than your iris (the colored part of your eye).
GP lenses, also known as RGP or “oxygen permeable” lenses, are made from rigid, waterless plastics and are especially good for presbyopia and high astigmatism. These lenses are usually about eight millimeters in diameter, which is smaller than your iris.
Recently, new silicone hydrogel contact lenses have been introduced. They have become the contact lenses of choice for many eye care practitioners, because they allow more oxygen to pass through the lens to the eye, and they are less prone to dehydration.
Contact Lens Wearing Time
Now, two types of lenses are classified by wearing time:
Daily wear – must be removed nightly
Extended wear – can be worn overnight, usually for seven days consecutively without removal
“Continuous wear” is a type of extended wear lens that can be worn for 30 consecutive nights.
Disposal Intervals for Contact Lenses
One problem with soft contact lenses is that proteins and lipids – which are naturally found in tears – adhere to the surface of the lens, sometimes causing discomfort and providing hiding places for infection-causing germs.
Lens-cleaning products help. But over time buildup still occurs, necessitating lens replacement. Disposable lenses, first introduced in 1987, address this problem in different ways. Here are the options:
Daily disposable – replaced every day
Disposable (used for daytime wear) – replaced every two weeks
Disposable (used for overnight wear) – replaced every week
Continuous wear (used for 30-day wear) – replaced monthly
Planned replacement – replaced monthly or less frequently
Contact Lens Designs
Many lens designs are available to correct various types of vision problems:
Spherical contact lenses are the typical, rounded design of contact lenses, which can correct myopia (nearsightedness) or hyperopia (farsightedness).
Bifocal contact lenses contain different zones for near and far vision to correct presbyopia, which is the age-related, decreased ability to obtain a full range of vision
Orthokeratology lenses are specially designed to reshape the cornea during sleep, providing lens-free daytime wear
Toric contact lenses correct for astigmatism, as well as for myopia and hyperopia All of these lenses can be custom made for hard-to-fit eyes. Many other additional lens designs are available. Typically these are less common and fabricated for use in special situations, such as correcting for keratoconus.
Colored Lenses. Many of the types of lenses described above also come in colors that can enhance the natural color of your eyes – that is, make your green eyes even greener, for example. Or these lenses can totally change the eye’s appearance, as in from brown to blue.
Prosthetic Lenses. Colored contact lenses can also be used for more medically oriented purposes. People with disfigured eyes, as a result of accidents or disease, can use a custom, opaque colored lens to mask the disfigurement and match the appearance of their normal eye
Custom Lenses. If conventional contact lenses don’t seem to work for you, you might be a candidate for a customized design.
UV-Inhibiting Lenses. Today, many contacts incorporate an ultraviolet blocker in the lens material, to cut down on UV light that can eventually cause cataracts and other eye problems. You can’t see this blocker by looking at the lens. And since contacts don’t cover your entire eye, UV blockers cannot substitute for traditional sun protection like good quality sunglasses.
Hybrid Lenses. One brand of lenses features a GP center with a soft outer skirt, providing wearers with both the crisp optics of a rigid lens and the comfort of a larger, soft lens.
Contact Lens Wear and Care
Caring for your contact lenses: cleaning, disinfecting and storing them is much easier than it used to be.
Today, most people can use “multipurpose” solutions – meaning that one product both cleans and disinfects, and is used for storage. Some people who are sensitive to the preservatives in multipurpose solutions might need preservative-free systems, such as those containing hydrogen peroxide.Of course, you can avoid lens care altogether by using daily disposables.
Contact Lenses and UV Light
Researchers have linked ultraviolet (UV) light to the formation of cataracts. Exposure to excessive UV light also may result in a condition called photokeratitis.
That’s why some lenses now incorporate a UV-blocking agent. You can’t tell if a contact lens has a UV blocker just by looking at it – the blocker is provided in clear form, so as not to disturb vision. The contact lens packaging will specify if the product has a UV blocker, or you can ask your eye doctor.
Very important: UV-blocking contacts are not meant to replace sunglasses. A contact lens covers only your cornea, not your entire eye.
However, UV-blocking contact lenses do help protect the portion of the white of your eye that is covered from formation of growths such as pingueculae and pterygia.
Sunglasses with UV protection can cover more of your eye and the parts of your face that surround the eye, depending on the size of the sunglass lens. That’s why contacts with UV blockers are designed to complement sunglass use as an added protection.