Contact Lenses
Don't like wearing eyeglasses?
Don’t want to wear glasses? Contact lenses are a great alternative. With so many varieties to choose from, nearly everyone can wear them. Daily disposable soft contact lenses make wearing contacts a breeze — wear them once and throw them away. Bo-weekly and monthly contact lenses are also available.
Other options include gas permeable contact lenses, lenses for overnight wear, coloured and cosmetic effect contact lenses. Read on to learn more about contact lenses and visit an eye care professional to determine how to choose the best contacts for your lifestyle and visual needs.
Contact Lens Materials
The first choice when considering contact lenses is which lens material will best satisfy your needs. There are five types of contact lenses, based on type of lens material they are made of:
- Soft lenses are made from gel-like, water-containing plastics called hydrogels. These lenses are very thin and pliable and conform to the front surface of the eye. Introduced in the early 1970s, hydrogel lenses made contact lens wear much more popular because they typically are immediately comfortable. The only alternative at the time was hard contact lenses made of PMMA plastic (see below). PMMA lenses typically took weeks to adapt to and many people couldn’t wear them successfully.
- Silicone hydrogel lenses are an advanced type of soft contact lenses that are more porous than regular hydrogel lenses and allow even more oxygen to reach the cornea. Introduced in 2002, silicone hydrogel contact lenses are now the most popular lenses prescribed in North America.
- Gas permeable lenses — also called GP or RGP lenses — are rigid contact lenses that look and feel like PMMA lenses (see below) but are porous and allow oxygen to pass through them. Because they are permeable to oxygen, GP lenses can be fitted closer to the eye than PMMA lenses. This makes them more comfortable than conventional hard lenses. Since their introduction in 1978, gas permeable contact lenses have essentially replaced nonporous PMMA contact lenses. GP contacts often provide sharper vision than soft and silicone hydrogel contacts — especially if you have astigmatism. It usually takes some time for your eyes to adjust to gas permeable lenses when you first start wearing them, but after this initial adaptation period, most people find GP lenses are as comfortable as hydrogel lenses.
- Hybrid contact lenses are designed to provide wearing comfort that rivals soft or silicone hydrogel lenses, combined with the crystal-clear optics of gas permeable lenses. Hybrid lenses have a rigid gas permeable central zone, surrounded by a “skirt” of hydrogel or silicone hydrogel material. Despite these features, only a small percentage of people in the U.S. wear hybrid contact lenses, perhaps because these lenses are more difficult to fit and are more expensive to replace than soft and silicone hydrogel lenses.
- PMMA lenses are made from a transparent rigid plastic material called polymethyl methacrylate (PMMA), which also is used as a substitute for glass in shatterproof windows and is sold under the trademarks Lucite, Perspex and Plexiglas. PMMA lenses have excellent optics, but they do not transmit oxygen to the eye and can be difficult to adapt to. These (now old-fashioned) “hard contacts” have virtually been replaced by GP lenses and are rarely prescribed today.
Contact Lens Wearing Time
There are two types of classified contact lens 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 term that’s sometimes used to describe 30 consecutive nights of lens wear — the maximum wearing time approved by the FDA for certain brands of extended wear lenses.
When To Replace Your Contact Lenses
Even with proper care, contact lenses (especially soft contacts) should be replaced frequently to prevent the build-up of lens deposits and contamination that increase the risk of eye infections.
Soft lenses have these general classifications, based on how frequently they should be discarded:
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 or quarterly
- Traditional (reusable) lenses — Discard every six months or longer
Gas permeable contact lenses are more resistant to lens deposits and don’t need to be discarded as frequently as soft lenses. Often, GP lenses can last a year or longer before they need to be replaced.
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 have the same lens power throughout the entire optical part of the lens to correct myopia (nearsightedness) or hyperopia (farsightedness).
- Toric soft contact lenses have different powers in different meridians of the lens to correct astigmatism as well as nearsightedness or farsightedness. Read more here: toric contact lenses.
- Multifocal contact 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. Read more here: bifocal contacts.
- Cosmetic contact lenses include colour contacts designed to change or intensify your eye color. Halloween, theatrical and other special-effect contacts are also considered cosmetic lenses. A contact lens prescription is required for cosmetic contacts even if you have no refractive errors that need correction.
All of these lenses can be custom made for hard-to-fit eyes. Other lens designs are also available — including scleral lenses that are fabricated for use in special situations, such as correcting for keratoconus.
More Contact Lens Types, Designs & Features
Bifocal contacts for astigmatism. These are advanced soft contacts that correct both presbyopia and astigmatism, so you can remain glasses-free after age 40 even if you have astigmatism. Learn more here: bifocal contact lenses for astigmatism.
Contacts for dry eyes. Are your contacts uncomfortably dry? Certain soft contact lenses are specially made to reduce the risk of contact lens-related dry eye symptoms. Learn more here: contact lenses for dry eyes.
Coloured lenses. Many of the types of lenses described above also come in colours that can enhance the natural colour of your eyes — that is, make your green eyes even greener, for example. Other coloured lenses can totally change the color of your eyes, as in from brown to blue.
Special-effect lenses. Also called theatrical, novelty, or costume lenses, special-effect contacts take colouration one step further to make you look like a cat, a vampire, or another alter-ego of your choice.
Prosthetic lenses. Coloured contact lenses also can be used for more medically oriented purposes. Opaque soft lenses called prosthetic contacts can be custom-designed for an eye that has been disfigured by injury or disease to mask the disfigurement and match the appearance of the other, unaffected eye.
Custom lenses. If conventional contact lenses don’t seem to work for you, you might be a candidate for custom contact lenses that are made-to-order for your individual eye shape and visual needs.
UV-inhibiting lenses. Some soft contact lenses help protect your eyes from the sun’s ultraviolet rays that can cause cataracts and other eye problems. Since contacts don’t cover your entire eye, you still should wear UV-blocking sunglasses outdoors for the best protection from the sun.
Scleral lenses. Large-diameter gas permeable lenses called scleral contacts are specially designed to treat keratoconus and other corneal irregularities, as well as presbyopia.
Myopia control contacts. Special contact lenses are being developed to slow or stop the progression of nearsightedness in children. Learn more here: myopia control.
Which Contact Lens Is Best for You?
- Your contacts must address the problem that is prompting you to wear lenses in the first place. Your contact lenses must provide good vision by correcting your myopia, hyperopia, astigmatism, or some combination of those vision problems.
- The lens must fit your eye. Lenses come in different combinations of diameter and curvature and not every lens brand comes in every “size.”
Your eye care professional (ECP) is licensed and skilled in evaluating your eye’s physiology, and your eyesight or prescription, to determine which lens best satisfies the fit and visual needs. - You may have another medical need that drives the choice of lens. For example, your ECP might pick a particular lens if your eyes tend to be dry.
Finally, consider your “wish list” of contact lens features — colours, for example, or overnight wear. When you and your ECP decide on the right lens for you, you’ll be given trial contact lenses, contact lens prescription and a follow up exam. You’ll be able to buy a supply of lenses from your ECP.
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. People who are sensitive to the preservatives in multipurpose solutions might need preservative-free systems, such as those containing hydrogen peroxide. These 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.
Contact Lens Problems
Trial and error often is involved in finding the perfect lens for you. People react differently to various lens materials and cleaning solutions. Also, the correct “parameters” of your lens — that is, power, diameter, and curvature — can be finalized only after you’ve successfully worn the lens. This is especially true for more complex fits involving extra parameters, such as with bifocals or toric contact lenses for astigmatism.
If you experience discomfort or poor vision when wearing contact lenses, speak to your eye care professional and chances are that an adjustment or change of lens can help. Today, there are more contact lens choices available to provide comfort, good vision, and healthy eyes. If your eyes or lenses are uncomfortable or you are not seeing well, remove your lenses and visit your eye care professional to explore available remedies for contact lens discomfort.
Source: https://www.allaboutvision.com/contacts/contact_lenses.htm