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Contact lens basics: Types of contact lenses and more.

ontact lenses are an excellent choice for nearly anyone who needs vision correction and doesn't want to wear eyeglasses full time or undergo LASIK surgery.

Unsure about contact lenses? This article will detail contact lens materials, contact lens designs and features and even new contact lens formats.

For instance, the first light-adaptive contact lenses, Acuvue Oasys with Transitions , debuted in the United States in 2019 and contact lenses embedded with antibiotics are in the works. (See our contact lens news page for the latest in contact lenses.)

Here are the basics you should know about contact lenses before seeing your eye doctor if you are interested in wearing contacts.

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:

Contact Lens Material

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 the United States.
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 fit closer to the eye than PMMA lenses, making 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.

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Caring for your soft contact lenses

Enter the contact lens care aisle of most supermarkets and drugstores, and you'll find a confusing array of products.

Though daunting, it's essential to understand lens care: Not caring for your contact lenses properly can lead to a variety of eye infections, including some that cause blindness.

Actually, contact lens care is easier than ever. One-bottle care systems and disposable contact lenses mean that proper lens care involves much less time, expense and trouble than it did years ago.

Before we get started, understand that you should not switch care regimens without asking your eye doctor first. Some products are not compatible with each other, or with certain contact lenses. Using incompatible products can ruin your contact lenses or harm your eyes.

To make sense of all the bottles and boxes, it helps to know what steps are required to care for soft contacts.

It's particularly important to follow guidelines for safe handling of soft contact lenses in light of recent outbreaks of serious fungal eye infections associated with a popular (now discontinued) brand of contact lens cleaning/disinfecting solution.

he Basics Of Soft Contact Lens Care: Clean, Rinse And Disinfect

To clean contacts with a multipurpose solution, place the lens in the palm of your hand, apply a generous amount of solution and gently rub the lens against your palm with your pointer finger, using a back-and-forth (not circular) motion.

Wash your hands so that you don't transfer dirt and germs to your eye. Try to avoid moisturizing soaps, as they are not good for contact lenses. Dry your hands with a lint-free towel.
Remove one lens and clean it with the recommended solution. Cleaning removes eye-produced buildup, cosmetics and other debris that impairs lens comfort. The
FDA

recommends that you rubthe lens in the palm of your hand with a few drops of solution, even if you are using a "no-rub" product.
Rinse the lens again to remove the loosened debris, making sure to take as long as the package directs: Rinsing is an important step.
Place the lens in your clean lens case or lens holder and fill with fresh solution; don't "top off" your old solution. Disinfecting kills microorganisms on the lens. Disinfection time varies from product to product; check the package for details.
Repeat steps two through four for your other lens.

Beyond Clean, Rinse And Disinfect

Protein. Depending on what kind of contact lenses you wear and how much protein

your eyes deposit on your contacts, your doctor may recommend you use a product for protein removal.

While cleaning them does remove some protein, it can still build up on your lenses and make them uncomfortable. That's why the longer you wear lenses before replacing them, the more likely you are to need a protein remover.

For example, if you wear disposables, you probably won't need one; but if you wear the kind of lenses that are replaced only once or twice a year, you definitely will. Products for removing protein include enzymatic cleaner and daily protein removal liquids.

Eye dryness and irritation. Use contact lens eye drops to lubricate your eyes and rewet your lenses.

Eye sensitivity and allergies. A small percentage of lens wearers develop an eye allergy to the chemicals present in contact lens solutions. If this is the case with you, you don't need an additional product: You just need to switch products to those marked "preservative-free."

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UV and sunglasses: How to protect your eyes

You probably know that too much exposure to the sun's ultraviolet (UV) rays can cause sunburn and skin cancer. But did you know UV also can harm your eyes?

Extended exposure to the sun's UV rays has been linked to significant eye problems, including cataracts, macular degeneration, pingueculae, pterygia and photokeratitis

Protecting your eyes from UV

To protect your eyes from harmful solar radiation, you should wear sunglasses that block 100 percent UV whenever you are outdoors in daylight. Your eyes need protection even on cloudy days because the sun's damaging UV rays can penetrate cloud cover.

Sunglass frames with a close-fitting wraparound

style provide the best protection because they limit how much sunlight reaches your eyes from all sides.

What is UV?

Ultraviolet (UV) rays are higher in energy and do not fall within the realm of visible light, as shown here. In the electromagnetic spectrum, radio waves have the lowest energy, and gamma rays have the highest energy.

While many people refer to ultraviolet radiation as "UV light," this term technically is incorrect because you cannot see UV rays. Ultraviolet radiation is invisible.

There are three categories of UV radiation:

UVC

These are the highest energy UV rays and potentially could be the most harmful to your eyes and skin. Fortunately, the atmosphere's ozone layer blocks virtually all UVC rays.

But this also means depletion of the ozone layer potentially could allow high-energy UVC rays to reach the Earth's surface and cause serious UV-related health problems.

UVC rays have wavelengths that range from 100 to 280 nanometers (nm).

UVB

UVB rays have slightly longer wavelengths (280-315 nm) and lower energy than UVC rays. These rays are filtered partially by the ozone layer, but some still reach the Earth's surface.

In low doses, UVB radiation stimulates the production of

(a skin pigment), causing the skin to darken, creating a suntan.

But in higher doses, UVB rays cause sunburn that increases the risk of skin cancer. UVB rays also cause skin discolorations, wrinkles and other signs of premature aging of the skin.

Overexposure to the sun's UVB radiation also is associated with a number of eye problems, including pinguecula, pterygium and photokeratitis ("snow blindness").

Because the cornea appears to absorb 100 percent of UVB rays, this type of UV radiation is unlikely to cause cataracts and macular degeneration, which instead is linked to UVA exposure (see below).

UVA

UVA rays are closer to visible light rays and have lower energy than UVB and UVC rays. But UVA rays can pass through the cornea and reach the

lens and retina inside the eye.

Overexposure to UVA radiation has been linked to the development of certain types of cataracts, and research suggests UVA rays may play a role in development of macular degeneration.

Source:

https://www.allaboutvision.com/sunglasses/spf.htm

Computer glasses: Relieving computer eye strain

When you work at a computer for any length of time, it's common to experience eye strain, blurred vision, red eyes and other symptoms of computer vision syndrome (CVS). This is because the visual demands of computer work are unlike those associated with most other activities.

If you're under age 40, eye strain or blurred vision during computer work may be due to an inability of your eyes to remain accurately focused on your screen or because your eyes have trouble changing focus from your keyboard to your screen and back again for prolonged periods. These focusing (

) problems often are associated with CVS.

If you're over age 40, the problem may be due to the onset of presbyopia — the normal age-related loss of near focusing ability. This, too, can cause CVS symptoms.

What can you do? For starters, have a comprehensive eye exam to rule out vision problems and update your eyeglasses prescription. Studies show that even small inaccuracies in your prescription lenses can contribute to computer vision problems.*

If your glasses are up-to-date (or you don't need prescription eyewear for most tasks) and you continue to experience eye discomfort during computer work, consider purchasing customized computer glasses. These special-purpose glasses are prescribed specifically to reduce eye strain and give you the most comfortable vision possible at your computer.

Source:

https://www.allaboutvision.com/cvs/computer_glasses.htm