Contact Lenses – Material and Types

What your contact lenses are made of affects how they wear in many senses of the word, including how long they last, your comfort and their health impact. For many years contact lenses were made of glass. Today, fewer than 1% are, with the other 99% made from various types of plastic. The choices are predominantly some type of PMMA (polymethyl methacrylate), polycarbonate or silicon hydroxy gel.

Hard contact lenses introduced in the 1960s are made of PMMA and don’t allow oxygen to move directly through the lens, but some air does reach under it anyway. When a person blinks the lens moves slightly and some air diffuses through the tear solution that covers the eyeball.

Soft contact lenses, first introduced in 1971, were made of a polyacrylamide containing nitrogen (hydroxyethyl methacrylate or HEMA) which made them what is called ‘hydrophilic’. This ability to absorb water makes them flexible, and therefore more comfortable. At the same time, they are slightly more permeable to air than their older cousins.

RGP (Rigid Gas Permeable) lenses are midway between a truly hard lens, like glass or PMMA, and a soft lens. They combine PMMA with silicone and fluoropolymers that allow air to get to the eye. That increases your comfort and reduces the odds of health problems due to long-term wear.

Extended wear lenses, which come in anywhere from 2-day to 7-day to even 30-day use models, are made of silicon hydroxy gel. That material allows up to seven times the amount of oxygen to pass through the lens, making it possible to wear them longer than others.

Disposable contact lenses, first introduced in 1987, have now become extremely popular. They can be worn daily for a week or two and removing them every night is an option. Most are designed to be worn continuously then simply thrown away. Made from a combination of a polymer called etafilcon (42%) and water (58%), they’re very thin, flexible and have excellent gas permeability.

Disposables are especially popular among sports enthusiasts because of the fact that they fit close to the eye, making them very difficult to dislodge. They’re also very comfortable, so they can be easily ignored during activity. However, many don’t offer quite the level of crystal clear vision as other types, so they’re not suitable for everyone. Also, they don’t correct some vision problems as well as other types, which limits their use for some.

Apart from the choice of material and wear characteristics, there are several options today in contact lenses that simply didn’t exist 20 years ago.

Single vision lenses are like a pair of glasses worn close to the eye. They were once the only choice. Today, bifocals in contact lenses are possible. Even multifocal or progressive lenses are an option. These help compensate for presbyopia, a type of farsightedness that affects nearly everyone as they age, typically beginning in the mid-40s.

Investigate your options with your eye care professional and you’ll soon find a pair of contact lenses just right for you and your lifestyle.

Disposable Contact Lenses

Disposable contact lenses first appeared on the market in 1987. Since then they have become one of the most popular options for contact lens wearers. They’re comfortable, safe and come in a variety of different types.

Disposables are designed to be worn and discarded either daily, weekly, bi-weekly or monthly. But it’s important to keep in mind a distinction, that between the replacement schedule and the wear schedule. Some are designed to be worn daily and discarded daily. But some that are labeled dailies are removed daily, cleaned and stored, then reused up to their intended lifetime. That lifetime can be one week, two weeks, or even as long as a month. Make sure you note which is which when you choose your lenses.

The more often you change your contacts the lower the odds of health problems. Even the best of contacts reduce the amount of oxygen that gets to the surface of the cornea. That increases the chances of suffering an infection. Longer wear cycles also increase the odds of corneal abrasion, conjunctivitis and other eye health issues.

However, changing lenses more frequently can increase the odds of introducing other kinds of health problems. One example would be where some wearers can suffer an allergic reaction to the preservative solutions used with contact lenses. Wearing a pair of disposables continuously for a week, then simply throwing them away, eliminates that possibility. They come packaged in a sterile solution, so they never need to be cleaned unless they’re removed and re-inserted.

Convenience is a huge factor in disposables, not surprisingly. The daily ritual of the insertion and removal of the lenses still necessitates sterilization and cleaning. While many contact lens wearers establish a routine, others find the practice something they would prefer to avoid. Disposables offer that option. Many are designed for single use and then discarded. Many types of extended wear disposables can stay in overnight, or a week, or even up to a month.

Since those are inserted only once, they never need to be cleaned or sterilized at all. You just clean your hands, insert them, then throw them away after the wear period. No muss, no fuss. But, that convenience comes at a price.

Cost of course is a factor that has to be considered and the cost is not always small. While prices vary over time, disposable contact lenses are typically more expensive over the long run. You pay for the convenience. However the cost per day is lower as the contacts are only intended for use over short periods of time.

One way manufacturers can do that, of course, is to use different materials and production methods. The result is a safe, comfortable lens but one that may not provide the same optimally sharp vision that another style can.

Still, many sports enthusiasts enjoy disposables thanks to their tight fit, which results in them being very hard to knock loose. And if the quality is good enough for them, it will probably be good enough for most everyone.

Investigate your options in disposable contact lenses and you may well find one that is just right for you and your lifestyle.