Contact lesnes and the various types available

Introduction to Contact Lenses

Contact lenses, also sometimes casually just called contacts, are thin lenses that are made of glass or plastic. They are fitted to the eyeball to correct vision. They are a great choice for people who do not like the look of spectacles. In the United State, thirty million people are wearing contact lenses.

If you can tolerate wearing them contacts are a convenient choice for people who do not want to wear glasses. They do not slip off your face or steam up or hamper your vision. They also do not pinch your nose or the back of the ears.

Wearing contact lenses does come with some drawbacks. Contacts can stop the flow of tears. Tears are necessary to cleanse the eyes. Every year it seems that the manufacturers of contact lenses come up with lenses that are more permeable to oxygen so that these drawbacks are less common.

History

Contact lenses were first introduced in the late nineteenth century. They were crude and made of glass. These lenses fit over the entire eye and were called the sclera.

In the 1930s safer contact lenses were developed that were made from polymethyl methaclyrate. However the every day use of contact lenses did not take off until the 1950s when contact lenses that only covered the cornea were invented. These were easier to fit and allow a better exchange of oxygen and tear.

Old-fashioned scleral lenses are rarely worn except for those with special afflictions of the eye surface such as sever karatoconus. Most lenses nowadays are semi-scleral or corneal lenses.

Modern lenses are made from two types of plastics, rigid gas permeable (RGP) and silicon-gel plastic.

Applications

Contact lenses can remedy all kinds of different refractive disorders such as astigmatism and far sightedness. They can also be of some assistance in improving the vision of individuals with non-refractive disorders such as cataracts and glaucoma. Some types of therapeutic contact lenses are used to protect the eyes after they have had surgeries. There is also a type of contact lens available on the commercial market that is simply developed to change the color of the eyes.

Types of contact lenses

Most contacts are made of silicon gel material. These are called soft contacts. There is another type called RPG, which stands for rigid gas permeable contacts.

Soft contact lenses

Soft contact lenses are worn by about 75% of the contact lens wearers today. They have a high percentage of water, which makes them soft, flexible and comfortable to wear.

The following is a summary of the different types of contacts that are commercially available –

• Daily wear contact lenses: These are an economical choice because you clean the same pair every day. It is not advised that you wear them when you are asleep. If cleaned well they should last at a year. One problem with these is that protein deposits can sometimes build up on them.
• Disposable contacts: These are a hygienic choice because you just wear them and then throw them away. Depending on the kind of contacts that you choose, they are used for periods ranging from one day to three months. They reduce your risk of eye infection.
• Extended wear contacts: These contacts are manufactured from permeable silicon hydrogel which allows you to sleep with them in your eyes. Depending on the type of lenses you choose you wear them every day for a week or thirty days. Silicon contact lens has fewer complications than other kinds.

RGP lenses

RGP lenses (rigid gas permeable lenses) are used to correct all types of vision problems including astigmatism. They made from stiffer material than silicon or gel lenses and therefore may be harder to adjust to. However they have high oxygen permeability and have a very low risk of corneal infections. They also last longer than soft contacts and can last two or three years before having to be replaced.

Lenses for astigmatism

There are lenses that have developed specifically for astigmatism called toric lenses, These are available in RGP and soft contact versions. The difference is that the lenses have a special surface that corrects astigmatism.

Contact lens complications

The fact that contact lenses block the normal flow of oxygen to the cornea means that wearing them can cause complications. However there are some measures that can be taken to prevent this.

Cleaning ritual

Cleaning non-disposable lenses regularly is vital not only for the lenses but also for your eyes. Many complications from wearing contact lenses can be prevented by keeping the lenses clean.