So far, around 125 million people all over the world use contact lenses. As opposed to glasses, contact lenses don't fog up, are not affected by wet weather and provide a wider field of vision (with regular glasses, you hardly have peripheral vision at all).

But contact lenses are not just that. If you visit your eye doctor and have some prescribed for you, you will find out that there are actually various kinds around, depending on your requirements. They differ in terms of function, material, shape, disposability, number of focal points and wear periods.

Functions of contact lenses

Contact lenses have three basic uses: cosmetic, corrective and therapeutic.

Corrective contact lenses are made to help improve vision. Such kinds of lenses neutralize refraction discrepancies in the eye, that is, the lack of balance between the eye's length and its refractive abilities. Corrective contact lenses usually address problems like near/short sightedness and far sightedness, presbyopia and astigmatism.

Cosmetic contact lenses are made to, well, change your eye's appearance, whether it's for an aesthetic reason or for theatrical/costume-related purposes. They come in different styles and designs. Because they are cosmetic, not all can correct vision. Some of them, depending on the complexity of the prints, can even obstruct or blur vision.

Therapeutic contact lenses, or soft lenses, are commonly used to help in the healing of certain eye-related surgeries and treatments. Some of the treatments such contact lenses are used in are corneal ulcers, dry eyes, corneal edema and keratitis.

The different makes of contact lenses

When contact lenses first came into the market, they were initially made of glass. It was eventually phased out because they caused eye irritations and were not made for longer use. They were replaced by contact lenses made of PMMA or plexiglas, which were easier and lighter to wear. They are commonly called "hard lenses".

However, soft contact lenses are more often used nowadays. They are made of silicone hydrogels, which have high oxygen permeability, so your eyes don't tire out easily and feel suffocated. Soft contact lenses are normally used for extended or overnight use.

How long can you wear contacts?

It varies. Extended wear contact lenses may be used overnight or for a couple of days (to as long as a month, for continuous wear lenses), while there are some contact lenses that have to be put on and taken out everyday. Also, contact lenses differ based on disposability. This means, there are some lenses that are designed just for single use, others need to be changed after a few months, while others can last up to a year or so.

Contact lenses are taken cared of using a special cleaning solution available in all optical shops and pharmacies. These solutions will help take out the dirt in your contacts, particularly the proteins that have lodged themselves in during use. Some contact lense solutions work with just one washing, while there are others that require your lenses to be soaked for a particular amount of time.

Once you have decided to get contact lenses for yourself, always keep in mind that your vision is one of your greatest indispensable assets. So you should take of this gift by choosing only the best and doctor-prescribed products for your eyes.