The first thing you need to know is that contact lenses are made of a variety of plastics, but it is broadly divided into two; Soft and Rigid Gas Permeable (RGP) plastic.

Soft contact lenses comprise up to 80% of water and are very comfortable to wear. Conventional soft contacts last for about a year.

Rigid gas permeable contact lenses are also known as Oxygen Permeable Contact Lenses or GP Lenses. They are made of a combination of silicon and fluorine and don't attract deposits like soft contacts do.

This makes it easier to care for. It can last for several years. However, these can be a little uncomfortable to wear and can take you sometime to get used to it.

What's Available

Here is a quick look at the various types of lenses available in the market.

Daily Wear Soft Lenses

These are made of soft and pliable plastics that allow oxygen to reach the eye. They are very comfortable to wear but are not appropriate for all vision problems.

Plus it requires daily removal and cleaning.

Disposable Soft Lenses

These can be worn for up to two weeks before discarding. It also requires daily cleaning, however comparatively less frequently than daily wear soft lenses.

Daily Wear, Disposable Soft Lenses

These are worn only for a day and then discarded. The advantage being, fresh ones are used every single day and therefore no issues of cleaning or maintaining.

Extended Wear Lenses

These can be worn for up to 30 days without being removed. They are available in both RGP and soft lens format.

Daily Wear RGP Lenses

These provide sharper vision than soft lenses and can be used to correct most vision problems. They are also more durable and easier to care for. However it takes longer to get use to them.

Toric Contact Lenses

These lenses combine cylindrical and spherical components to correct the problem of astigmatism.

Toric contact lenses are made from the same materials as regular contact lenses, so they can be either soft or RGP/GP. The difference is in the design of the lens.

Torics are available as frequent replacement, disposable and even daily disposable lenses.

Bi-Focal Contact Lenses

They work in the same way as your bi-focal glasses. That is, they help correct near and far sight defects.

They come in both soft and firm materials. It is advisable to go for GP lenses as they are flexible and don't shift when you blink. This reduces eye-straining.

It also makes easier to adapt to viewing near and far sights without a "swimming" feeling.

Novelty Lenses

If it is fashion that you are looking for, then these types of lenses fit the bill. They are available in  various designs like cat's eyes, sports team logos, flags, coloured, etc.

So there you go… your crash course in contact lenses. If you are a first timer, visit your optician for an application demo. And remember, your eyes need to get used to lenses, before making it a permanent daily aspect.

(With inputs from Dr. Priya Nambiar, Ophthalmologist, Meenakshi Mission Hospital and Research Centre, Madurai)