Kinds of Contact Lenses:

There are several main kinds of contact lenses, and no one is inherently better than any other. A professional should make the decision as to which type of lens is right for you.

Hard Lenses:The oldest kind of contact lens is the rigid “PMMA” lens, which was developed in the United States in the 1950s. These are no longer commonly worn but are still available. They are characterized by their stiffness and their inability to allow oxygen to pass through to the cornea.

RGP lenses, or "rigid gas permeable" lenses are also "hard" but, unlike PMMA lenses, allow oxygen to pass through to the cornea. Because they are hard, they are easier to handle than soft contacts are less likely to tear and last longer. The adjustment period when switching to hard contact lenses may be several weeks long and the contacts themselves may be less comfortable overall.

Soft Lenses:Soft contact lenses are made out of a combination of flexible plastics that are permeable and allow oxygen to pass through to the cornea. Because of their flexibility, soft lenses are more comfortable and easier to adjust.

Extended Wear Contact Lenses:As opposed to disposable lenses, extended wear lenses may be removed and replaced several times. Depending upon the life of the specific lens, some extended wear contact lenses may be re-used for many months and can be worn for days at a time without removal. These contacts are soft and permeable. The increased oxygen flow through these lenses allows them to be worn overnight. An optometrist should specify the length of time over which the contacts can be worn.

Disposable Contact Lenses:Some disposable lenses should be worn for only one day, and then discarded. Other extended wear lenses should be thrown away after several days or even one month. Daily disposable lenses are the most popular and inherently safe form of contact lens, but may incur extra costs for the wearer.

Specialty Contact Lenses:
Orthokerotalogy Lenses:Orthokerotalogy lenses are rigid lenses that are especially designed to physically re-shape the cornea. By correctively altering the shape of the cornea, these lenses allow the myopic wearer to focus on certain objects. These lenses are most often worn at night and removed during the day. The effect will weaken throughout the day and the lenses must be worn every night, as the effect is temporary.

Decorative Contact Lenses:Decorative contact lenses are non-corrective and are worn to alter the color or shape of the iris. Even though these contacts can be purchased without a prescription, they are still regulated by the FDA and do require a prescription.

All kinds of contact lenses carry risks and should only be prescribed by a licensed optometrist .This are all the kinds of Contact lenses and its usage are derived above for your kind info.