Types of Contact Lenses:

Modern contact lenses fall into two categories: soft lenses that are made from water-containing plastics, and GP or "oxygen permeable" rigid contact lenses.

Contact lenses may also be classified by wearing schedule.  Daily wear lenses must be removed, cleaned and stored each night, while extended wear contact lenses are made from materials which are safe for sleep.  You may also have heard of "continuous wear" contact lenses, a type of extended wear that can be worn for up to 30 days.

Various lens designs are available for different vision problems.  Spherical contact lenses correct nearsightedness or farsightedness and are indicated by a minus or plus in your prescription, respectively.  Bifocal contact lenses are similar to multifocal eyeglasses in that they use different optical zones to correct presbyopia (the decreased ability to see at both near and far distances). Toric contact lenses correct astigmatism, which can accompany either nearsightedness or farsightedness.

Bifocal Contact Lenses provide clear vision and varying distances
Colored Contact Lenses give your eyes a subtle or dramatic change
Disposable Contact Lenses enable a healthier wearing experience
Extended Wear Contact Lenses for safe overnight wear or naps
Gas Permeable (GP) Contact Lenses for the ultimate in crisp vision
Silicone Hydrogel Contacts transmit more oxygen to your eyes
Toric Contact Lenses provide good vision if you have astigmatism

Bifocal contact lenses are designed to provide good vision to people who have a condition called presbyopia.

The main sign that you're developing presbyopia is that you need to hold menus, newspapers and other reading material farther from your eyes in order to see it clearly.

Bifocal contact lenses come in both soft materials and rigid gas permeable (GP) materials. Some can be worn on a disposable basis. That means you have the convenience of throwing the lenses out at specified intervals (even daily, in some cases) and replacing them with fresh, new lenses.

Colored contact lenses come in three kinds: visibility tints, enhancement tints, and opaque color tints.

Many of these colored contact lenses are available in plano form, as well as in designs for people who have astigmatism, need bifocals, or want a disposable contact lens.

A visibility tint is usually a light blue or green tint added to a lens, just to help you see it better during insertion and removal, or if you drop it. Since it's a very light tint, it does not affect your eye color.

An enhancement tint is a solid but translucent (see-through) tint that is a little darker than a visibility tint. An enhancement tint does change your eye color. As the name implies, it's meant to enhance the existing color of your eyes. These types of tints are usually best for people who have light colored eyes and want to make their eye color more intense.

Color tints are deeper, opaque tints that can change your eye color completely. Usually they are made of patterns of solid colors. If you have dark eyes, you'll need this type of color contact lens to change your eye color. Color contacts come in a wide variety of colors, including hazel, green, blue, violet, amethyst and gray.

The companies that make colored contact lenses have gone all out to mimic the natural look of the colored portion of the eye. Since this area is made up of colorful shapes and lines, some color contacts feature a series of tiny colored dots on the lens to make them look more natural on the eye.

But the center of the lens, the part that lies over your pupil, is clear so you can see.

Costume or theatrical contact lenses also fall into the category of opaque color tints. Long used in the movies (one example is The Man Who Fell to Earth), these special-effect contact lenses are now widely available for novelty use and can temporarily transform the wearer into an alien or jaguar, among others.

Disposable contacts are worn for a specific period of time, then thrown out and replaced with fresh lenses. Disposables have become the most common type of contact lenses.

Many eye care practitioners and consumers prefer disposable contacts for their health and convenience benefits.

What Are Disposable Contact Lenses?

You need to understand the terminology:

The term "disposable" often refers to both disposable and frequent replacement lenses.

Replacement Schedule vs. Wearing Schedule

A common source of confusion about contact lenses involves replacement and removal intervals:

• Replacement schedule refers to how often your lenses are discarded and replaced — that is, whether they are disposable, frequent replacement or reusable.
• Wearing schedule refers to how often you remove your contacts (but don't necessarily discard and replace them). Daily wear means you remove them each night. Extended wear means you sleep in them.

Disposable contacts can be prescribed either for daily wear or extended wear, depending on your eye physiology and needs.

Extended wear contact lenses may be the right option for you if you would like to wake up each day with clear vision.

Contact lenses are available for two different wear schedules:

• daily wear (you remove them before sleeping)
• extended wear (you leave them in overnight)

In the United States, the FDA has approved some contact lenses for daily wear only and others for extended wear. Extended wear lenses allow more oxygen to reach your cornea.

Most extended wear lenses are FDA approved to be worn without removal for up to seven days. A newer type of soft contact lens material, silicone hydrogel, is considered "super-permeable," and some lenses made from this material are approved for up to 30 days of wear without removal.

Also, some gas permeable lenses can be worn for up to a month at a time. This 30-day type of extended wear lens sometimes is called "continuous wear."

After recent improvements in design and materials, these lenses now can be worn safely for the full 30 days for those who can tolerate them. Even if you don't feel comfortable wearing the lenses for the full time period, you still can change them out at extended wear intervals that best suit you.

Soft contact lenses are most common, but there is another lesser-known category of contact lens materials: gas permeable (GP) contact lenses, also known as RGPs, rigid gas permeable, or oxygen permeable lenses.

GP contact lenses are rigid, but they shouldn't be confused with old-style "hard" contact lenses, which are now obsolete. Hard contact lenses were made of a material known as PMMA. Before 1971, when soft contact lenses were introduced, just about all contact lenses were made from PMMA.

The problem with PMMA lenses is that they are difficult to get used to and somewhat uncomfortable to wear. Also, PMMA does not allow oxygen to pass through it, and healthy eyes need plenty of oxygen.

A new generation of "super-permeable" contact lenses can transmit unprecedented amounts of oxygen to your cornea and, in some cases, enable 30 consecutive days of wear without removal.

Silicone hydrogel contact lenses represent a breakthrough over traditional hydrogel soft contact lenses, because silicone lets so much oxygen (essential for a healthy cornea) pass through the lens. "We're talking about lenses that breathe six to seven times more oxygen than previous lenses," says P. Douglas Becherer, OD, former chairman of the American Optometric Association's Contact Lens and Cornea Section.

Silicone hydrogel contact lenses have caught on with both wearers and eye care practitioners. By 2009, silicone hydrogel lenses are expected to account for 60 percent of U.S. soft contact lens sales (in dollars), according to equity research firm Robert W. Baird & Co.

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

Toric lenses have two powers in them, created with curvatures at different angles (one for astigmatism, the other for either myopia or hyperopia). There's also a mechanism to keep the contact lens relatively stable on the eye when you blink or look around. To provide crisp vision, toric contact lenses cannot rotate on your eye.

Toric Contact Lens Cost