Discover the types of contact lenses. Contact lenses have become the option of choice for most people requiring prescription lenses. Today, there are four specific types of contact lenses and three primary uses for them. The primary use of contacts is vision correction; one specialized form of correction is called Orthokeratology, or Ortho-K. This specific disease process is described in further detail with rigid lenses. The third use of a contact is for aesthetic purposesÛthese are called plano lenses, and they simply change the way the eye looks. These lenses do not alter the vision of the wearer. They merely change the physical appearance of the eye to third parties. People use these lenses to give them the appearance of having tiger eyes, cat eyes, or eyes the color of purple, red, blue, green, et cetera. In order to make an informed decision on what types of contact lenses are best suited for you, it is necessary to understand each type. This should be done in conjunction with your optometrist or ophthalmologist. The four different types of contact lenses are: rigid gas permeable (RGP), extended wear contact lenses, soft contact lenses, and disposable, or replacement schedule, contact lenses.
The rigid gas permeable contact lenses, or RGPs, are far more durable than soft lenses. This type of contact is named because, unlike its glass predecessors, it allows oxygen to permeate the lens and reach the cornea, thus the term semipermeable. RGP lenses are initially uncomfortable and can take up to several weeks for the eye to adjust to their presence. RGP lenses are known for their ability in correcting keratoconus-a structural degeneration of the cornea. Keratoconus is a disease process that changes the corneal cells into a conical shape. Patients diagnosed with keratoconus have more favorable results using RGP lenses than they do wearing regular glasses.
When considering rigid or soft lenses, it is important to decide if you want to wear them overnight or just during the day. Some contacts are specially designed so that they may be worn for one to seven days straight. These are called extended wear contacts. They are available in both soft and rigid forms. Because they are worn for extended periods of time, they have a higher risk of complication and infection. People choosing to use extended wear contacts will have to visit their prescribing doctor on a regular basis. Extended wear lenses are not capable of correcting all vision problems and are only an option for select visual impairments.
There is a subsection of extended wear lenses called extended wear disposable. These types of contact lenses are only available in soft form. At the end of one week these are simply thrown away and replaced with a new pair. Albeit they have significantly reduced risk of infection and require no cleaning, they are unable to provide the same clarity and sharpness as RGP lenses.
Like the extended wear disposables, there are daily wear disposables. They are known as disposable contact lenses or replacement schedule lenses. These are primarily soft lenses and they are prescribed according to a preset schedule. Most people that opt for disposable lenses receive their contacts each month in a bulk delivery. To be considered a true disposable, the lenses would need to be replaced every day; however, in most cases the lenses are worn for one week. They differ from extended wear because they are designed to be removed at night.
The types of contact lenses known as soft contacts are named after the flexible plastics and hydrogels used in their production. Soft lenses are made from semipermeable materials, mostly silicone, that allow for oxygen to penetrate through the lens and reach the eye. Soft contacts are favored for their comfort. Soft contacts are immediately comfortable to the wearer, but due to their thinner and more flexible construction, they tear easily and require more frequent replacement.
The Food and Drug Administration (FDA) does not list the hybrid lenses as one of the different types of contact lenses; however, the American Optometric Association considers them a stand alone variation. The reason for such discrepancy stems from the fact that they are simply a combination of RGP and soft lenses. This types of contact lenses come as either a rigid lens center with a soft lens ring, or as a small rigid lens on top of a larger soft lens-hybrid lenses are not common.