What are contact lenses?
A contact lens, or simply contact, is a thin lens placed directly on the surface of the eye. Contact lenses are considered medical devices and can be worn to correct vision, to enhance vision or for cosmetic or therapeutic reasons. In 2004, it was estimated that 125 million people (2%) use contact lenses worldwide, including 28 to 38 million in the United States. In 2010, worldwide contact lens market was estimated at $6.1 billion, while the U.S. soft lens market is estimated at $2.1 billion. Some have estimated that the global market will reach $11.7 billion by 2015. As of 2010, the average age of contact lens wearers globally was 31 years old and two thirds of wearers were female.
Why choose contact lenses?
People choose to wear contact lenses for many reasons. Aesthetics and cosmetics are often motivating factors for people who would like to avoid wearing glasses or would like to change the appearance of their eyes. Other people wear contacts for more visual reasons. When compared with spectacles, contact lenses typically provide better peripheral vision, and do not collect moisture such as rain, snow, condensation, or sweat. This makes them ideal for sports and other outdoor activities. Contact lens wearers can also wear sunglasses, goggles, or other eyewear of their choice without having to fit them with prescription lenses or worry about compatibility with glasses. Additionally, there are conditions such as keratoconus and aniseikonia that are typically corrected better by contacts than by glasses.
Types of contact lenses.
Contact lenses can be classified in many different ways. Contact lenses can be separated by their primary function, material, wear schedule (how long a lens can be worn before removing it), and replacement schedule (how long before a lens needs to be discarded). The types of corrective lenses are: Corrective contact lenses, cosmetic contact lenses, therapeutic contact lenses, rigid lenses, hybrid and soft lenses.
Contact lenses are generally safe as long as they are used correctly.Complications due to contact lens wear affect roughly 5% of contact lens wearers each year. Improper use of contact lenses may affect the eyelid, the conjunctiva, and the various layers of the cornea. Poor lens care can lead to infections by various microorganisms including bacteria, fungi, and Acanthamoeba. Many complications arise when lenses are worn differently than prescribed (improper wear schedule or lens replacement). Sleeping in lenses not designed or approved for extended wear is a common cause of complications. Many people go too long before replacing their lenses, wearing lenses designed for 1, 14, or 30 days of wear for multiple months or years. While this does save on the cost of lenses, it risks permanent damage to the eye and loss of sight.
Usage of contact lenses
Before touching the contact lens or the eye, it is important to wash hands thoroughly with soap and rinse well with water. Soaps that contain moisturizers or potential allergens should be avoided as these can cause irritation of the eye. Drying of hands using hand towels or tissues, prior to handling the lenses, can transfer lint (‘fluff’) to the users hands and, subsequently, to the lenses, causing irritation upon insertion. Hand towels, unless freshly laundered on a high temperature wash, are frequently contaminated with large quantities of bacteria and, as such, should be avoided when handling lenses. Dust, lint and other debris may collect on the outside of lens cases. Again, hand contact with this material, prior to handling the lenses, may transfer it to the lenses themselves. Rinsing the case under a source of clean running water, prior to opening it, can help alleviate this problem. Next the lenses should be removed from their case and inspected for defects (e.g. splits, folds, lint). A ‘gritty’ or rough appearance to the lens surface may indicate that a considerable quantity of proteins, lipids and debris has built up on the lens and that additional cleaning is required; this is often accompanied by unusually high irritation upon insertion.