Contact lenses were first recognized in 1945 by the American Optometric Association. Over 38 million people wear contacts in the United States alone with international numbers topping 125 million. As more and more people receive proper eye care, the use of contact lenses continues to grow.
Leonardo da Vinci is often credited with the first conceptual model of what is now the contact lens. The rest, as they say, is (very dull) history. Other contributors to the modern contact lens include Young, Mueller, Fick, and Fienbloom, which sounds like a very overpriced law firm.
What types of contact lenses are there?
Recent innovations have led to advancements in the technology behind lenses as well as the options available. The choices are vast and with increased comfort and ease of use. When it comes to the fundamentals, there are many options available. Lenses can be hard, soft, or somewhere in between. There are further choices relating to how long lenses can be worn, the material used in production and how many uses lenses have. Different options are suitable for different lifestyles, but an ophthalmologist or optometrist can help you make sure you choose the lenses best for your personal situation. There are more factors to consider than simply which style you prefer, so be sure to trust an eye care professional’s recommendations.
Disposable soft lenses
In 1960, experiments to make contacts out of water-absorbing (hydrophilic) plastic began, and the first soft lens made of such material became available commercially in the U.S. in 1971. The water content of today’s soft lenses ranges from just under 40 percent up to about 80 percent. They normally cover all of the cornea and part of the sclera (white of the eye).
Most disposable soft contacts are designed to be worn from one day to one month, depending on the lens material. They often have high water content and are usually made with thinner, more flexible materials. One-day contacts are disposed of after each use but longer term disposable contacts must be cleaned and disinfected after each removal. Disposable contacts can be prescribed for daily use or extended wear, depending on the brand and purpose in question.
Disposable daily wear lenses first became available in 1987 and exploded in popularity soon after in the 1990s. Daily wear two-day lenses were introduced in 1991, followed by tinted disposable lenses in 1992, one-day disposable lenses in 1995 and multifocal disposable lenses in 1998.
Disposable contacts do not last forever. Each brand of contact lens has a specifically recommended replacement schedule based on the ability of the lens to transmit oxygen and to shed proteins from the surface. Most contact lenses sold in the US today are either daily disposable, 2 week disposable or monthly disposable lenses.
Daily wear contacts
Daily wear contacts are intended to be worn for an entire day, generally around eighteen hours, and are designed to be comfortable for hours on end. Daily wear contacts can be reusable or disposable, meaning they are discarded after several uses.
Extended wear contacts
Daily wear contacts must be removed before sleeping but extended wear contacts can be comfortably worn both night and day.
Part of the struggle in initial extended wear contacts involved the lack of oxygen flow and the discomfort that can come from long term wear, including dry, itchy eyes. Modern technologies have made the adjustment easier with more breathable plastics and technology permitting lenses to move on the eye to prevent dirt and debris from becoming trapped under the lens.
Extended wear contacts might be convenient but there may be some health risks involved. A research study published by the American Academy of Ophthalmology in September of 1997 concluded that individuals who wear extended wear contacts are ten to fifteen times more likely to contract ulcerative keratitis than those who don’t (Preferred Practice Patterns, “Refractive Errors”).
Spherical contacts are simple spherical lenses used to treat myopia, hyperopia and presbyopia.
Toric lenses are cylindrical lenses that rely on gravity and lid interaction to rotate to the right angle in order to correct the warp in the cornea that causes astigmatism.
Multifocal / bifocal
Bifocal and multifocal contacts are intended for individuals with presbyopia. These lenses can provide two or more corrections that gradually shift throughout the contact to provide corrective refraction for aging eyes, both alone and in conjunction with additional disorders.
Monovision contacts are prescribed so that one eye is set to see far away, and the other is set to see close up and is used in patients with presbyopia. In time, the eyes and brain adjust to provide one clear field of vision. Because brains are smart.
Conventional contacts are generally worn from six months to a year, and are not frequently prescribed due to the improvements in disposable lenses. They are produced in daily wear and extended wear models and can be soft lenses, hard lenses or rigid gas permeable lenses.
Rigid gas permeable (RGP) lenses
The first RGP lenses were introduced commercially in 1979. Also called oxygen permeable lenses, RGP contacts are made of a variety of silicone-acrylate combinations. They normally cover about two-thirds of the cornea. Some contacts use a combination of soft and RGP materials to accommodate unique fitting cases. For example, there’s a lens made with an RGP center surrounded by a soft periphery.
The first lenses to hit the market in 1945 were what are now known as hard lenses. Until 1945, these lenses were made from hard glass before Plexiglass was discovered. This material is now better known as Plexiglass. Hard lenses are still manufactured in this manner due to history and quality but their use has tapered off significantly, largely due to the discomfort and lack of oxygen flow to the eye.
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Color variation in contact lenses
Due to their rarity and recessive genetic nature, pale eyes have long been desirable. Until the introduction of colored contacts, there was no way for those born with dark eyes to mimic the appearance of blue or green eyes. Highly popular in actors and actresses, many people now make use of colored contacts, whether necessary for correcting refractory errors or not.
Like any other kind of contact lens, colored lenses must be fit and prescribed by a doctor.
Opaque contacts are painted with a solid layer of color around the iris and a clear center. They are designed to change the color of even dark eyes. The natural appearance of the eye does not show through, allowing opaque lenses to completely mask the underlying color.
Enhancers, also known as medium tints, are intended to enhance or alter but not obscure one’s natural eye color. Enhancers are designed to be worn by individuals with pale eyes and will have no effects on dark eyes.
Visibility tinted lenses
Visibility tinted lenses have a very slight colored tint, generally blue, added to the lens. Unlike opaque lenses and enhancers, they will not change or mask the color of the eye in any way. Instead, the tints are used to help make a lens more visible in a lens case or should one fall out or drop. Visibility lenses are also called VISITINT or LiteTint.