How Contact Lenses Have Evolved
By Michael J. Dodd, MD
Contact lenses are an option to correct optical (refractive) errors of the human eye. There are four general types of refractive errors: myopia (nearsightedness), hyperopia (farsightedness), astigmatism and presbyopia (aging eyes which requires reading glasses). Combinations of these can occur. For example, a patient may have myopia with astigmatism, or astigmatism with presbyopia.
In the 1600s glass could be ground with increasing accuracy and precision. The optical profession emerged once it was realized that certain people could see improvements in vision when looking through certain shaped lenses. Trial and error led the glass merchants to assist people with optical errors.
Over the past 300 years many obvious improvements in spectacles have been developed, but correction of refractive errors always involved placing the corrective lenses in front of the eyes. It was not until 1887 that someone developed lenses small enough to be placed on the surface of the eye (although da Vinci illustrated the concept in 1508). These early contacts were made of glass, were very large and covered part of the white of the eye and were quite uncomfortable. These were the first “hard contact lenses.”
By 1939 the first plastic hard contact lenses were developed. These were still large and uncomfortable. But cleaver scientists were able to manufacture smaller and more precise contact lenses and improve the comfort with better plastics like “polymethylmethacrylate.” These small contacts became popular in the 1950s and 1960s and for the first time, realistically allowed patients to temporarily get rid of their glasses. However, there were limitations; it took several days to build up wearing time and they could not be worn for more than about 10 hours a day.
Since then, new materials have been developed, including silicone, which makes the lenses more comfortable and allows for longer wearing times. These silicone lenses are known as “gas permeable lenses,” which means they allow oxygen in the air to penetrate the lens and assist nourishing the corneal surface cells. This extra oxygen improves comfort in addition to allowing longer use.
The next development was soft contact lenses. These are made of soft flexible polymers. These are very easy to wear in terms of comfort and are now the most popular type of contacts. However, they do require more maintenance; they must be kept in a fluid-filled container when not worn, and they must be cleaned after each use. With reduced manufacturing costs and to avoid the storage and cleaning issues, now “daily wear soft lenses” are available which can be thrown away after one day of use.
Today most patients with the four refractive errors I noted first can be fit accurately with soft contact lenses. There still are some patients today who enjoy both hard and gas permeable contacts and wear them with great success. Consult your eye physician to see if you are a candidate for contacts and be sure to follow your doctor’s instructions to avoid any complications.
Dr. Dodd is a practicing ophthalmologist at Maryland Eye Associates located in Annapolis, Prince Frederick and Upper Marlboro, as well as an instructor at the University of Maryland Department of Ophthalmology. He can be reached at 410.224.4550 or [email protected]
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