According to recent statistics, 138 million people in the United States use some kind of corrective eyewear. From designer glasses to contact lenses in a variety of materials, oxygen permeabilities and tints, the range of vision correction options available today is overwhelming. To truly appreciate the technological advancement that today's contact lenses represent, we must trace the development of lenses through time -- from the first magnifying glass to the most sophisticated contact lens.
The first evidence of lens use dates back to the city of Nineveh, which existed nearly ten thousand years ago, about 200 miles north of Baghdad on the Tigris River. Discovered in the ruins of this ancient city was a piece of convex glass -- capable of magnifying objects. Archaeologists believe that this primitive magnifying glass, or "burning glass," as it was often called, was used to concentrate the sun's rays to start fires.
Another early use of lenses was to observe the stars, as mentioned in the writings of a Chinese emperor who lived in 2283 B.C. Later, in the fifth century B.C., during the time of Confucius, lenses are believed to have been used as sunglasses, but there is no evidence that they were used for vision correction.
One of the first recorded uses of lenses specifically for vision improvement was in the thirteenth century when Marco Polo observed elderly Chinese using convex lenses to help them read. At about the same time in Venice, convex lenses were mounted on a frame to form the first pair of spectacles. Originally scarce and expensive, convex lenses became more widely used as reading glasses after the invention of printing in the fifteenth century.
These early convex lenses were made of transparent quartz and beryl, and helped with farsightedness. The first evidence of concave lenses for nearsightedness dates back to the sixteenth century when a portrait of Pope Leo X by Italian painter Raphael shows the Pope holding a concave lens.
Other early achievements of note included the invention of bifocals by Benjamin Franklin in 1775 and the first use of trifocals in 1826. With the mechanization of the nineteenth century and the Industrial Revolution, enormous advances in corrective lenses were made by grinding them by machine and improving the quality of glass, making spectacles more affordable and widely available.
By the turn of last century, eyeglasses were widely available in a number of styles and powers. In addition to correcting focusing problems -- such as nearsightedness and farsightedness -- eyeglasses can prevent headaches and muscle fatigue that result from straining to see without vision correction.
The concept of corrective lens that could be worn directly on the eye was first recorded by Renaissance genius Leonardo da Vinci at the beginning of the sixteenth century, and then by philosopher and mathematician Rene Descartes in the seventeenth century. It was not until 1823 that this concept was explored further when an English astronomer announced his belief that vision could be corrected by placing a lens directly on the cornea. His theory, involved making a mold of the cornea, proved to be unfeasible since there was no effective local anesthetic to desensitize the tremendously sensitive cornea.
The next development occurred when a German glassblower created a glass disc for someone with a diseased eyelid. The disc, acting like a clear bandage, prevented the lid from touching the eyeball. Soon after that, in 1887, the first corrective contact lenses were made and tested by a Swiss physician. These initial contact lenses were made of glass and covered the entire eye surface.
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| However appealing the concept of contact lenses, the fitting process was crude and extensive. A trial set contained up to a thousand lenses, and one glass lens after another was inserted onto the eye until one was determined to be suitable. Because the lenses covered both the cornea and sclera (white of the eye), they were large and heavy, making it very difficult to center them properly.
In the 1930's American optometrist Dr. William Feinbloom created the first hard plastic contact lenses. These were fitted by taking impressions of the eye using a soft, wax like substance which subsequently hardened. Although lightweight and unbreakable, these lenses still covered the entire front portion of the eye. Hard lenses covering only the cornea weren't introduced until the 1950's. These were the first contact lenses that were widely available -- which meant that for the first time ever, vision correction did not necessarily require eyeglasses.
Soft contact lenses were introduced in 1971 for daily wear. This popularity is largely attributed to the lenses being extremely comfortable. The birth of soft lenses was inspired by Otto Wichterle, a Czechoslovakian chemist who began experimenting with a different kind of plastic called HEMA (hydroxyethylmethylmethacrylate), which is optically clear and is used in surgery because of its compatibility with human tissue.
Rigid gas permeable lenses (RGP) were introduced in 1979 and are designed to combine the visual sharpness of hard lenses with the comfort of soft lenses. RGP's are made of a flexible plastic material that allows more oxygen to reach the cornea than do hard lenses.
The world's first disposable contact lens was introduced in 1987. Disposable lenses are worn up to 30 days and then discarded and replaced with a new sterile pair. They share the benefits of comfort and convenience with conventional soft lenses, while eliminating the need for lens cleaning.
In 1994 the first daily-disposable contact lenses were introduced. These lenses are intended to be worn for a single day, then discarded and replaced with a fresh, sterile pair. Daily-disposables offers the shortest lens wear regimen possible, and eliminates the inconvenience of lens care altogether for daily wear patients.
Some of the latest options for vision correction are surgical procedures which use diamond-tipped blades or cool beams of laser energy to correct the shape of the cornea and restore vision to normal or close to normal. Radial Keratotomy (RK), Photorefractive Keratectomy (PRK), and LASIK are refractive surgical procedures that are currently used. On the near horizon are INTACS. These are plastic rings that are surgically inserted into the cornea and correct nearsightedness. Also Implantable contact lenses are being developed which are inserted directly into the eye. Some researchers are speculating that in the future vision correction may eventually be as simple as placing drops in the eyes to form instant contact lenses. A special drop, with the patient's prescription, would be placed onto the eye, and then harden immediately into a contact lens offering excellent comfort, fit and vision.
Since the development of the first convex magnifying glass used to start fires in the ancient city of Nineveh, the advancement of lens use and vision correction have made astronomical strides. Today, an overwhelming number of vision correction options are available, from eyeglasses to the most advanced vision surgery.
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