Historical Note
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History of Vision Correction: Contact and Intraocular Lenses Contact lenses differ from spectacles or eyeglasses in that the lenses rest directly on the eye's sensitive surface rather than being perched on the nose. Leonardo da Vinci described several possible designs in 1508, and Rene Descartes suggested a design of contact lenses of his own in 1632. The first working model based on Descartes' design, built by Thomas Young in 1801, consisted of a quarter-inch long glass tube with a lens on one end, filled with water. The open side rested on the surface of the eye whose moisture was maintained by the water in the tube. In 1887 a German glassblower designed and fabricated a contact lens to protect the eye of a patient whose eyelid had been removed. It covered the entire surface of the eye and only the central (corneal) section was transparent. In the late 1880s a Swiss physician, Eugen Fick, developed glass contact lenses in collaboration with the Zeiss Optical Works in Germany. These lenses could be ground to a prescribed shape for vision correction. Fick worked both with scleral lenses, which cover the entire surface of the eye, and corneal lenses, which cover only the central portion. At approximately the same time, French optician Edouard Kalt developed glass corneal contact lenses meant to fit closely to the eye. By the 1920s, Zeiss marketed a set of trial glass contact lenses that patients could try on to find a proper fit before placing an order. Methods were also developed to make molds of patients' eyes so that lenses could be custommade. But the lenses were still too thick to be comfortable for all-day wear. In 1936, New York optometrist William Feinbloom introduced the use of plastic in the making of contact lenses. While the corneal portion of his lens was polished glass, it was surrounded and supported by a scleral portion made of opaque plastic resin. In the same year, the plastic polymethl methacrylate (PMMA, trade name Plexiglas) was invented. Since that time, almost all "hard" (inflexible) contact lenses have been plastic rather than glass. Plexiglas lenses were found to retain their optical quality over time, and they were not prone to dangerous bacterial growth. But because the polymer is impermeable to oxygen and CO2, many wearers experienced varying degrees of eye irritation and the lenses could not be used for overnight wear. The more comfortable "soft" lenses were introduced in the early 1970s. They were invented by Czech chemist Otto Wichterle,
MRS BULLETIN/AUGUST 1997
who developed the water-absorbent polymer hydroxyethylmethacrylate (HEMA). While soft lenses provided improved gas permeability and increased ease of wear, a variety of materials-related problems remained to be solved. The polymer was susceptible to colonization by bacteria and a regime of daily disinfection was required, but even so, infection rates were high. Furthermore, the lenses were easily torn if mishandled and yellowed with age, requiring replacement every year or two. By the mid-1970s, asymmetric "toric" soft lenses
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