A Brief History of Contact Lens Materials
BY LORETTA B. SZCZOTKA-FLYNN, OD, MS, FAAO
This issue celebrates Contact Lens Spectrum's 20th anniversary. Anniversaries are an appropriate time look back into the events that led up to where we are today. For contact lens materials, we begin in 1887, the first documented time that glass was used to make contact lenses. However, the optical principles behind contact lenses probably date back to Leonardo da Vinci and Descartes' times in the 16th and 17th centuries, respectively.
The first glass lenses were scleral devices that Muller made in 1887 as a protective shell and Fick made in 1888 for refractive correction. Feinbloom made the first hybrid lens in 1936 by creating a scleral lens with a PMMA haptic and a central glass zone covering the cornea.
Around 1940, the first solid PMMA lenses appeared and remained the primary materials until the late 1970s.
Soft Lens Innovations
Almost 60 years ago, Professor Otto Wichterle began developing the first hydrogel contact lens in Prague. Along with assistant Lim, they first synthesized HEMA and glycol diester in 1954. Their first material, the poly-hydroxy-ethylmethacrylate gel (poly-HEMA-gel), contained about 40 percent water.
Dr. Wichterle initially tried to produce these lenses by using closed polystyrene molds and polymerizing an aqueous monomer solution. This process resulted in irregular lens edges, so in 1961 he began to cast lenses in open, rotating forms. Using glass molds, a mechano set and a generator from his son's bike, he constructed a casting device on Christmas Eve 1961. Within a week he was producing usable lenses and needed a stronger generator, so he switched to using his gramophone's motor.
To maximize the equilibrium content of water in a swollen gel, Dr. Wichterle produced the first several hundred lenses from a mixture consisting of 80 percent hydroxyethyl-methacrylate (HEMA) and 20 percent diethylenglycol-methacrylate (DEGMA). However, he later began using pure HEMA.
In 1963, Dr. Wichterle met George Nissel, the most famous producer
of hard lenses and lathing instruments of the time. Nissel gave him the idea of
ing the poly-HEMA without solvent, turning it on a lathe and later swelling it with water while it maintained its optics. Wichterle quickly patented this material and technique and called it "xerogel."
The Emergence of GP Materials
In 1978, the FDA approved the first rigid gas permeable lens in the United States in cellulose acetate butyrate (CAB). Syntex introduced its Polycon lens, a silicone-acrylate material, in 1979 in a much thinner design than the first CAB lenses because of the material's improved stability.
We continue to see hybrid lenses, which now feature a GP core and a hydrophilic skirt. The SoftPerm Lens (CIBA Vision) and the SynergEyes lens series introduced in 2005 are examples of these material marriages.
Developing Silicone Hydrogel
Silicone elastomer lenses appeared in 1981 when the FDA approved the Silsoft lens (Bausch & Lomb), owned by Dow Corning at the time. However, development of the silicone elastomer lens dates back to 1956 with Becker, a Pittsburgh optician. In 1998, B&L introduced the first silicone hydrogel lens followed by CIBA in 2001.
We've come a long way just imagine what the next 20 years will bring. Happy Anniversary Contact Lens Spectrum!
Dr. Szczotka-Flynn is an associate professor at Case Western Reserve University Dept. of Ophthalmology and is director of the Contact Lens Service at University Hospitals of Cleveland.