contact
lens materials
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.
Rigid Beginnings
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
produc-
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.
Bright Future
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.
Contact Lens Spectrum, Issue: June 2006