Cornea 19(5): 730–740, 2000. © 2000 Lippincott Williams & Wilkins, Inc., Philadelphia Twenty-five Years of Contact Lenses The Impact on the Cornea and Ophthalmic Practice Timothy T. McMahon, O.D., and Karla Zadnik, O.D., Ph.D. Purpose. The history of contact lenses has occurred in the latter treatment of ocular disease. Developments in the contact lens field half of the 20th century. In particular, events in the 1970s through have affected health care practitioners within the eye care domain the 1980s related to the invention of soft, hydrogel contact lenses and throughout medicine and dentistry in ways that have signifi- have revolutionized the contact lens industry and the eye care cantly changed the doctor–patient relationship. attached to it. This article recounts that history from the perspec- Understanding the historical importance of the pioneers who tive of market forces, inventions, and discoveries about the physi- developed the concept of the contact lens and the materials used ologic functioning of the cornea. Methods. The relevant literature is critically reviewed. Results. Discoveries about the oxygen needs provides a cornerstone for fully comprehending the impact of a of the cornea and consumer pressure for clear, comfortable, little piece of plastic placed on a cornea. Additionally, we look at around-the-clock vision have resulted in a history of rigid gas the knowledge gained in our understanding of corneal physiology, permeable and soft lenses that leads to today’s contact lens picture. contact lens-associated corneal pathology, new roles for contact The short-term and long-term effects of chronic hypoxia and the lenses in the treatment and management of corneal disease, and levels of lens oxygen transmissiblity necessary to avoid them have finally the impact of contact lenses on the doctor–patient relation- been well-described. The advent of the soft lens, followed by the ship. “human experiment” with initial extended-wear modalities, led to the advent of the disposable soft contact lens. Conclusions. In the past 25 years, the development and wide acceptance of soft contact LENS MATERIALS lenses have revolutionized the management of refractive error and corneal diseases. Key Words: Contact lens—Hydrogel—Rigid gas permeable The Soft Lens: The Otto Wichterle and Drahoslav lens—Extended-wear—Daily-wear. Lim Story Behind the iron curtain in Prague, Czechoslovakia, a chemist and director of the Institute for Macromolecular Chemistry at the Czechoslovak Academy of Sciences was busy developing a poly- In 1975, 25 years ago, the contact lens world was in the midst mer that could be used to construct artificial blood vessels and of a huge revolution that would change the face of eye care in orbital implants. Professor Otto Wichterle (Fig. 1.) and his assis- America and much of the rest of the world. Most polymethylmeth- tant Drahoslav Lim thought their new polymer hydroxyethylmeth- acrylate (PMMA) lenses were produced individually by small in- acrylate (HEMA) could be used to make contact lenses.4 This was dependently owned contact lens manufacturers for doctor clients; in the mid-1950s. An enterprising attorney named Martin Pollak, a the “soft lens” was beginning to make a noticeable penetration into major participant in a patent licensing and technology transfer American and British marketplaces, leading the charge for large company (National Patent Development Corporation in New York, manufacturers to dominate the field.1–3 Sparked by this change in NY, U.S.A.) was conducting business in Moscow and learned of a contact lens materials, ophthalmic practice has never been the new contact lens being developed in Prague. He traveled from same. This review chronicles the past 25 years of contact lenses in Moscow to Prague, happened upon Professor Wichterle, and be- ophthalmic practice and concentrates on the changes that new lens came enthralled with potential prospects for the new material. materials and care systems have had on patients, their corneas, and Knowing nothing about contact lenses, Mr. Pollak was informed ophthalmic practice. The impact of these developments is greater that the principal advantage of this new material was that fewer than one would initially believe, resulting in new knowledge of parameters were needed to fit a lens to the human cornea and that corneal physiology and a much greater appreciation for the patho- practitioners would be able to stock lenses and dispense them logic consequences of tampering with the normal human cornea. directly from their office. Pollak returned to the United States and As well, contact lenses are routinely used in the management and recruited Robert Morrison, O.D., and eventually Allan Isen, O.D., to advise Wichterle on lens design issues and production issues. It Submitted February 8, 2000. Revision received March 21, 2000. Ac- was Professor Wichterle who developed the spincasting method cepted March 27, 2000. for producing lenses from the gel polymer, initially constructing a From the Department of Ophthalmology and Visual Sciences (T.T.M.), prototype machine using his son’s erector set in his kitchen.5 Rec- University of Illinois at Chicago, Chicago, Illinois; and the College of ognizing the need for serious financial backing, Pollak entered into Optometry (K.Z.), The Ohio State University, Columbus, Ohio, U.S.A. Address correspondence and reprint requests to Dr. Timothy McMahon, a licensing agreement between Wichterle, National Patent Devel- University of Illinois at Chicago, M/C 648, 1855 West Taylor Street, opment Corporation, and Bausch & Lomb, Inc. ([B&L], Roches- Chicago, IL 60612, U.S.A. ter, NY, U.S.A.), giving much of the worldwide rights to B&L for 730 TWENTY-FIVE YEARS OF CONTACT LENSES 731 of 1998, according to the International Association of Contact Lens Educators (personal communication, Sweeney D. Interna- tional Association of Contact Lens Educators, 1999). Estimates by region indicate that 17 million people wear contact lenses in Asia, 17 million in Europe, 0.5 million in Australia, and 32 million in the United States (personal communication, Sweeney D. International Association of Contact Lens Educators, 1999). Extended-wear Contact Lenses HEMA-based hydrogels have always offered a certain degree of gas permeability. Refinements in the polymer formulations, in- cluding adding methacrylic acid, had the effect of elevating the water content of the lens polymer. Oxygen permeability is directly related (positively correlated) to the water content of the polymer and is inversely proportional to the thickness of the material. Thus, lens manufacturers were constrained by the boundaries of a very thin lens or a lens reaching such a high water content as to become dimensionally unstable, like a bag of water. Within these confines, sufficient oxygen permeability was achieved so that the FDA ap- proved the first hydrogel extended-wear lens in 1979 for aphakia for the Permalens by Cooper Vision (Fairport, NY, U.S.A.) and the Hydrocurve lens from Continuous Curve Contact Lens Company (now Wesley-Jesson, DesPlaines, IL, U.S.A.).5,6 The initial ap- proval for 14 days of extended-wear rapidly decreased to 6 nights of continuous wear due to the appearance of complications not found during the FDA approval process.8–12 The extended-wear lens was initially targeted to the aphakic patient who frequently was elderly and had difficulty with aphakic spectacles or with the insertion and removal of a contact lens. For many patients, the treatment plan was for a monthly visit to the doctor’s office for FIG. 1. Professor Otto Wicheterle. (Figure courtesy of Professor Jan Rocek.) cleaning and disinfection of the lenses. Myopic extended-wear was approved shortly after the aphakic lens approval in 1981, (the the polymer and the manufacturing rights. B&L was prepared to Hydrocurve and the Permalens) permitting myopic patients their bring their new lens to market in 1968 when the Food and Drug first real opportunity to see well at all times. This was and is an Administration (FDA) stepped in after many complaints from extremely powerful elixir to the myope (and the older hyperope) as small, family owned, contact lens laboratories and indicated that can be demonstrated by witnessing the explosion of refractive this new lens was a “drug” and would have to go through the surgery procedures performed today. standard drug approval process.6 B&L eventually received mar- Recognition that extended-wear of hydrogel lenses carried an keting approval from the FDA in 1971 for the Soflens. By 1973, increased risk for serious complications, in part, led to a dramatic 8–11 the Griffin lens (Softcon, American Optical, Inc., now Ciba Vision shift in the soft lens market. The prevailing clinical opinion of Care, Inc., Duluth, GA, U.S.A.) was approved for daily-wear. The the 1980s was that lens handling played a substantial role in the daily-wear soft lens was on its way to becoming the dominant risk of microbial keratitis. In part, this general opinion led to the product in the contact lens market. Within the next 10 years, ad- introduction of the disposable soft lens in 1987 by Vistakon (Jack- ditional polymers and a change in the exclusive distribution rights sonville, FL, U.S.A.). The Acuvue disposable lens was initially was subsequently converted to a nonexclusive license through liti- introduced as a 2-week extended-wear lens to be worn and then gation that opened the floodgates to competitors in the soft lens thrown away. Initial claims were that this lens would be safer business. because lens handling was reduced to a minimum and the lens was replaced before potentially harmful contaminants could adhere to Demographics the lens. Although disposing of the lens on a regular basis did little Today there are >25 hydrogel polymers on the U.S. market to reduce the risk of serious complications, it did reduce the ma- alone and scores of contact lens manufacturers with revenues in jority of “nuisance” complications and resulted in longer lasting the hundreds of millions of dollars supplying millions of U.S.