[ THE QUEST FOR OXYGEN ]
This month, Review of Optometry continues an important series of articles on the people who have made groundbreaking contributions to the contact lens field. This series represents a rare chance for us to truly make a difference. By educating ourselves about the giants on whose shoulders we stand, we make it possible to keep reaching for new heights. By understanding the scientific, social and technical challenges early contact lens pioneers faced, we can motivate and inspire ongoing technological development. And, by exploring the growth of contact lens specialty practices, we can see more clearly the foundation upon which every successful practice is built.
As the Chair of the American Optometric Associations Cornea & Contact Lens Section, I was thrilled when the editors of Review brought this project to me. I am proud to have an opportunity to play a role in documenting our collective history as optometrists and contact lens specialists. Contact lenses, the largest subspecialty in optometry, have shaped our profession. In recent years, optometrys role in therapeutic care, surgical comanagement and other specialty areas has expanded in exciting ways, but contact lenses remain at the core of the optometric practice.
We began the series last month with a look at the early pioneers who brought us the first practical contact lenses. This month, well examine developers of the modern contact lens, contact lens solutions, and our evolving understanding of the requirements of the cornea for successful lens wear. Finally, next month, well look at the people who built the first specialty contact lens practices. Well cover not only the history butequally importantwhat is happening today and tomorrow in optometry.
This is primarily a story about optometry. Although many others have made great contributions to the field, it is beyond the scope of this project to cover them all.
I hope you enjoy and learn from this salute to our profession.
Viva la Contact Lens! Jack Schaeffer, O.D.
Supported by generous grants from Alcon and CooperVision
By 1970, contact lens wear had become more practical and more comfortable than in previous decades, and as many as 2 million people worldwide were successfully wearing contact lenses.1
For the next decade, Bausch & Lombs Soflens, the first hydrogel contact lens based on Otto Wichterles lens and the spincasting process by which it was made (also acquired from Wichterle), essentially dominated the marketplace. However, corneal hypoxia or oxygen deprivation of the cornea continued to be a serious impediment to safe and successful contact lens wear, even with the new soft hydrogel lenses just entering the market. As early as 1952, Edward Goodlaw, O.D., had suggested that contact lens wear could cause corneal edema. Further research proved that to be correct. The quest to deliver more oxygen to the cornea was on.
Over the next three decades, the ranks of contact lens wearers would grow to more than 80 million, thanks in large part to the contributions of oxygen researchers in academia and clinical practice.
The Berkeley Group
From the mid-1960s through the mid-1980s, a group of researchers at the University of California at Berkeley worked tirelessly investigating the amount of oxygen needed by the cornea during contact lens wear and the effects of various types of contact lenses on oxygen transmission.
Irving Fatt, Ph.D., F.A.A.O. (19201996), and Richard M. Hill, O.D., Ph.D., F.A.A.O., worked together at Berkeley to come up with a method for measuring how much oxygen penetrates a contact lens to reach the cornea. Dr. Fatt, whose expertise was in petroleum and bioengineering, took an engineering approach to the problem, measuring oxygen flux with electrodes. He realized that the same principles of fluid dynamics applied whether one was looking at petroleum, oxygen through plastic packaging or oxygen through a hydrogel device on the eye. He introduced the concepts of material permeability (Dk) and transmissibility (Dk/L) to the contact lens industry,2 and his research resulted in a universally recognized unit for oxygen permeability (the Fatt unit) that greatly advanced the science behind both rigid gas permeable and hydrogel lenses. He also discovered that oxygen transmissibility of hydrogel lenses is proportional to polymer water content and the reciprocal of lens thickness,2 findings that were later confirmed by his colleagues.
Dr. Hill took a more physiological approach, exposing rabbit corneas to variously calibrated oxygen chambers and comparing the rates of swelling in those chambers to those of various contact lenses to determine the amount of oxygen being transmitted. This became known as the equivalent oxygen percentage (EOP) method and is still in use today.
Dr. Hill later moved to Ohio State University (OSU), where he was a researcher, faculty member and eventually dean of the school of optometry. He continued his work on contact lenses, oxygen, and on the tear film and dry eye. Dr. Hill is renowned for establishing a solid basic science foundationbut one that always had a practical bent. A superb educator, he always sought to translate his research findings in a way that would benefit clinical practice.
At OSU, Dr. Hill collaborated with William Joe Benjamin, O.D., to study oxygen transmission in human corneas. Dr. Benjamin continues to carry the oxygen mantle. As the director of clinical eye research at the University of Alabamas Vision Science Research Center, he is still exploring how Dr. Hills and Dr. Fatts oxygen measurements relate to one another.
People like to argue over which method is better, but the truth is that both are very useful and have complemented each other nicely, Dr. Benjamin said. He believes that Dr. Hills greatest legacy may be that he was able to steer optometric research out of the limited realm of physiological optics and into the physiology of the entire eye, including the ocular surface. We take it for granted now, but that was a huge jump for the field.
Drs. Fatt and Hill were not the only bright minds at Berkeley focused on the oxygen issue. Senior faculty members Robert Mandell, O.D., Ph.D., F.A.A.O., and Morton Sarver, O.D. (19221986), and two young colleagues of theirs, Kenneth Polse, O.D., M.S., F.A.A.O., and Michael G. Harris, O.D., J.D., M.S., F.A.A.O., all collaborated on measuring corneal swelling during contact lens wear, and then correlated the amount of swelling to the amount of oxygen being transmitted. Three of them (Drs. Sarver, Polse, and Harris) eventually formed a research group that examined corneal swelling related to many different contact lens designs, fits and materials.
Dr. Mandell is perhaps best known in the field for his classic textbook, Contact Lens Practice. He developed a hand-held topographer for measuring infants eyes and did a great deal of work on corneal pachometers needed for the contact lens studies he and his colleagues conducted.
Dr. Sarver had been trained as a civil engineer before he went to optometry school, and he brought an engineers meticulous attention to detail to his optometric research. He was regarded as an outstanding teacher, astute clinician, and giant in the research field. More than 1,500 Berkeley optometry students learned about contact lenses from Dr. Sarver. His faculty duties there were only at the 50% level, because he maintained an active clinical practice, but colleagues say that 50% of Dr. Sarvers time was the equivalent of 110% of a lesser mortals.
He combined the best of clinical practice and scientific research, said Dr. Harris, who says it was a tremendous honor for him as a young graduate to work alongside his former instructors, Drs. Sarver and Mandell. They fostered a friendly, nurturing environment for talented researchers at Berkeley.
Dr. Harris, who also has a law degree, has devoted himself not only to contact lens issues but to research and writing on legal issues affecting the practice of optometry. Recently retired, he remains very active in the field.
Dr. Polse established a tear mixing laboratory with an engineering colleague at Berkeley to promote safer and more comfortable contact lens wear. In his university biography, Dr. Polse notes that discovery and clinical implementation require close collaborative efforts between basic and clinical scientists. This philosophy certainly guided his own career, and he continues to work to ensure that it will continue with a program to provide grant funding for clinician scientists.
Separately and jointly, the members of the Berkeley group published hundreds of papers about oxygen, the cornea, contact lenses, and patient responses to different contact lenses. They conducted the first in vivo corneal de-swelling studies, the first contralateral contact lens experiments to show the effects of lens-induced tearing on the cornea and the first experiments on overnight wear of contact lenses. They defined the relationship between corneal edema and its clinical manifestations, and developed criteria for successful contact lens wear.
I think all of us were passionate about the art and science of contact lenses. We wanted to increase clinicians knowledge and help industry make better products for contact lens patients, said Dr. Harris.
Australia and Asia
In 1976, Brien A. Holden, Ph.D., F.A.A.O., D.Sc., O.A.M., established the Cornea and Contact Lens Research Unit (CCLRU) at the University of New South Wales in Australia. For many years, the CCLRU was one of the most highly respected and prolific research centers in optometry. Researchers there conducted some of the first studies on extended wear lenses; identified the incidence and causes of giant papillary conjunctivitis, microbial keratitis, and other complications of contact lens wear; and reported much of the early clinical findings about disposable lenses and silicone hydrogels.
The list of scientists and clinicians who have worked and studied there is a veritable whos who of optometry in the United States and abroad. Almost every standard or base of knowledge in contemporary contact lens research has its foundation in CCLRU work, said former CCLRU fellow Cristina Schnider, O.D., now an executive with Vistakon.
Prof. Holden staked his reputation on the talented people drawn to the CCLRU, supported them and promoted their careers. He has very high expectations of others, but hes also enormously supportive and kind, Schnider said.
Over the years, Prof. Holden has written or coauthored nearly 300 scientific papers, including two landmark papers with George Mertz, O.D. (19462002), that established standards for the minimum oxygen requirements to avoid corneal edema from contact lens wear.3,4 Dr. Mertz, a former petroleum engineer who received his optometry degree from Berkeley, spent a year at the CCLRU studying the ocular physiological response to extended wear of contact lenses.
He and Prof. Holden developed a micropachometer and an algorithm for measuring overnight corneal edema and then examined the relationship between overnight corneal edema and contact lens oxygen transmissibility. They determined that contact lenses needed to have an average Dk/t of at least 24.1 for daily wear and at least 87.1 for extended wear in order to keep overnight corneal swelling to 4% or less. It would be many years after this 1984 publication before the industry would be able to produce lenses that actually met the overnight wear standards.
A brilliant researcher, Dr. Mertz was known for his encyclopedic knowledge of literature and science, and for his integrity, according to Dr. Schnider. With his gruff manner, Dr. Mertz could be intimidating at first, but closer association revealed a kind and gentle soul in this big teddy bear of a man, she said. Much of his career was spent in clinical research and professional education in the contact lens industry, where he held executive management positions at Bausch and Lomb, CIBA Vision, and Vistakon.
Prof. Holden continues to be closely involved with contact lens research, but his interests in recent years have broadened to include social justice and public health. He now dedicates much of his time to global blindness prevention efforts as chair of the Refractive Error Working Group of the World Health Organization (WHO) and the Refractive Error Program Committee and board of trustees of the International Association for the Prevention of Blindness (IAPB). He is co-chair of the Vision 2020 Australia group, which strives to eliminate avoidable blindness by the year 2020. He is also executive chair of Optometry Giving Sight, which brings together all the blindness prevention NGOs, the World Council of Optometry and its member affiliates in every country, and the International Centre for Eyecare and Education to raise funds to eliminate blindness and impaired vision due to uncorrected refractive error for 300 million people in need throughout the world.
His longtime colleague at the CCLRU, Deborah Sweeney, B.Optom., Ph.D., said of Prof. Holden, Not only does he challenge his colleagues to perform at their best, but he has consistently challenged the contact lens industry to make better products. Prof. Sweeney currently serves as CEO of the Vision Cooperative Research Centre (CRC). She has authored numerous clinical papers and scientific works, including a book on silicone hydrogel lenses. She currently serves as president of the International Association of Contact Lens Educators and is a past president of the International Society for Contact Lens Research.
Another important pioneer in the quest for oxygen, Hikaru Hamano, M.D., is a legend in his home country of Japan. In the early 1970s, Dr. Hamano was the first in the world to demonstrate the partial oxygen pressure on the cornea under PMMA lenses. He conducted landmark research into how contact lens wear affects the corneal epithelium, corneal nerves and tear composition.
As the head of the largest private contact lens practice in the world, Dr. Hamano was able to perform numerous large-scale, meticulous clinical studies to validate basic findings on the importance of oxygen transmission to the cornea and examine the properties of new lenses. For example, in 1994, he conducted a study that compared complication rates of various contact lens modalities in 23,000 patients. This study did much to establish the safety of the daily disposable modality.
[ LENS MATERIAL AND DESIGN ]
[Contact Lens Care Systems]
Contact lens cleaning and care solutions are critical to the safety and comfort of lenses, but they are often given short shrift by practitioners and patients, according to Ralph P. Stone, Ph.D. Unfortunately, even clinicians dont spend enough time instructing patients on the care protocols for their lenses and cases, he said.
One of the earliest pioneers in the contact lens solution realm was Harry Hind, Ph.D., a California chemist and founder of Barnes-Hind who made the first cleaning solution for PMMA lenses. When HEMA lenses were first introduced in the early 1970s, patients had to make their own saline solution using salt tablets. The first big push into chemical disinfection came from a company called Burton Parsons, which was later acquired by Bausch & Lomb. BP licensed the technology to B&L, but the company was ultimately sold to Alcon. Around the same time, Dr. Hinds and Joseph Krezanoski, Pharm. D., were also experimenting with soft lens disinfectants.
Throughout the 1970s and early 1980s, there were numerous exciting developments in the chemistry of contact lens care, and the solutions development paralleled or even stayed slightly ahead of contact lens development. By 1980 to 1981, there were quite a few chemical disinfecting solutions on the soft lens market, sold by Burton Parsons, Allergan, Alcon, and Bausch & Lomb. These were mostly simple disinfectants, preserved with a combination of chlorhexidine and thimerosol, benzalkonium chloride (BAK) and other preservatives, and were used with hard lenses. Consumers still needed to use saline solution along with the cleaner.
The second generation of soft lens care products would encompass hydrogen peroxide cleaners such as AOSept, originally from American Optical Company and later acquired by CIBA Vision. Additionally, enzymatic cleaning products were developed to remove protein deposits on the lenses. Pioneers in this endeavor included Hemper Karagosian at Allergan and Kiran Randiri, Ph.D., at Alcon. The early peroxide systems were popular in the early 1980s with the increasing incidence of allergic reactions related to thimerosol and chlorhexidine. With patients not replacing lenses for long periods, enzyme cleaning was a necessity, although these products remained largely peripheral.
In the mid- to late 1980s, scientists introduced the next generation of disinfectants, using polyhexamethylene biguanide (PHMB) and Polyquad preservatives. These included Alcons OptiFree line and Bausch & Lombs ReNu (developed by Dr. Randiri; Lai Ogunbiyi, Pharm. D.; Frank Smith, Ph.D.; Tom Reidhammer, Ph.D.; Dr. Stone and others). These products were originally approved and marketed as disinfectants only with separate cleaners; a few years later, they would cross over into the multipurpose solution category.
By this time, earlier problems with lens-solution interactions had been resolved through an FDA-initiated lens classification system that Dr. Stone helped craft. First published in 1985, the new system classified lenses according to their polymer properties, making it easier to test new lens care products for compatibility.
In the early 1990s, Dr. Stone and Mary Mowrey-McKee, Ph.D., developed the Complete line of products for Wesley-Jessen (later marketed by Allergan and then AMO). After developing Complete, Dr. Stone went to Alcon, where he worked on novel liquid enzyme cleaners and other products, including the fourth-generation preservative Aldox, a key ingredient in the OptiFree multipurpose solutions.
Multipurpose solutions have been overwhelmingly popular for their convenience and ease of use. But, the recall of two major brands (AMOs Complete MoisturePlus and B&Ls ReNu with MoistureLoc) has reinforced the importance of the clinician in teaching lens wearers about proper care and compliance with cleaning regimens.
Another challenge for the lens care industry is the growing dominance of silicone hydrogel lenses, which so far have defied easy classification according to the system devised earlier for hydrogel lenses.
At this point, care systems may be lagging a little behind lens development, said Dr. Stone. SiHy lenses are certainly forcing us to re-think the way we look at care products.
From the quest to understand the oxygen needs of the cornea, through tremendous efforts of dozens of individuals to improve the materials, design and fitting of contact lenses, and the improvements in care systems, the contact lens field has edged ever closer to its ideal of successful, healthy contact lens wear for all who want to wear lenses. Modern contact lenses have come a long way from the days of the glass vial HEMA hydrogel lenses that dominated the market in the 1970s. Who knows what exciting innovations the future will bring. But, its a given that industry and clinicians will continue to build on the tremendous progress of the past few decades.
In tandem with the growing understanding of the importance of oxygen to the cornea, many exciting new materials have been developed since the old days of PMMA lenses, and lens manufacturers and clinicians have made numerous discoveries of the best way to design and fit contact lenses.
Lens Design Pioneers
In addition to his work on oxygen and the cornea, Dr. Mandell also worked on many contact lens design problems. He conducted studies to determine the optimal contact lens edge contour, prism effects, peripheral curve relationships, minus carrier construction and keratoconus lens design. Dr. Mandell also developed the first one-piece monocentric bifocal in 1967, and later several other bifocal lens designs. Although he retired from Berkeley in 1994, Dr. Mandell still guest lectures there and remains very active in the development of new contact lenses.
Boston optometrist Donald R. Korb, O.D., F.A.A.O., is one of the fields greatest examples of a clinician scientist. His astute clinical observations and insights have been immensely valuable to the understanding of contact lens behavior, Dr. Mertz wrote.5
In the mid-1960s, Dr. Korb described the phenomenon of central circular clouding (CCC), or edema, that occurs with PMMA lenses.6,7 He advised clinicians to rely on fluorescein staining for an accurate differential diagnosis, something that was contrary to the prevailing wisdom of the time. He also recommended fitting principles to avoid CCC. One of his early papers on CCC was co-authored with Joan Exford, O.D., a young optometrist who would later become Dr. Korbs wife and partner and with whom he would write many more important scientific papers.
Joan M. Exford Korb, O.D., F.A.A.O., went on to serve as the first female president of the American Academy of Optometry. She is a trustee of the New England College of Optometry and a member of the National Optometry Hall of Fame.
Early on, the Korbs were very interested in the interaction of the lid, cornea and tear film. In 1970, they introduced an important fitting technique, known still as the Korb fit, in which a PMMA contact lens is fit to adhere to the upper lid. Completely contradictory to common practice at the time, the Korb fit dramatically improved the exchange of oxygenated tears beneath the contact lens.8
In 1977, Dr. Korb and colleagues described a syndrome they called giant papillary conjunctivitis, or GPC.9
Don Korb has a dynamic sense of how things work, and the intellectual curiosity to look beyond the obvious, said Art Epstein, O.D.
One of the things he noticed was that contact lenses were starving the cornea of oxygen. Inspired by the rabbits third eyelid, a transparent nictitating membrane, Dr. Korb set out to make a lens that was only as thick as a few epithelial cells, or about 30m thick. That was a pretty arrogant proposition, he acknowledges now. At the time, rigid lenses were 200m to 300m thick.
Nevertheless, in 1972, he patented the CSI Lens, the first ultrathin non-HEMA soft lens. Polymer chemist Miguel Refojo and others helped create the revolutionary new membrane lens, as it was often called. It was approved by the FDA and launched by Syntex and Sola/Barnes-Hind in 1981.
In addition to his numerous contributions to lens design, materials and fitting, Dr. Korbs greatest legacy will likely be in the area of dry eye and lipid layer physiology.
He considers his best work to date to be a 1980 paper that first named meibomian gland dysfunction (MGD) and identified it as a cause of contact lens intolerance.10 This work was performed with Antonio Henriquez, M.D., Ph.D., an ophthalmologist, pathologist and corneal surgeon who was and remains very close to the Korbs. One result of malfunctioning meibomian glands is an inadequate tear film lipid layer. In the late 1980s, Dr. Korb invented Soothe, a metastable oil-in-water emulsion that has been shown to more than double the thickness of the lipid layer. It is now marketed and sold by Alimera Sciences.
Dr. Korb also recently identified a tiny and previously overlooked part of the eye, akin to a windshield wiper. The lid-wiper is the portion of the marginal conjunctiva of the upper eyelid that acts as a wiping surface to spread the tear film over the ocular surface, or the surface of contact lenses. Lid-wiper epitheliopathy (LWE), as described by Dr. Korb and colleagues in 2002 and 2005,11-12 is highly correlated with symptomatic dryness in contact lens wearers. Since it often occurs in the absence of any corneal staining that would provide clinical confirmation of dry eye, LWE may hold the key to understanding an entire segment of contact lens intolerant patients.
His dry eye research has given Dr. Korb great credibility in the medical eye-care community. I think we have to credit him with being one of the first anterior segment specialists in optometry, said Dr. Epstein. If not for the respect he almost single-handedly gained for our profession, we would be nowhere in terms of medical treatment of the eye.
Both Donald and Joan Exford Korb continue to innovate, research and see patients in the practice they founded: Korb & Associates of Boston.
The man who first introduced the Korbs to each other, Irvin M. Borish, O.D., F.A.A.O., is one of the most influential leaders in optometry. No account of pioneers in the field would be complete without him. Dr. Borish is probably best known for his classic textbook, Clinical Refraction, first published in 1944, and for expanding optometrys scope of practice by launching the movements for diagnostic and therapeutic prescribing authority in the late 1960s.
He is equally distinguished in the contact lens field. Dr. Borish was one of the first people to wear bifocal contact lenses, and he became an expert in fitting them. His many papers on contact lens patient care show his profound mastery of the subject.12 Dr. Borish was vice president of the Indiana Contact Lens Co., where he developed new techniques for improving optical characteristics of contact lenses. Along with Joe Goldberg, O.D., he founded the Association of Contact Lens Manufacturers. In lectures, Dr. Borish continues to remind his colleagues that optics and contact lens fitting remain at the core of the profession.
Rigid Gas Permeable Lenses
New York optometrist Leonard Seidner, O.D., is considered by many to be the godfather of gas permeable lenses.
An important early contact lens practitioner, Dr. Seidner was also possessed of an entrepreneurial spirit. He and his brother formed Guaranteed Contact Lens Company, a successful small manufacturer. In 1970, they launched the Polymer Optics Contact Lens Company and commissioned polymer chemist Norman Gaylord, Ph.D., to work with them on a new, more oxygen-permeable material.
At the time, Guaranteed was already making lathe-cut soft lenses. But when Dr. Seidner realized that getting a soft lens through the newly created FDA approval process would be cost-prohibitive, he focused instead on finding a better rigid lens material. He and Dr. Gaylord created the Polycon lens, made of a siloxane-methacrylate polymer that was the first material of its kind. The lens was patented under Dr. Gaylords name in 1974 and sold to Syntex Ophthalmics, which brought it to market in 1979.
Lens early recognition that PMMA lenses caused edema and the intensity of his quest to resolve that problem was a major contribution underlying later developments, said his close friend and colleague Dr. Korb.
Dr. Seidner never stopped thinking about how to improve contact lenses. Even when I went to Las Vegas on vacation, standing there in front of the Treasure Island Casino, I had an idea for how I could make a better bifocal design, he said.
In fact, another company Dr. Seidner launched, LifeStyle (now run by his son), made the first disposable bifocal lenses. A joint venture with DuPont resulted in one of the early silicone hydrogel designs, which was later sold to a major manufacturer.
Now retired from active practice, Dr. Seidner continues to work on a new contact lens that he says could take multifocal lenses from specialty to mainstream.
Shortly after the Polycon lens was introduced, two other new entrants further expanded the fledgling RGP field. Don Ratkowski, founder of Paragon Vision Sciences, developed the Paraperm series of materials, and Perry Rosenthal, M.D., introduced the first Boston RGP material. An ophthalmologist who became fascinated with contact lenses and founded a company (Polymer Technology Corporation) to make them, Dr. Rosenthal is best known for his more recent endeavors fitting therapeutic Boston Scleral Lenses for patients with keratoconus, Stevens-Johnson syndrome, and other corneal diseases at his Boston Foundation for Sight.
Ultimately, a hyper-permeable lens, Menicon Z (Menicon) was introduced with FDA approval for up to 30 days of continuous wear.
The late 1980s was a time of tremendous growth and innovation in RGP lenses. Edward S. Bennett, O.D., M.S.Ed., who had worked under Dr. Borish and Sarita Soni, O.D., as a clinical investigator for the Polycon lens, co-authored an important textbook, Rigid Gas Permeable Contact Lenses, with Robert Grohe, O.D., that was published in 1986. By 1988, Dr. Bennett was executive director of the recently founded GP Lens Institute (GPLI), a position he still holds. GPLI is the education arm of the CLMA and, as such, is the leading source for publications, symposia, advice and other educational resources related to RGP lenses.
Reverse-geometry lens designs, introduced in the late 1980s for post-RK patients, helped create a resurgence in the modality of orthokeratology. The concept of orthokeratology had been introduced decades before by George Jessen, O.D., and advanced by pioneering optometrists such as Charles May, O.D.; Stuart Grant, O.D.; and Roger Tabb, O.D., but correcting myopia in this fashion was slow and impractical.
The first modern orthokeratology design, the Contex OK lens, utilized a reverse curve, which greatly accelerated the time required to reduce a patients myopia. This was first reported by Richard Wlodyga, O.D.; the first book addressing orthokeratology followed a few years later, authored by Rodger T. Kame, O.D. (1938-2000), and Todd Winkler, O.D.
New RGP bifocal designs in the late 1980s also led to an innovation boom that continues to this day. Specifically, the introduction of the Tangent Streak segmented translating bifocal represented the first opportunity to eliminate the problem of image jump that had plagued previous GP segmented bifocals. Dr. Bennett believes the presbyopia market is one area in which GP lenses will shine in the future. If we look back historically, there were many PMMA bifocal lenses that worked really well, except that they didnt provide enough oxygen to the cornea. With modern RGP materials, were able to meet corneal oxygen needs as well as provide effective near and distance correction, he said.
Also in the 1980s, the first hybrid technology lenses were introduced, beginning with the Saturn lens. The next iteration, the Softperm lens, had a rigid, low-Dk center with a low-water content soft lens surround. Typically worn by hard-to-fit keratoconus patients, it has been plagued by insufficient oxygen transmission as well as tears at the junction of the two materials. Recently the SynergEyes A and KC lens designs, with a hyper-Dk GP center, hold promise for the successful management of patients who could not wear GP lenses otherwise.
Another major contributor to the rigid lens correction of keratoconus is Joseph Soper, who designed a number of lenses, including one that bears his name: the Soper Cone. Leonard Bronstein, O.D., also deserves credit as an innovative pioneer in PMMA and GP design, especially in the areas of bifocals and irregular corneas. The symposium that still bears his name is one of the most successful contact lens programs in the world, with the 33rd annual meeting held in January 2007.
As soft lenses got better, safer and more comfortable, patients and clinicians naturally started to think about longer wearing periods. First in Europe and later in the United States, contact lens wearers became increasingly interested in semi-permanent vision-correction lenses they could sleep in and wear continuously for long periods of time.
London optometrist John de Carle, O.D., thought increasing the water content of hydrogel lenses from the low levels (38%) in the early HEMA lenses to approximately 75% would permit such extended wear, especially if the lenses were slightly smaller in diameter than those in use at the time, which were about 14.5mm.
After obtaining a list of suitable plastics from the library, Dr. de Carle carried out experiments in the kitchen of his London flat. He once had to apologize to the neighbors for the odors issuing from his oven when one of the jam pots of plastic he was cooking exploded. He finally created a satisfactory high-water content (72%) polymer, perfilcon A, and used it to make a new lens, which he dubbed the Permalens. He made it 12.50mm in diameter. To keep a very soft lens of that size in place, it was often necessary to make the inner radius steeper than the cornea, Dr. de Carle explained. This seemed to work very well and may be why we had far less trouble than some other practitioners. Dr. de Carle sold the rights to the technology, which was eventually acquired by CooperVision.
The Permalens was introduced in the United Kingdom in 1975 and became the first extended-wear lens approved by the U.S. Food and Drug Administration in 1981, with a 30-day extended-wear indication. It helped Dr. de Carle build one of the largest extended-wear practices in the world, at a time when few people were willing to fit these lenses.
Many of his patients would wear the lenses for three months continuously, returning to his office to have their old lenses replaced with new ones. I still think we had the right idea, Dr. de Carle said. Many patients dont like to handle the lenses or touch their eyes. In my opinion, the recent movement toward daily-wear lenses is not progress at all. We should be trying to figure out how to make a lens that is safe for a minimum of three months of continuous wear.
Consumers were certainly attracted to the convenience and freedom of the Permalens and other extended-wear lenses that were introduced shortly thereafter. However, as their popularity grew, so did the reports of clinical complications. By the late 1980s, it was clear that the risk of ulcerative keratitis was much greater with extended-wear lenses than with daily wear lenses; and in 1989 the FDA recommended that continuous wearing periods be decreased from 30 days to a maximum of seven days.
Besides his work on extended-wear lenses, Dr. de Carle is also well known for his bifocal contact lens designs, including the de Carle bifocal. He first had the idea of placing the distance portion of the lens in the center, so that portion would be steeper and allow for better tear exchange. He then experimented with three- and five-zone lenses, including a design on which the Acuvue bifocal is based. Currently, he is wearing a new lens he invented with many zones and is negotiating with industry for potential acquisition of the technology.
Undoubtedly, one of the most important developments in contact lens technology in the last 50 years is the mass production of disposable contact lenses.
Michael Bay, M.D., a Danish ophthalmologist and entrepreneur, is believed to be the first to have produced a lens intended for regular disposal. His Danalens, marketed in Denmark, intrigued executives from several contact lens manufacturing companies. The material and the lenses themselves were not particularly impressive, but the manufacturing processstabilized soft molding, in which lenses could be molded in a hydrated statehad great potential.
Johnson & Johnsons Vistakon division acquired the rights to Dr. Bays technology in 1984 and paired it with etafilcon A, a material it had acquired three years earlier. Etafilcon A had been invented by Seymour Marco, O.D., a country optometrist who ran Frontier Contact Lens Co. of Florida. Dr. Marco was already making lenses from the new material, with limited success. Hank Green, then president of Vistakon, had the vision to put a considerable amount of Johnson & Johnson research muscle and money into refining both the material and the manufacturing process. Over a four-year period, through the efforts of many scientists and engineers at Vistakon, the company went from making 100,000 lenses a day to 1 million lenses a daya scale large enough to make disposability a reality.
By the time Acuvue disposable soft lenses were launched in 1987, the companys biggest challenge was probably winning over practitioners, who were reluctant to dispense lenses without verifying the clinical performance of each and every lens on the patients eye. Stanley J. Yamane, O.D., F.A.A.O., was one of those recruited to serve on a panel of experts that had early access to the new lenses. I was initially very skeptical, he said. But after three months of dispensing these lenses to my patients and seeing that the reproducibility of the lens parameters, the quality of the lenses and the vision that patients were able to enjoy was exactly as the company claimed, I became one of their strongest advocates. Dr. Yamane would later serve as Vistakons vice president of professional affairs.
Once it was proven that disposability could work, other manufacturers rapidly launched their own frequent replacement lenses in the now-familiar blister packs. The concept of disposability was taken even further with the introduction by Vistakon, in 1995, of the first single-use lenses, 1-Day Acuvue.
Silicone Hydrogel Lenses
As contact lens developers sought to make lenses that would allow more oxygen to reach the cornea, silicone seemed like a natural fit due to its high oxygen transmission and exceptional clarity. Joseph L. Breger, O.D., spent more than a decade, beginning in 1959, trying to make contact lenses from pure silicone elastomer. A 100% silicone lens, the Silsoft lens, was introduced by Dow Corning in 1981 and is still made by Bausch & Lomb for specialty cases. But, silicone would eventually be successful only in combination with a hydrogel material. Silicone is hydrophobic, making comfort and wettability in the eye a challenge. Adhesion of early silicone materials to the cornea the suction cup effectwas also a major challenge.
CIBA Vision introduced the first successful silicone hydrogel (SiHy) contact lens, the Night & Day lens, to the global market in 1998; it became available in the United States in 2001. What you need to keep a lens moving on the eye is ion permeability, or the ability for lenses to transport solubilized salt across the lens. That was a key learning, said Lynn Winterton, Ph.D., a researcher at CIBA Vision in the early days and now the companys global head of research.
Dr. Winterton and other chemists at CIBA Vision, including Tim Grant, O.D., and John McNally, O.D., worked closely with Deborah Sweeney, Ph.D.; Eric Papas, Ph.D.; Lisa Keay, Ph.D.; and others at the CCLRU in Australia to develop the Night & Day and O2Optix (AirOptix) SiHy lenses. Underlying every successful new product, Winterton says, are fundamental ocular science contributions from the giants in the field, as well as dozens of research failures that remain in obscurity but provide key knowledge.
Bausch & Lomb had been working on silicone lenses since the mid-1970s, with many lessons learned that paved the way for its 1999 introduction of the PureVision (balafilcon A) SiHy lens. The company built up a cadre of chemists to work on silicone lenses, including Kai Su, Ph.D. (who later became an executive at CIBA Vision), Jay Kunzler, Ph.D.; Yu-Chin Lai, Ph.D.; Ron Bambury, Ph.D.; and David Seele, Ph.D. The latter two would eventually invent the balafilcon formulation. Contact lens R&D Director Dominic Ruscio, Ph.D., who helped refine the original Soflens many years before, had the idea to use a plasma surface treatment to make the lens more wettable. It was the last piece of the puzzle the engineers needed.
CIBA Visions SiHy lenses also had surface modifications to make them more comfortable in the eye. Other manufacturers that came to market a bit later took different approaches. For example, Vistakons Acuvue Advance (galyfilcon A), which was introduced in 2003, has an embedded wetting agent in the lens itself.
We are already seeing the second generation of silicone hydrogel lenses, including O2Optix (lotrafilcon B, CIBA Vision), Acuvue Oasys (senofilcon A, Vistakon), and Biofinity (comfilcon A, CooperVision), with other new SiHy lenses soon to be released.
According to Health Products Research data, SiHy lenses overtook hydrogel lenses for the first time in the first quarter of 2007, with 51% of all new spherical fits and re-fits going to SiHy lenses. Toric silicone hydrogels entered the market a little later, but they have already gone from just 13% of the market in 2005 to 40% now. And the first SiHy mutlifocal lens has captured 20% of the presbyopic soft lens market in its first year.
Next month, in the final installment in this series on contact lens pioneers, Review of Optometry will look at the people who built the first contact lens practices, leaders in the contact lens field today and the rising stars who are likely to be its innovators in the years to come.
1. Sulaiman S, Back A, Sweeney DF, et al. IACLE Database 1999, IACLE Sydney, Australia.
2. Fatt I. Oxygen Transmission. In: OH Dabezies (ed), Contact Lenses-The CLAO Guide to Basic Science and Clinical Practice (2nd ed). Boston: Little, Brown, 1989:10.1.
3. Holden BA, Mertz GW, McNally JJ. Corneal swelling response to contact lenses worn under extended wear conditions. Invest Ophthalmol Vis Sci 1983;24:218-26.
4. Holden BA, Mertz GW. Critical oxygen levels to avoid corneal edema for daily and extended wear contact lenses. Invest Ophthalmol Vis Sci 1984;25:1161-7.
5. Mertz GW. Development of contact lenses. In: Hamano, H and Kaufman HE. Corneal physiology and disposable contact lenses. Boston: Butterworth-Heineman, 1997:65-99.
6. Korb DR. Corneal transparency with emphasis on the phenomenon of central circular clouding. Encycl CL Prac:IV, Append B, 1963:106-16
7. Korb DR, Exford JM. The phenomenon of central circular clouding. J Am Optom Assoc 1968;39:223-30.
8. Korb DR, Korb JE. A new concept in contact lens design-Parts I and II. J Am Optom Assoc 1970;41(12):1023-32.
9. Allansmith MR, Korb DR, Greiner JV, et al. Giant papillary conjunctivitis in contact lens wearers. Am J Ophthalmol 1977;83:697-708.
10. Korb DR, Henriquez AS. Meibomian gland dysfunction and contact lens intolerance. J Am Optom Assoc 1980;51:243-51.
11. Korb DR, Greiner JV, Herman JP, et al. Lid wiper epitheliopathy and dry-eye symptoms in contact lens wearers CLAO J 2002;28:211-6.
12. Korb DR, et al. Lid wiper epitheliopathy and dry eye symptoms. Eye & Contact Lens 2005;31(1):2-8.
13. Baldwin WR. Borish. Springfield, Mass: Bassette Company, 2006.
[ Special Thanks ]
Special thanks to contributors Robert Davis, O.D.; Art Epstein, O.D.; and Glenda Secor, O.D., for their assistance with this series.
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