History of the PMMA Intraocular Lens

The Earliest IOLs

The history of PMMA intraocular lenses (IOLs) began with Harold Ridley in mid-twentieth century Britain. However, the idea of the IOL is considerably older and dates back to the beginning of modern cataract surgery.

The earliest references to IOLs are found in the Memoirs of Casanova. Casanova, during a sojourn in prison, had met an “itinerant oculist” named Tadini who carried with him a set of small glass lenses, intended to be placed in the eye following cataract removal. This was hardly more than a decade after Daviel’s first report on extracapsular surgery in 1753, which begins the modern era. It is uncertain if Tadini ever implanted any lenses, but a man named Casaamata, the court ophthalmologist at Dresden, who may have learned of the idea through Casanova, actually attempted the procedure in 1795. Unfortunately, his glass lens immediately sank toward the retina, ending the first chapter in the history of IOLs.¹

Between Casaamata and Ridley, references to the idea of the IOL in ophthalmic literature are rare. As for attempts to reduce the idea to practice, there has been mention of limited animal experiments using both quartz and plastic material performed in the 1940s, but nothing had come of these efforts.²

The limitations of aphakia were widely understood. These limitations included 30% magnification, loss of side vision, the “jack-in-the-box” phenomenon, distortion, and the need for thick and heavy glasses. The visual distortion could be crippling in nature, often leading to serious accidents. However, aphakia was accepted as an unavoidable consequence of cataract surgery.

A prominent, mid-twentieth century American ophthalmologist, A.C. Woods, himself aphakic, wrote that “this condition (aphakia) cannot be cured; it must be endured.”³ This was the accepted wisdom before Ridley’s revolutionary invention.

The Birth of the PMMA lens

During the Second World War, Ridley had the opportunity to examine RAF pilots who suffered injuries from shattered Plexiglas canopies and had fragments imbedded in their eyes. Ridley had observed little or no reaction in cases in which the material had come from Spitfire planes. The material involved was identified as monomer-free PMMA.

After the war, Ridley, working with Rayners Limited, had lenses ground from this material designed for implantation in the eye during cataract surgery. Ridley was convinced that the artificial lens should be placed in the posterior chamber “where nature intended the crystalline to be.” ⁴ He designed a disc-shaped lens, much like the natural lens, with a small peripheral flange that allowed him to hold the lens with forceps. The lens weighed slightly more than 100 mg in air and was approximately 8.35 mm in diameter. It was made entirely of PMMA.

It is reported that in several cases he attempted to implant the lens following intracapsular surgery using the vitreous base for support.^4,5 Intracapsular surgery had triumphed over extracapsular surgery by mid-century because it dealt more satisfactorily with the immature cataract, thereby widely extending the range of cases that could be treated. It also eliminated the problem of after-cataract. The artificial lens invariably dislocated in these cases and Ridley turned to extracapsular extraction as his preferred method.

The first successful IOL implantation was performed on November 29, 1949 at St. Thomas Hospital in London. However, excessive myopia and/or lack of adequate fixation was reported to have led to an IOL exchange in February 1950.

The clinical results of the Ridley posterior chamber lens are shrouded in time. It is reported that approximately 1,000 Ridley lenses were implanted over a decade, most of them by Ridley himself.^2,6

Complications were common and failure rates of more than 50% were often contemporaneously quoted. In hindsight, the reason for high failure rates is most likely because ophthalmic microscopes were not yet in use. Cortical cleanup techniques were primitive by current standards and were often done blindly. Sterilizing solutions then in use are now known to have caused severe reactions.

Ridley’s artificial lens was heavy and not secured inside the posterior chamber at the time of surgery. Fixation was dependent upon the formation of adhesions between the iris and the capsule. Surgical success required a sufficient inflammatory reaction to encapsulate the artificial lens, and yet not so much so as to cause irreversible damage.

Despite the high complication and failure rates, Ridley had demonstrated that pseudophakia was feasible. A significant number of patients who received the Ridley IOL in the early days of implantation achieved good visual results. Some of these patients were still being followed many years later in both America and Europe.

Revolutionary concepts are rarely welcomed in medical endeavor. Moreover, the promise of pseudophakia had been masked by complications. The professional reaction was one of open hostility. Almost all the leading voices in ophthalmology were united in opposition to the procedure. Ridley was vilified. His lens fell into disrepute and the procedure was abandoned. Fortunately, Ridley would live long enough to see the greatness of his achievement recognized. In February 2000, approximately 50 years after his first effort, Queen Elizabeth knighted him for his contribution.

Following in Ridley’s Footsteps

Despite the perceived failure of Ridley’s posterior chamber lens, he had raised awareness of new possibilities for patients with cataracts. Attention turned to the possibility of anterior chamber implantation. Implantation in the anterior chamber was technically easier and was compatible with intracapsular surgery. Also, fixation could be achieved at the time of implantation by adding haptic struts to the lens that could be wedged into the angle. The first anterior chamber lens was implanted by N. Baron in 1952. The prototype for most anterior chamber lenses is frequently said to be that of Benedetto Strampelli, who actually reported earlier than Baron, especially as modified by Peter Choyce.⁶

Ridley, after abandoning his posterior chamber lens, designed a tripodial anterior chamber lens with footplates at the tips of the tripod for seating in the angle.

Different surgeons suggested multiple variations of the angle-supported lens. Dannheim was the first to use closed loop supports made of flexible suture-like material for implantation in the anterior chamber. Unfortunately, many of these early anterior chamber lenses were ill conceived or poorly manufactured. The edges were sharp, the haptics were thick, and the suture material used for closed loops sometimes became reabsorbed in the angle. Delicate angle structures frequently failed to withstand the mechanical pressure applied by the lens. What initially appeared to be success, often evolved into failure.

Alternatives to angle support were suggested by Epstein in 1953 with the collar stud, and later, the Maltese Cross design, and the iris clip lens by Binkhorst in 1957. These lenses were centered on the pupil with supports extending both in front of and behind the iris. The haptic supports terminated short of the peripheral iris, so theoretically the only tissue these lenses would contact was the iris.

Joaquin Barraquer most likely performed the largest series of anterior chamber implants during the 1950s at the Baroque Institute in Barcelona, Spain. Barraquer implanted several hundred anterior chamber lenses. Most were of the closed loop variety. Some of these lenses were implanted in phakic patients who were severely myopic. Toward the end of his series, he began cutting open the loops of the lens, hoping to decrease the tendency of his anterior chamber lens to bow forward toward the cornea causing damage. With increasing numbers and longer follow-up, his early enthusiasm soured. By the end of the decade, Barraquer had come to regard IOL implantation as a sin of his youth and withdrew his support for the procedure.⁷

Throughout the 1960s and the early 1970s, the IOL was anathema in the United States. Only a few surgeons — primarily Choyce in Britain with the anterior chamber design and Binkhorst in Holland with the iris clip lens — openly advocated continued implantation. In the United States, IOL implantation became “closet surgery” without public champions. The subject was rarely, if ever, discussed at academic centers. IOL implantation was held to be equivalent to malpractice.

Renewed interest in implant surgery was slow. When the interest in IOLs renewed, it rested primarily on the concepts of C. D. Binkhorst. Few surgeons had had any experience with iris-supported lenses in the 1950s. Despite strong opposition, Binkhorst continued to implant his iris clip lens, reporting favorably and sharing his results.

The Russian surgeon, Fyodorov, began modifying Binkhorst lenses in the early 1960s and eventually commercialized his “Sputnik” design later in the decade. A small group of North American surgeons, who were stimulated by Binkhorst, began implanting iris-supported lenses in 1967. However, the profession as a whole remained hostile toward IOLs. In 1969, a temporary moratorium on lens implantation was declared in the Miami area, which had been one of the more active centers for implantation at the time.

Beginning in 1967, Binkhorst began advocating a return to extracapsular surgery after deciding that capsular adhesions may help to stabilize his implant. Binkhorst developed and promulgated a rationale for extracapsular surgery that included the concept of a barrier effect for the capsule that steadied the entire architecture of the eye.² For extracapsular surgery, Binkhorst eliminated the anterior loops from his iris clip lens to produce an iridocapsular lens, which he believed gave superior results. Although some of his American supporters were slow to follow, Binkhorst helped pave the way back to extracapsular surgery.

The Acceptance of Cataract Surgery

A major turning point in the acceptance of IOLs came in 1974. A large group of American ophthalmologists traveled to the Netherlands to observe Binkhorst and returned home eager to transform cataract surgery in America into a pseudophakic procedure. Shortly thereafter, the American Intraocular Lens Implant Society (the forerunner of American Society of Cataract and Refractive Surgery) was formed to support and develop the practice of IOL implantation in this country. American manufacturers began making IOLs to meet the ever-increasing demand for them in America. By 1975, it was apparent that implant surgery had received sufficient professional acceptance to allow the procedure to become widely available.

Why had this sudden shift in attitude toward the IOL occurred in the mid-1970s? No significant change in IOL technology had occurred in more than a decade to justify such an abrupt change in attitude. The Binkhorst iris clip lens had undergone only minor modifications since the late 1950s. Peter Choyce’s anterior chamber lens, which would shortly surpass the Binkhorst lens in popularity, had not changed since 1963 with his Mark VIII design. The change did not result from a new IOL design or material. Rather, there was a transformation in cataract surgical technique, and in the socioeconomic environment surrounding cataract surgery.

By the end of the 1960s, the use of ophthalmic microscopes in cataract surgery was increasing. Fine sutures had become available. Charles Kelman introduced phacoemulsification in the early 1970s. The advantages of phacoemulsification — a smaller wound and quicker postoperative rehabilitation — were effectively promoted. Interestingly, the extracapsular nature of phacoemulsification was not initially appreciated. Early phaco surgeons even attempted to remove the capsule at the end of the procedure, thereby converting phacoemulsification into a small-incision intracapsular operation.

A few dexterous surgeons, many of whom were previously unknown, built large cataract practices on the basis of their phacoemulsification skill. Meanwhile, intracapsular surgeons who were reluctant to embrace the new technique, often for legitimate and cautious reasons, watched their practices decline.

IOL technology was attractive to surgeons who were looking for an alternate route back to the leading edge of ophthalmology. Some surgeons hoped to bypass the taxing learning curve of phacoemulsification. Because insertion of these early implants required a larger wound, they argued there was no advantage to phacoemulsification. But the phaco surgeons also embraced IOL technology. Already enamored by new technology, they saw a natural marriage between phacoemulsification and the IOL. Binkhorst’s embrace of extracapsular surgery supported their case. All ophthalmic surgeons recognized that pseudophakia, if achievable, was far more appealing than aphakia.

These changes in attitude sparked a revolution in cataract surgery. First, this intracapsular, aphakic procedure evolved into an intracapsular, pseudophakic procedure. After progressing into a large-incision extracapsular pseudophakic procedure, cataract surgery finally became synonymous with phacoemulsification, compressible posterior chamber IOLs, and YAG laser capsulotomy. A single generation of ophthalmologists had witnessed this entire evolution.

This revolution in technology was, in part, supported by reform in the health care financing system. In particular, the advent of Medicare coverage not only fueled technological advances, but also paid for the increase in surgical volume occasioned by the success of this new technology. In this new environment, the business and medical communities began to interact in ways that were unprecedented.

Nowhere was this interaction better exemplified than in the newly burgeoning IOL industry. Well-known surgeons were sought out to champion the virtues of new lenses, extol particular brands, and train others in the new technology. The IOL wars were not confined solely within the ophthalmic profession. Patient advocacy groups entered the controversy. Some factions, notably the Health Research Group led by Sidney Wolfe, a disciple of Ralph Nader, strongly opposed lens implantation as being unproved and dangerous. Reports of serious complications led California governmental authorities to briefly attempt to block lens implants in that state.

The pros and cons of IOLs were then debated in the halls of Congress. Actor Robert Young, who had undergone successful implant surgery, was recruited to testify in support of IOLs. Eventually, a compromise was reached and IOLs were to be classified as a drug. They were placed under the control of the U.S. Food and Drug Administration (FDA) starting in 1978. Even though IOLs had not yet been approved as being safe and effective, all ophthalmic surgeons were allowed to continue their use as part of a controlled investigation. This FDA study was perhaps the largest controlled medical trial ever undertaken.

IOLs achieved FDA approval after 1980 starting with the Choyce Mark IX Anterior Chamber Lens and the Shearing Posterior Chamber Lens.

IOL Design

In 1975, lens designs were based primarily on the concepts of C. D. Binkhorst.⁸ Binkhorst was lionized at the first meeting of the American Intraocular Implant Society with the Binkhorst Medal Lecture Series named in his honor. However, the popularity of Binkhorst lenses soon began to wane, with many surgeons noting significant complications. These included pseudophakodonesis, iris tears, and frequent dislocations (aggravated by an unfortunate decision by many lens manufacturers to use metal as a loop material).

Attention soon shifted to the Choyce Mark VIII anterior chamber lens. Gerald Tenant was particularly effective in promoting it and later modifying it. The advantages of easy insertion and apparent secure fixation that surgeons had previously enjoyed in the 1950s were rediscovered. The cycle of the 1950s, however, soon repeated itself. Despite the fact that Choyce Mark VIII lenses were designed and manufactured better than earlier anterior chamber lenses, complications began to occur.

The uveitis-glaucoma-hyphema (UGH) syndrome was described by Thomas Ellingson in 1978.⁹ In contrast to the 1950s, however, these complication rates never reached the point of blocking further development. Instead, debates raged over such questions as whether European lenses were superior to those of American manufacturers, whether lathe cut lenses were better than injection molded lenses, and whether anterior chamber designs would prevail over iris supported lenses. Minor changes in design were fiercely contested.

Attention was redirected to the posterior chamber as a site for implantation in late 1975. John Pearce implanted a rigid posterior chamber lens of a tripodial design similar to a foreshortened version of Ridley’s anterior chamber lens.¹⁰ Because the lens was too short to achieve fixation and centration at the time of surgery, Pearce sutured the lens superior to the iris hoping that the lens would later become fixated to the capsular bag. Eric Arnot and James Little made a larger square-shaped rigid lens hoping to achieve better centration and fixation without suturing. Because it was more difficult to insert, it was primarily recommended for use in specialized cases, such as patients with glaucoma.

In 1976, I designed the first compressible posterior chamber lens which I began implanting the following year. My concept was based upon recognizing that there were two conflicting goals. On one hand, there was the desire to keep the lens small so that it could be inserted easily through the pupil into the posterior chamber. On the other hand, there was the need to have a lens long enough to achieve immediate centration and fixation.

Rather than make the overall lens size a compromise between these two conflicting goals, as had been done in the past, I sought to alleviate the problem by using open-looped flexible haptics. In this way, the lens can be made small enough for easy insertion but would spring open once inside the posterior chamber to achieve centration and fixation. The Shearing posterior chamber lens became the first posterior chamber lens to achieve widespread commercial acceptance.

Open loop, compressible posterior chamber lenses based on the Shearing concept, but with varying loop shapes, reached overwhelming predominance by the early 1980s. Richard Kratz recommended that the haptics be angled slightly forward to prevent pupil capture of a forward-displaced optic. Modified J-loops, as promoted both by Kratz and Robert Sinsky, were particularly popular for a time. In more recent times, the modified C-loop design has been the most popular.

The introduction of YAG laser by Daniel Aron-Rosa in 1980 eliminated the need for surgical discission of an opacified posterior capsule. The last major objection to extracapsular technique had been overcome. The YAG laser allowed a safe capsulotomy to be performed without entering the eye. In the early 1980s, most surgeons still used posterior chamber lenses in combination with standard extracapsular surgery.

Improvements in phacoemulsification equipment and technique led to this technique’s becoming more popular by the end of the decade. With foldable posterior chamber implants, phacoemulsification finally became the dominant procedure by the 1990s. Similarly, improvements in surgical technique, culminating in the introduction of capsulorrhexis, eliminated earlier debate about whether posterior chamber lenses could preferably be placed in the capsular bag as opposed to in the ciliary sulcus. Capsular fixation of IOLs became universally accepted. Capsulorrhexis and secure capsular fixation have almost eliminated pupil capture.

In 1984, foldable silicone IOLs were introduced by Tom Mazzocco to achieve smaller wounds. Today, surgeons can use clear corneal incisions in the 3-mm range. Mazzocco’s lenses were initially of the plate haptic “taco” design without loops. Shortly thereafter, three-piece open loop designs were also developed. In the 1990s, materials other than silicone, including “soft PMMA,” became popular for open looped, foldable posterior chamber IOLs.

Foldable posterior chamber IOLs are now the preference in the United States. However, traditional nonfoldable PMMA IOLs with compressible open loops are still widely used in developing areas of the world because these IOLs are considerably less expensive. Although nonfoldable lenses require larger incisions compared with foldable lenses, they can still be inserted through wounds that do not require sutures.

References

1. Ascher KW. Prothetophakia two hundred years ago. Am J Ophthalmol. 1965;59:445-446.

2. Nordlohne ME. The Intraocular Lens Development and Results with Special Reference to the Binkhorst Lens, 2nd ed. The Hague: Dr. W. Junk b.v.; 1975:14-17.

3. Woods AC. The adjustment to aphakia. Am J Ophthalmol. 1952;35:118-122.

4. Ridley H. Intraocular acrylic lenses — past, present and future. Trans Ophthalmic Soc UK. 1964;84:5-14.

5. Kwitko ML, Kelman CD, eds. Intraocular lens implantation: The Beginnings: The History of Modern Cataract Surgery. The Hague: Kugler Publications; 1998:35-52.

6. Choyce P. Intraocular Lenses and Implants. London, H K Lewis & Co. Ltd; 1964.

7. Barraquer J. Trans Ophthalmic Soc UK. 1964;79:393.

8. Binkhorst CD. Pseudophakia: Intracapsular or extracapsular technique? In: Kwitko ML, Kelman CD, eds. The History of Modern Cataract Surgery. The Hague: Kugler Publications; 1998;69-74.

9. Ellingson FT. The Uveitis-Glaucoma-Hyphema Syndrome associated with the Mark VIII Anterior Chamber Lens Implant. Am Intraocular Implant Journal. 1978;4:50.

10. Pearce JL. New lightweight sutured posterior chamber lens implant. Trans Ophthalmol Soc. 1976;96:6.