The remarkable evolution of cataract surgery makes the past 20 years a ‘golden age’
As part of our celebration of the 20th anniversary of Ocular Surgery News, our Section Editors look at how things have changed. This month, William F. Maloney, MD, on cataract/IOL.
The techniques and technology used in cataract surgery have been completely revolutionized during the past 20 years. We are all aware that during this rich, exciting and highly productive period, a series of innovations converged to transform cataract surgery from a 45-minute extracapsular extraction procedure to clear corneal phacoemulsification and foldable IOL implantation capable of accurately correcting virtually any existing refractive error.
But why did this happen? What driving force led to this unique moment in time that produced such unprecedented advances? What happened to render a good ECCE procedure suddenly no longer good enough? The answer is important for us as we look back over the past 20 years, not only to celebrate this golden age of cataract surgery but also to try to put it in proper historical perspective.
First we must appreciate the fact that these innovations did not occur by chance. The story of cataract surgery over the past 20 years is the story of a series of interdependent innovations that were being silently driven to the forefront by the dawn of a new paradigm for cataract surgery. Those familiar with Thomas S. Kuhn’s 1962 text, “The Structure of Scientific Revolutions,” will recognize his now-familiar phrase “paradigm shift” as the indispensable catalyst for any period of significant progress within a scientific (or medical) community.
As the paradigm begins to shift, innovations that drive the new paradigm forward seem to line up waiting to be “discovered” by those who can suddenly “see” the innovation’s unique potential, but only within the context of the new paradigm. Those few who initially adopt these innovations are thus inevitably viewed with suspicion as opportunistic outsiders, and essentially irrelevant, by those who continue to adhere to the old paradigm. Thus Kuhn predicted that no paradigm shifts without a struggle. Cataract surgery was certainly no exception.
Kuhn’s paradigm shift has become part of our modern culture because it pinpoints one of the all-too-human limitations to progress; we can neither understand nor accept as possible that which we do not yet “see.” We are all indebted to those with the vision to see cataract surgery’s new paradigm, even if dimly at first. Without these gifted and courageous individuals who were willing to stand alone and endure this struggle, the golden age of cataract surgery could never have occurred.
We set the stage for this story with Kuhn’s paradigm shift to emphasize that the particular series of innovations of the past 20 years were not only cumulative but also directional. Their path followed a trajectory that was ultimately to transform the very concept of cataract surgery from an extractive procedure — designed solely to address the obstructive visual impairment of lens opacity — to the new, broader paradigm of refractive cataract surgery we all share today.
This then is the background for our story that rightly must begin not 20 but slightly more than 50 years ago with the first of those visionaries who even then could see the refractive potential of cataract surgery, Harold Ridley.
The first refractive cataract surgeon
The concept of cataract extraction (as opposed to couching) had been a revolution in itself when first performed in 1750 by the French ophthalmologist Jacques Daviel. Two centuries later Ridley, who was being fiercely criticized for performing the first lens implant in 1949, offered the following elegant explanation that is typical of one able to see something in the future that others yet did not.
He stood alone in his own defense and said simply, “By replacing the extracted lens, I have merely completed the operation Daviel began 200 years ago.”
Ridley was able to “see” that removal of the obstructive lens was only part of what cataract surgery could be. Even then, he was able to see its refractive potential, and his lens implant started us on the path toward a procedure that today has achieved a level of refractive accuracy far beyond what he could have imagined.
Indeed, the consistently excellent refractive result of today’s state-of-the-art cataract surgery exceeds even our own recent expectations. The steady improvement in the refractive accuracy of cataract surgery is the result of several advances in the past 20 years that we shall review, but none was more important than phacoemulsification with its small incision, upon which almost every subsequent innovation depended.
In retrospect, phaco was the small-incision gateway through which today’s refractive cataract surgery was eventually to be reached.
Phaco and the small-incision revolution
Although it was initially described in the American Journal of Ophthalmology in 1967, phaco’s time had not then come. A typical visionary, Charlie Kelman was ahead of his time, and for a while so was phaco. From 1967 to 1980 the percentage of cataract surgeries performed by phaco was less than 5%. By 1984, after almost 20 years in existence, phaco was still being used in less than 10% of cataract surgeries.
Although the benefits of the small 3-mm phaco incision were increasingly apparent, the large rigid IOL of the time required an incision of 6 mm to 7 mm. For most surgeons, there was simply no compelling reason to change from ECCE, which was steadily improving with the techniques and teaching of Dave McIntyre and others.
I recall participating at a roundtable on the future of phaco in 1985. I had been trained in phaco during my fellowship with Richard Kratz a few years earlier and was beginning to teach and write about what I saw as a valuable and underutilized technique. Each participant in that roundtable was asked to predict the maximum utilization of phaco in the future. Most believed that it would never exceed 15%. I went way out on a limb and predicted phaco might reach as high as 25% in the coming years.
None of us anticipated what was about to happen. By 1990 phaco exceeded 50% of cases. By 1995 phaco had all but replaced ECCE as it approached 90% usage. Why was a good ECCE procedure suddenly no longer good enough? What had happened to suddenly make phaco an essential element of cataract surgery? The answer is the next chapter in our story. What happened was the foldable IOL, the “Mazzocco Taco.”
Foldable IOL brings refractive benefits
The foldable IOL was conceived for one purpose; to unleash the considerable benefits of the unenlarged 3-mm phaco incision. I know, because I was there at its moment of conception. Midway through my fellowship with Dick Kratz, I was assisting in surgery with Dick’s associate Tom Mazzocco. After a series of five cases of phaco with the rigid IOL of the day, Tom then performed a true small-incision (3 mm) phaco in a myopic patient who did not require an IOL. We both remarked on the significant difference between the two procedures.
“That extra 3 to 4 mm in the enlarged incision really makes a huge difference,” Tom said. “Wouldn’t it be great if we had an implant that was foldable like a soft contact lens that could be inserted without enlarging the 3-mm incision? Hmm, I might work on that,” he said to himself.
About 5 years later Tom unveiled the first foldable silicone IOL and suddenly that good ECCE procedure was obsolete. Within 5 years it would be all but extinct in the United States. Now that the full benefit of small-incision phaco was within reach, more and more of us could begin to see the significant refractive potential of cataract surgery. By 1985, phaco’s time had come and from that point on, cataract surgery was increasingly judged by its refractive results.
The ‘refractivization’ of cataract surgery
It began slowly, but by the end of the period from 1985 to 2000, cataract surgery was refractive surgery. For better or worse, cataract surgery had always had a profound effect on our patients’ refractive status. As this period began we increasingly knew we needed to learn what was required to consistently ensure it would be for the better. The primary extractive aspect of cataract surgery — the phaco process itself — first had to be improved to the point where a significant complication was a rare occurrence.
We looked to the industry to improve surgeon control of the two main components of the phaco process: power and aspiration. Linear and later dual linear gave surgeons control over these parameters, and phaco became more predictable and reproducible.
This technology quickly led to a new generation of “disassembly” techniques in which the nucleus was no longer emulsified but rather manually divided by cracking (and later chopping) into “tip-sized” pieces, which were mobilized and evacuated by phaco-assisted aspiration. Capsulorrhexis led to consistent IOL centration and reduced capsular tears. Viscoelastics vastly improved corneal protection, and by the early-to-mid-1990s, state-of-the-art cataract surgeons could begin in earnest to turn their attention toward refining their refractive results.
In 1995, introduction of the astigmatically neutral clear corneal incision essentially eliminated surgically induced astigmatism, while peripheral astigmatic keratotomy proved capable of treating most existing astigmatism.
Of even more impact were the improvements in IOL calculations. A new generation of formulas, combined with more accurate A-scan techniques, virtually eliminated the 3 D IOL surprise. Indeed, if today’s cataract surgeon takes full advantage of the state-of-the-art IOL calculation techniques currently in use, one can consistently correct virtually any degree of myopia or hyperopia to within 0.50 D of target.
The ability to correct both astigmatic and spherical existing refractive errors with this degree of accuracy was almost certainly never anticipated by Ridley, Kelman or even the many others who more recently have led us to the conclusion of our story. Today’s state-of-the-art refractive cataract surgery is a remarkable achievement by any historical standards. I wrote this article for many reasons, but primarily in hopes it would serve to remind us how fortunate we are to have this procedure at our disposal. As we have seen, it did not come easily, but nothing worthwhile ever does.
More to the story
Our story will not end here. The next chapter is already being written by the next generation of visionaries who are able to see that the trajectory of the pathway we have followed here is rapidly leading us into the refractive arena. This next new paradigm, like all the others, will not shift without a struggle. Nevertheless, as LASIK parameters continue to shrink, refractive lensectomy may well be the next idea whose time has come.
For Your Information:
- William F. Maloney, MD, can be reached at 2023 West Vista Way, Suite A, Vista, CA 92083; (760) 941-1400; fax: (760) 941-9643; e-mail: firstname.lastname@example.org.