Corrective lens implantation for myopia, hyperopia and presbyopia

The techniques are proven and ready. As surgeons, are we ready?

Issue: July 1, 2003

ByWilliam F. Maloney, MD

How important is a name? We have been using several different terms for this particular aspect of lens-based refractive surgery. Replacing the crystalline lens to correct ametropia and/or presbyopia has been alternatively named refractive lensectomy, clear lens extraction, refractive lens replacement and (the trademarked) PRELEX, among others.

Ophthalmologists readily understand the procedure to which all of these terms refer, but not so our patients, for whom the name must clearly differentiate this relatively new approach to vision correction from other corrective surgeries. I use the term “corrective lens implantation” in my own practice because it does just that for my patients. With this name they instantly recognize this technique as a new application of today’s highly successful cataract surgery. And that’s exactly what it is. Unless a genuine consensus emerges for an alternative, I’ll use this term to refer to this lens-based refractive surgery.

We will examine the specific techniques involved in the next several issues before moving on to some new lens technologies on the immediate horizon, such as the accommodative IOL. Today we need to examine the evolution of corrective lens implantation so that we too see this procedure for what it is: not a new technique, but the new manifestation of the remarkable revolution that started with phaco and the IOL.

Paradigm shift

This quotation is from an Ocular Surgery News article in the Focus on Phaco column I wrote in 1991:

“Why after more than 20 years is phacoemulsification suddenly being so widely adopted? Why in a recent survey are more than 36% of us now doing phaco, with estimates for 50% next year? Why is every phaco course filled to capacity with surgeons suddenly eager to learn? In my opinion, the answer is that with the foldable IOL, phaco is now for the first time able to provide the benefits for which it was intended. Cataract surgery is increasingly judged by its refractive results, and those results simply cannot be duplicated by an otherwise very good extracapsular approach.”

The phaco revolution was to reach a crescendo; within 4 years, phaco would totally replace extracapsular cataract extraction (ECCE) with 97% saturation. The answer to the question as to why phaco suddenly became so widely adopted lies beneath the surface.

The shift from ECCE to phaco was actually powered by another underlying shift: a classic paradigm shift. A paradigm is a certain perspective or particular viewpoint that determines how we see something. The paradigm answers the question, “Toward what end is this particular innovation the next step?”

Once a new paradigm — with its particular endpoint or goal — is in place, all subsequent innovations are seen as more or less relevant with respect to this new goal. A particular paradigm is therefore the overarching organizing principle, selectively determining whether a particular innovation is seen as useful and thus accepted or discarded. Those adopted are seen as moving one step closer to realizing the paradigm’s ultimate goal. The series of subsequent innovations needed to bring that goal to full expression then seem to line up waiting to be discovered. Those discarded are quickly forgotten.

At first only the visionaries can appreciate the organizing principle of the new paradigm, so they seem to see the future far ahead of others (Ridley and Kelman surely fit). Since the majority are not yet aware of the new paradigm, these visionaries are derisively rejected as irrelevant or worse by the “ivory tower” establishment. For them, each innovation arrives without its context and is therefore completely misunderstood. Remember the editorial in Ophthalmology decrying small-incision surgery as essentially a marketing gimmick?

Only at the tipping point when a critical number are able to “see it” are the ideas of the visionaries finally accepted (also true in our case). This, according to Thomas Kuhn in his classic text The Structures of Scientific Revolutions (in which he coined the term paradigm shift), is how progress occurs within a given scientific community.

When held up to the period in ophthalmic surgery we are considering, it is a remarkably accurate reflection, and it can be of great help to us here as we consider the immediate future. It provides us with that organizing principle we need in order to see what is next and prepare. Without that, we’ll be out of synch with the progress at hand, constantly feeling, “Every time I find the key, they change the lock!”

So take a look back at the remarkable string of innovations in cataract surgery over the past 20 years, and ask yourself toward what goal has each of these sequential innovative steps been leading us? What is this path’s trajectory, and where does it logically end?

By now, many have already seen the answer. The new paradigm is for cataract surgery to realize its full potential not just as a restoration procedure (to restore vision lost by lens opacity), but also as a corrective procedure (to correct visual impairment due to ametropia). It is only by this new criterion that ECCE fell significantly short of phaco, but suddenly this was the only criterion that really mattered. The new paradigm made it inevitable that ECCE would be totally eclipsed by small-incision phaco.

In 1991, many surgeons rushed to learn phaco. Some came grudgingly, as it was a daunting task for those with no prior experience, but they came nonetheless. The tipping point had been reached and the floodgates opened at a moment of collective recognition that phaco was no longer an option. The new refractive realities made it essential. This is the context for the quote, “Nothing is more powerful than an idea whose time has come.”

As this emphasis on refractive results took hold, the amount of lens opacity necessary for cataract surgery steadily diminished, especially for patients with significant refractive errors. The threshold quickly dropped from 20/100 to 20/40 and then further to 20/30 or 20/25 with glare-related visual impairment. The paradigm had shifted and so did the equation between the extractive and refractive goals of cataract surgery. ECCE — a very successful extractive procedure — was no longer good enough.

New refractive goals

As technology and surgical skills progress, there is increasing emphasis on delivering optimum refractive results in a more formalized corrective approach for those cataract patients interested in the best vision possible without glasses. We discussed this last month in some detail. If you have been considering this, then last month’s column, Refractive Surgery and the Cataract Surgeon, by Medicare compliance consultant Kevin Corcoran, is a must-read.

Eliminating glasses for interested cataract patients is a significant achievement. Few thought it possible a decade ago. However, even that accomplishment is not the goal — at least it is not the ultimate goal — of the refractive gains in cataract surgery over the past 20 years. That lies just ahead across the 20/20 threshold, where cataract surgery no longer requires the cataract.

As in 1991, I expect the floodgates to open in the next years, as this becomes a reality for more and more surgeons. In one sense, this is the reason we all learned phaco, IOL and the many refractive innovations that followed, whether we knew it at the time or not.

The dramatic events of the past 20 years have carried us inexorably to this juncture. All of the necessary techniques and technologies are in place. Are we surgeons able to say the same? Regardless of any new technology that may be on the horizon (and there are many for us to examine in future columns), successful corrective implant surgery will depend primarily upon the individual surgeon’s abilities. These proven techniques require the proven, highly polished skills acquired only from extensive experience. The technique of corrective lens implantation for myopia, hyperopia and presbyopia is poised and ready: are we?

Ready to cross the 20/20 threshold?

This is not a trivial question. Even the most experienced cataract surgeon must take nothing for granted when answering. Although the skills are the same as in state-of-the-art cataract surgery, there is much greater demand placed on the accuracy of results across the 20/20 threshold.

It is one thing to discuss the possibility of eliminating glasses in a patient who also has a cataract, but it is quite another when that cataract is removed from the clinical picture. Performing cataract surgery without the cataract suddenly shifts the outcome equation toward results that consistently must be very near perfect. It requires every surgeon to ask, “Have I prepared enough to be sure that I can expect results at this level on a consistent basis”?

Of course, we must each answer this question for ourselves. In order to cross the 20/20 threshold responsibly, we need to be certain of the answer. You will know that answer when you no longer have to ask yourself the question. What mileposts must we pass to get there? I can tell you those that guided me. I felt I needed to be able to answer each of these questions with a solid “Yes.”

Am I confident that:

The capsule will remain intact?
My IOL selection will result in a postop refraction within 0.25 D of my target (0.5 D for ametropia greater than 8 D)?
I will create no surgically induced astigmatism?
I can surgically reduce any existing astigmatism to less than 1 D on a long-term basis?
I can address presbyopia to this patient’s complete satisfaction?
My target refractive outcome is the proper plan to meet this particular patient’s visual needs and expectations?

Other surgeons would possibly add to this list. These are the criteria I selected. They are readily recognizable to refractive cataract surgeons. Again, the difference is in the level of tolerance for any error. I have used the word “confident” rather than “sure” because surgery will never be an absolute endeavor.

Perfection is not possible for us humans, but we must be prepared to get much closer to it than we have previously. Many of the new technologies on the horizon are designed to make it easier to do that. None, however, will substitute for the surgical skills required.

That is our task. The time is now, as more and more of us are able to “see” that corrective lens implantation — just like phaco in 1991 — is an idea whose time has come.

Next column in August 1:

A detailed look at just what’s needed to meet the above criteria.

Eliminating glasses for interested cataract patients is not the ultimate goal of the refractive gains in cataract surgery…that lies just ahead where cataract surgery no longer requires the cataract.