Presbyopia correction will set a new standard for cataract surgery

As the IOL revolution enters phase 2, the focus turns to correction of reading vision.

Issue: July 1, 2005

ByWilliam F. Maloney, MD

William F. Maloney, MD [photo]
William F. Maloney

Phase 1 of the IOL revolution spanned some 50 years, transforming cataract surgery and the surgeons who perform it. By steadily shifting greater emphasis onto the refractive benefits of cataract surgery, the IOL forced surgeons to continually transform their skills. As the new cataract surgery moved inexorably toward its full refractive potential, surgeons faced a Darwinian struggle to continually acquire the requisite new skills. The daunting transitions to the operating microscope and phacoemulsification were followed by the more recent adoption of the temporal clear-corneal incision and astigmatic keratotomy, along with noncontact A-scan techniques.

Because an entire generation of newly redefined “refractive” cataract surgeons targeted distance emmetropia as their goal, today’s surgeons, armed with those same skills, routinely achieve uncorrected distance vision almost at will. This was a fitting finale to phase 1 of the IOL revolution – thus far the most remarkable period of collective achievement in the history of ophthalmology.

The IOL revolution has, naturally enough, set its sights on reading vision as the goal for phase 2. Long-term success depends in large part on whether this generation of surgeons is prepared to pay the price that their predecessors did. Different and somewhat untraditional new skills are required when reading vision is added to the refractive cataract equation. Just as with the distance vision effort, presbyopia correction is a comprehensive, multifaceted approach that goes beyond the intraoperative surgical events and the IOL itself. There can be no shortcuts if we are to get exactly the right reading vision range that is best for each patient, and as I have said repeatedly in these columns, “exactly right” is rapidly becoming the metric of presbyopia correction.

Accuracy redefined

$OSN Lens-Based Refractive Surgery [logo]$ The process of presbyopia correction starts well before the surgery itself. Consider, for example, the IOL calculation aspects. Regardless of how great the underlying distance refractive error, we must be able to consistently arrive at the point where phase 1 has brought us – exact distance emmetropia. This is our zero refractive starting point, the fundamental foundation upon which the additional accommodative effect is “added.” Any variation from our targeted distance refraction will be magnified when we turn to the reading correction, regardless of the IOL we use. This, of course, is no different than the formula for a successful spectacle presbyopia correction – emmetropia plus the reading “add.” Unfortunately, achieving emmetropia with an IOL to this degree of precision is hardly the routine matter it is with spectacles, and surgeons are not yet sufficiently involved in this critical preop process.

Although we increasingly hear that accurate IOL calculations are important, this broad generalization masks the depth of the challenge facing phase 2 surgeons. This element of presbyopia correction is central to success and simply too important to be left to anyone but the surgeon. If you are serious about consistently successful lens implant presbyopia correction, you need to become intimately involved with the entire IOL calculation process. You need to develop a keen instinct for when things are not right at any stage, and you need to acquire state-of-the-art, noncontact instrumentation. An experienced technician was adequate for IOL distance correction during phase 1, but the new metrics of presbyopia correction demand that you now approach this process as you would any integral part of your surgery. I am well aware that this represents a major departure from the status quo in most surgical practices. Hopefully, some supporting statistics will help to convince you that its importance requires your participation.

I think we all would agree that if our IOL calculation resulted in a correction from +3.5 D to +0.5 D, we could expect a highly satisfied patient and congratulate our technician on an accurate distance refractive correction — accurate for distance vision, but likely not accurate enough for reading. This +0.5 D of hyperopic defocus will directly reduce our available reading “add” by that amount. Presbyopic IOLs today typically deliver around 2 D of accommodative “add” effect. Against this metric, this hyperopic IOL calculation result of just 0.5 D is a significant calculation error of 25%. Suddenly our 2 D available reading “add” is reduced to 1.5 D and will likely be insufficient to meet our patient’s expectations, especially if he has chosen full reading capability as a surgical goal. The sobering fact is that our technician’s good IOL outcomes for distance correction are no longer good enough when reading correction is added to the equation.

I highlight this IOL calculation process in particular because it represents the type of paradigm shift that phase 2 will demand of this generation of surgeons. Presbyopia correction succeeds or fails primarily in the planning, and the surgeon must be intimately involved in every phase of that process. We need to develop these preop planning skills with the same determination that our predecessors met the challenge of phaco.

Other examples of the “soft skills” essential to presbyopia correction that we have previously described in this column include the elements comprising the patient’s presbyopia profile such as pupillography, the amount of myopic defocus each patient can readily tolerate, the interocular defocus threshold, ocular dominance and blur suppression capacity. No less important are the lifestyle elements of each profile, such as reading habits, night driving needs, spectacle use and each patient’s unique reading goals, which typically vary widely.

“Real” reading

The IOL industry has not emphasized these surgical planning skills essential to presbyopia correction. The companies would prefer that you rely solely on their particular IOL for your success. Their podium infomercials point to a data pool of patients who are satisfied because they can now “read” as evidence of their particular IOL’s superior technology. I have seen several of these patients. I suppose many of you have, too.

Since any reading focus is an important improvement when previously there had been none, most of these patients were initially pleased with the restoration of even limited near-focus capability. However, that changes when they inevitably encounter a friend or colleague whose presbyopia correction has restored full reading capability as a result of, for example, the additional accommodative effect from just the right amount of myopic defocus. This unlimited zone 1 reading result — “real” reading, as one patient recently called it — is now usually possible only through the type of comprehensive, careful preop assessment I have been advocating in this column during the past 2 years.

That is the price presbyopia correction is going to demand. The transition to such a nuanced, multifaceted preop process will no doubt feel uncomfortable and bewildering to surgeons at first. But I assure you that the first time you assess all of these variables exactly right for your patient, you will know that the cost of admission to phase 2 was worth it.

Next month

Instrumentation for assessing the preop presbyopia profile.

For Your Information:
William F. Maloney, MD, is head of Eye Surgery Associates of Vista, Calif., and a well-known teacher of cataract and lens-based refractive surgery techniques. He can be reached at 2023 West Vista Way, Suite A, Vista, CA 92083; 760-941-1400; fax: 760-941-9643; e-mail: maloneyeye@yahoo.com. In the interest of objectivity, Dr. Maloney has no financial interest in any ophthalmic product and has no financial relationship with any ophthalmic company.