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2005 to be a watershed year for cataract surgeons
At the OSN Section Editor Summit earlier this year, William F. Maloney, MD, said presbyopia correction will dramatically redefine the “refractive” component of cataract surgery.
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For some time now, the course of development for cataract surgery has been almost entirely determined by refractive considerations. After more than 20 years of incremental improvements, today’s state-of-the-art cataract surgery has become something of a refractive wonder, delivering uncorrected distance vision almost at will. Building on this ability to achieve distance emmetropia, surgeons have, naturally enough, now turned to reading vision correction.
Introducing presbyopia to the refractive cataract surgery equation will affect cataract surgeons to a degree not seen for some time. Most surgeons are not yet sufficiently familiar with the scope of the changes involved. As this year unfolds and patients increasingly ask cataract surgeons to deliver a specific targeted range of uncorrected reading vision, the challenges of successful presbyopia correction will become apparent. Change of this magnitude has not happened since the foldable IOL forced the transition to phacoemulsification more than 20 years ago. 2005 will be the year that the next phase of that IOL revolution — targeting reading vision — begins. It will be remembered as the year most cataract surgeons began to take presbyopia correction seriously, and it will likely prove to be just as dramatic.
More than the IOL
Right now we are in the beginning stages, and typically as with any new technology, surgeons have begun by adopting a preferred IOL and gained experience by asking the question, “Which patients are best for this IOL?”
The next phase of this process is already under way among more experienced surgeons who are now asking the better question, “Which IOL is best for this patient?” This broader, patient-centered approach expands our ability beyond the benefits limited to one particular IOL and allows us to match each patient with the technology that will best deliver his specific reading vision goals. Consistently achieving the expected results in a wide range of candidates demands a major shift of surgeon participation in a part of the process previously relegated to ancillary personnel — preop evaluation and testing. I expect many will initially struggle with this transition since it dissolves many of the boundaries demarcating the traditional domain of the surgeon.
However, if we are serious about achieving wide-ranging success with presbyopia correction, this is an essential shift from the usual approach. The process of presbyopia correction starts well before the surgery itself. The preop assessment is central to success and is far too important to be left to anyone other than the surgeon. We need to develop the critical preop skills of measuring pupillography, defocus threshold, dominance, and blur suppression and especially highly accurate biometry. We also need to become experts at assessing the lifestyle elements of each patient’s presbyopia profile, such as reading habits, night driving needs, spectacle use and specific reading goals, which typically vary widely.
The refractive recalibration
Exact emmetropia is the zero refractive starting point for all presbyopia correction, no matter what IOL is used or how great the refractive error. Hyperopia of +5 D or myopia of –12 D both must be brought to emmetropia, where all accurate presbyopia correction begins. Within the ±2 D range that defines presbyopia correction, an error of just 0.5 D is highly significant.
This establishes a new metric for accuracy in biometry that demands a major commitment to refractive recalibration for cataract surgeons. This process is already under way, as noncontact instrumentation for biometry such as the IOLMaster (Carl Zeiss Meditec) is now used by 35% of cataract surgeons, up from 28% last year.
IOL power labeling outdated
Another glaring anachronism is industry’s current method of identifying IOL power. Little more than 25 years ago, every patient received an 18 D IOL. Advent of the A-scan and calculation formulas in the early 1980s allowed for a more customized IOL power selection, and lens implant power was identified within 0.5 D increments, an acceptable range of error until recent years.
Today, when patients increasingly expect uncorrected distance vision, the fact that the leading cause of malpractice for cataract surgeons is a refractive surprise looms large. As we have seen, when presbyopia correction is added to the equation, an error of 0.5 D can be the difference between success and failure in achieving the expected range of uncorrected reading vision. Yet this range of error — it could be up to 0.9 D in the higher power range — is inherent in the present method used to identify and label the power of each IOL manufactured.
Surgeons are moving rapidly to recalibrate to the new metric of presbyopia correction. More than half now use noncontact biometry, of which 35% use the IOLMaster. Why are we willing to purchase such an expensive instrument (about $25,000)? Because we recognize that we need it to recalibrate to today’s metrics. 2005 must be the year that industry also moves. Manufacturers need to update the accuracy of power identification by including information on the label that we vitally need and that they already have on record — the exact IOL power. The sobering fact is that if you are among the 35% of surgeons using an IOLMaster, the greatest source of refractive error in your cataract surgery is now likely to be the label on the IOL itself. We will be working on this issue in the coming months and report to you in the Lens-Based Refractive Surgery column.
Endophthalmitis/corneal incisions
Other issues important to cataract surgeons that we will be exploring include the reported increased incidence of endophthalmitis. Why is this? Does it have anything to do with the increased incidence of clear corneal incisions? My own view is yes; it does relate to clear corneal incisions, but to the learning curve, not an inherent defect in the incision itself. Remember that there was a dramatic increase in the incidence of capsule rupture as surgeons transitioned from extracapsular cataract extraction to phaco. That proved to be a temporary phenomenon. I suspect we will see this same pattern unfold as surgeons come to understand the degree of architectural precision corneal incisions demand. Given the seriousness of endophthalmitis, this is a matter of some urgency and should be addressed in standardized hands-on training courses, perhaps developed by the cataract sections of both the American Society of Cataract and Refractive Surgery and the American Academy of Ophthalmology.
Wavefront cataract
Two studies on wavefront cataract have recently been published, and I am involved in a third that correlates lenticular wavefront aberrations with cataract formation and subjective visual symptoms. This is potentially an important issue that bears watching, especially as presbyopia correction is increasingly performed on Medicare patients. Whether a given patient is categorized as a cataract or refractive lens exchange candidate is going to be an even more important matter. This technology may help us to correctly identify those patients by redefining what it means to have a visually significant cataract.
Bimanual phaco
Finally, bimanual microincision cataract surgery is still a highly visible issue. Many feel that this is much ado about nothing, driven by marketing and nothing more. In the end, it will be an enduring innovation only if it provides clinically apparent benefits for a wide range of cataract surgeons. That will be determined in time and, just as with the advent of the foldable IOL, will be driven primarily by the type of implants that we have to put through these ultra-small incisions.
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.