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Bioptics Update: Correcting Both Lens and Cornea
The implantation of a phakic or pseudophakic lens may be supplemented later with a keratorefractive procedure to reduce residual errors and astigmatism. Here’s a look at the history of bioptics, its early promoters and future potential.
The eye offers surgeons two distinct planes, the lenticular and the corneal, on which to engineer refractive improvements. Sometimes a correction on just one plane is insufficient to achieve clear vision. And so it is that with every intraocular lens implant comes the possible need for a secondary refractive surgery, such as LASIK or PRK, to refine the correction or address any accompanying astigmatism. And as lens implants—especially multifocal, accommodative and phakic—gain popularity across the United States, some experts believe that complementary corrections in the corneal plane will increase as well.
Historically, bioptics involves reducing the majority of the refractive spherical equivalent with a phakic IOL followed by a keratorefractive procedure to correct any additional myopia or astigmatism. More recently, some are saying that bioptics represents a viable treatment option for patients with any type of intraocular lens who have large amounts of corneal astigmatism and high degrees of spherical error.
The value of this dual procedure has not been lost on surgeons such as Andrew I. Caster, MD. Like some of his peers who have focused their practice exclusively on refractive surgery, Dr. Caster plans to undergo training on phakic implants, specifically to learn the surgical skills needed to implant the Visian ICL (Staar). Yet he still harbors concerns. “I am not 100 percent convinced I will be offering this alternative to my patients. I need more data about the rate of cataract formation as well as long-term endothelial cell counts and possible endothelial cell loss,” Dr. Caster said. “But I am well-aware that a good number of these patients will need some type of refractive enhancement. I think that any physician who intends to perform intraocular lens implants must have bioptics as part of his or her practice.”
Bioptics Already at Work
Elizabeth A. Davis, MD, along with her colleagues, has been at the forefront of intraocular lens implants for a number of years. She is intimately familiar with the role bioptics play in today’s ophthalmology practice. “One of the most vivid examples of the need for bioptics is when we implant a phakic IOL. Since this is only available in the spherical format, and there is no toric implant yet available, patients with astigmatism may feel this impacts their acuity postoperatively. As a result, when you implant the phakic IOL, you may need to correct any visually significant astigmatism, and that can be accomplished with LASIK, PRK or LASEK,” Dr. Davis said.
She added that bioptics can also be warranted for pseudophakic lenses. “Following pseudophakic multifocal lens implantation, there is the possible need to adjust the spherical and astigmatic refractive error. In fact, due to the nature of IOL calculation formulas and the variability of patient eyes, surgeons never know if we can achieve perfect vision 100 percent of the time, so the possibility of a secondary keratorefractive procedure needs to be discussed with the patient.”
Vance M. Thompson, MD, has been performing phakic implants for nine years and PRK and LASIK for 14 years. He was actively involved in the FDA trials for the Verisyse phakic IOL (AMO). Astigmatism is a concern with this lens, as it only addresses extremely high levels of myopia, not astigmatism. Consequently, during the FDA trials, Dr. Thompson was able to correct a patient with 24 D of nearsightedness without needing to do a secondary keratorefractive procedure, but another patient who required a correction of 18 D of nearsightedness had a residual 4 D of astigmatism. The nearsightedness was addressed with the IOL, and Dr. Thompson corrected the astigmatism several months later using LASIK.
GET USED TO IT. Dr. Thompson views bioptics as an inevitable part of many IOL implants. “I consider that almost every phakic implant case can potentially become a bioptics procedure,” he said. “If patients are not fully corrected with the implant, then we perform an enhancement. For example, if I am pleased with the spherical equivalent but there is leftover astigmatism of less than 1.5 units, I am comfortable with astigmatic keratotomy or a laser fine-tune in the form of PRK or LASIK.”
Pausing for Perspective
Gregory J. Pamel, MD, has a different perspective of bioptics. He feels that at this point in the evolution of refractive surgery, it is premature to focus on bioptics. “Truthfully, in my experience I have not found it necessary to treat my phakic IOL patients with additional LASIK surgery. The accuracy of the Verisyse lens implant coupled with the high satisfaction rate of patients receiving the implant makes additional LASIK on these patients a rare necessity. Of the 150 phakic IOL cases I have done, one patient required LASIK after the procedure. So, from my perspective, bioptics is not something that has really become necessary so far in this group of patients.
A GROWTH INDUSTRY. Nevertheless, noted Dr. Pamel, “This will inevitably change, as patients who’ve received an implant age and their prescriptions change, and as a wider variety of implants continue to gain in popularity.”
Like Dr. Davis, he does not see an arbitrary distinction between phakic and pseudophakic components. “Bioptics should probably be redefined,” he said. “Initially, bioptics was more narrowly applied to corneal surgery after phakic lens implant surgery to treat residual myopia and astigmatism. Now, bioptics will be used more frequently in the pseudophakic eyes to treat residual refractive error after cataract or clear lens surgery. So, while the term bioptics was originally applied to phakic IOLs, it really has evolved to encompass all IOLs.”
Two Corrections, One Refraction
The concept of bioptics was introduced about a decade ago by Roberto Zaldivar, MD, of Buenos Aires. He had done extensive research with phakic IOLs and developed the concept of bioptics to address the shortcomings of the implants. His work drew the attention of Jonathan M. Davidorf, MD, who joined Dr. Zaldivar in Argentina in 1996 to investigate the newest refractive surgical techniques.
“At the time,” Dr. Davidorf recalled, “I was impressed that we could treat such high levels of refractive error so accurately. Bioptics is a way to provide patients with the largest optical zone possible given their refractive error.” Drs. Zaldivar and Davidorf worked closely together and subsequently published the original bioptics article in 1999.1
SPLITTING THE DIFFERENCE. In that initial work, Drs. Zaldivar and Davidorf analyzed the results of 67 extremely myopic eyes with a posterior chamber hydrogel-collagen plate phakic IOL. The eyes then underwent planned, secondary LASIK. The authors note, “We termed the two-part, phakic IOL-LASIK procedure bioptics, because the optical correction is split between two planes: the ciliary sulcus plane and the corneal plane.”
In the article, the authors pointed to two important “theoretical advantages” over phakic IOL or LASIK alone. “First, because the optic of the IOL and the effective optical zone following LASIK both diminish in diameter with increased levels of attempted myopic correction, we were able to maximize the optical zone of each by invoking both procedures.”
Second, the authors surmised that the predictability of the results would improve because LASIK is invoked once the refractive error has been substantially diminished, allowing for less spectacle-induced minification, and thus more accurate post-IOL refractions.
“Simply put,” explained Dr. Davidorf, “the data entered into the laser are just as reliable as for a standard myopic LASIK patient, even though the bioptics patients, prior to ICL [implantable contact lens] implantation, may have had 20 diopters of myopia with 3 or 4 diopters of cylinder.”
EFFECTIVENESS CONFIRMED. Their hypotheses turned out to be correct. In the initial 67 eyes that received the phakic IOL, the mean preoperative spherical equivalent refraction was –23 ± 3.6 D and the mean refractive cylinder was 1.5 ± 1.21 D. After bioptics, the mean postoperative spherical equivalent refraction was –0.2 ± 0.9 D and mean refractive cylinder was 0.5 ± 0.5 D. The series demonstrated excellent short-term stability of bioptics-treated eyes to six months.
“This initial research validated a role for bioptics in the ophthalmologist’s armamentarium,” Dr. Davidorf noted. “We anticipated that more types of refractive IOL procedures, not just phakic IOLs, would gain increasing acceptance, thus requiring an expanded use of bioptics.” Almost a decade later, these predictions have held true, with bioptics continuing to inform any discussion regarding refractive IOL procedures.
SAFETY CONFIRMED. Close to 10 years after Drs. Zaldivar and Davidorf demonstrated the safety and efficacy of the bioptics concept, surgeons new to the approach may question whether performing a secondary refractive procedure—whether it is LASIK, PRK or astigmatic keratotomy (AK)—is safe after IOL implantation with today’s lenses.
Dr. Thompson responded with a confident yes. Case in point: The Verisyse phakic IOL is an anterior chamber lens placed behind the cornea and on top of the iris. Because of this positioning, noted Dr. Thompson, surgeons were initially worried that the implant could touch the corneal endothelium during a keratorefractive procedure and cause damage to that layer. “However,” explained Dr. Thompson, “studies have subsequently shown that you can do LASIK flaps or PRK and you don’t have to worry about the implant touching the endothelial layer. In essence, there is nothing different about doing PRK, LASIK or AK on top of a phakic implant, or on top of a nonphakic implant, for that matter.”
From Lens to Cornea, Slowly
Dr. Pamel noted that one of the most important aspects to consider when doing bioptics is to wait for a stable refraction before doing the secondary procedures. “With phakic IOLs, I believe that additional surgery should be done no sooner than three months postoperatively, and most of the time, you may want to wait between six and 12 months longer to do another procedure just so the eye can stabilize,” Dr. Pamel said. “In patients who receive an accommodative or multifocal implant, I believe waiting three months is a reasonable time. It is imperative that the wound from the corneal incisions heals.”
Dr. Davis also agreed that waiting three months is recommended for a secondary procedure, always ensuring that the eye is stable from the first procedure before proceeding to the secondary procedure.
SUTURES OUT, THEN WAIT. In addition, Dr. Thompson stressed that “if stitches were used for incision closure, you want those to be out three or four months before the secondary surgery to ensure that they are not causing the astigmatism.”
On the other hand, Dr. Davidorf noted that with implant incisions becoming smaller, “the integrity of a 3-millimeter or smaller clear corneal incision is sufficient that at four to six weeks we can perform LASIK—something that I could not have anticipated 10 years ago when we developed the bioptics concept.”
GOOD CANDIDATES AND NOT-SO GOOD. The best candidates for bioptics, according to Dr. Davidorf, are those requiring more than 15 D of correction, and/or patients with more than 10 D of myopia and 2 D of astigmatism. “The ICL can take care of the majority of the refractive error, and then we can use LASIK to fine-tune the correction,” he said.
Dr. Davis added that patients who are not candidates for bioptics generally are the same population who are not candidates for LASIK or PRK, for example, those with thin corneas, or those with topographies suspicious for keratoconus or pellucid marginal degeneration.
ONE VISION, TWO BILLS? Since bioptics involves two separate procedures, patient costs are inevitably higher than doing just one procedure. “The pricing varies,” Dr. Davidorf pointed out. “You need to consider the cost of the phakic IOL and the cost of LASIK. Many practices may discount the LASIK part of the procedure since the patient already underwent a phakic IOL implant, but generally speaking, I would expect bioptics to cost substantially more than phakic IOL surgery alone.”
Both Drs. Davidorf and Davis stressed the importance of informing patients up front about the extra costs of the two procedures. Dr. Davis said, “I believe that as long as they are aware of the potential for bioptics and the extra costs up front, there will not be any issues or surprises with patients down the line.”
The Look of the Future
Dr. Pamel predicted that with more people undergoing various lens implants, more and more patients will require LASIK or other keratorefractive procedures to refine outcomes.
“One of the amazing aspects of the bioptics story,” noted Dr. Davidorf, “is that this technology is actually a 10-year-old concept, yet it has been only recently that surgeons in the United States had the ability to perform phakic IOL surgery. Consequently, it is only now that we can really utilize bioptics as the technique was initially conceived.”
BIOPTICS, TOO, SHALL PASS? Yet newer technology on the horizon may one day make bioptics obsolete. Dr. Thompson pointed out that researchers are working toward creating the “ultimate phakic IOL,” in which the implant is “so accurate, including the sphere and cylinder, that we will be able to hit a home run every day and thus eliminate the need for bioptics.”
Dr. Davis went a step further, predicting that if laser-modifiable IOLs ever become successful, the two procedures that constitute bioptics will become one. “This is an IOL that is placed in the eye and then modified with a laser, bypassing the cornea altogether. The introduction of this type of IOL would be the ultimate procedure, eliminating the need for bioptics.”
“Newer IOL models, laser-adjustable or otherwise, will decrease the need for bioptics, but not eliminate it,” Dr. Davidorf said.
“For the more extreme refractive errors, bioptics will still allow the advantage of yielding a larger functional optical zone than any phakic IOL alone, by splitting the correction between the iris and the corneal planes.” For the time being, as refractive implants become more popular, inevitably the need for bioptics will increase. “Without a doubt,” said Dr. Davidorf, “the concepts go hand-in-hand.”