About four years ago, surgically implanted “contact lenses” —also known as phakic intraocular lenses—were poised to revolutionize refractive surgery. In September 2004, the FDA approved the Verisyse (AMO), an iris-fixated lens, for correcting myopia in the –5 to –20 diopter range. In December 2005, the Visian ICL (Staar Surgical), a posterior-chamber implant, which is situated behind the iris and in front of the natural crystalline lens, received FDA approval for myopic patients in the –3 to –20 D range. The stage was set to transform the industry.
Fast forward to 2008. Despite the fanfare, it has become increasingly obvious that phakic IOLs have not experienced the surge of popularity or acceptance once anticipated. Both the public and ophthalmic practitioners have been slow to embrace this technology, leading to retrospective scrutiny of what happened and speculation about the future of implantable contact lenses.
Richard L. Lindstrom, MD, adjunct professor emeritus at the University of Minnesota in Minneapolis/St. Paul, pointed to two recent advances that have taken the steam out of phakic IOLs. “First, with the advent of customized wavefront and iris registration combined with the introduction of more sophisticated lasers, LASIK itself has become better,” Dr. Lindstrom noted. “In addition, with femtosecond laser technology (IntraLase), we can create a thinner flap, giving us the ability to be more aggressive with LASIK. This has made LASIK a more attractive alternative for patients.”
On the flip side of the coin, Dr. Lindstrom continued, the Visian and Verisyse remain the only two FDA-approved phakic lenses. While more surgeons have been trained to implant these phakic IOLs, no major advancements in lens technology have occurred to this point. “Without a doubt,” Dr. Lindstrom said, “the refractive surgery market as a whole has been pretty stagnant in the last few years, with surface ablation the only segment gaining ground. Phakic IOLs are not alone among techniques that have not experienced much growth.”
Patients vote with their eyes. The fact that adoption of phakic IOLs seems to have stalled does not surprise Dr. Lindstrom because “patients have a vote in the decision.” Although a patient with –15 D of myopia would more likely choose the phakic IOL, the decision is not as clear-cut for patients in the –8 to –12 D range. Most would rather have surface ablation for a couple of reasons, Dr. Lindstrom explained. “First is the cost: $2,000 per eye for laser ablation vs. $4,000 per eye for a phakic IOL. Second, they perceive LASIK surgery as less invasive. And while the quality of vision may be better with a phakic IOL, there is enough quality in LASIK vision to make them happy. So they opt for the laser surgery.”
Focus Turns to Long-Term Safety
Stephen S. Lane, MD, in private practice in St. Paul, Minn., has been a firm supporter of phakic IOLs since they were first introduced, noting that, from a safety perspective, “phakic surgery involves the ‘addition’ of a lens, whereas LASIK is a ‘subtraction’ procedure where we are actually removing tissue. Thus, phakic IOLS do not carry the inherent problems related to cornea surgery; by adding a lens, the optical system remains intact.” He explained that in the last few years, some of the safety issues have, in fact, been addressed and that surgeons are feeling better about them.
Show me the data. Yet what is lacking are studies on the long-term safety of the technology, a challenge that will only be solved with time. “The safety issues are straightforward,” Dr. Lane noted. “They include problems associated with cataracts; possible endothelial cell loss and resulting endothelial decompensation; and development of glaucoma.” In addition, there are safety issues with the procedure itself and potential problems related to the materials and designs of the lenses, according to Dr. Lane. “More phakic IOLs are in the pipeline, and we are taking the lessons from the past to create better lenses for the future.”
One of those lenses currently under development is Alcon’s angle-supported anterior chamber IOL, which is in phase 3 clinical trials and was the subject of several presentations at the 2007 Annual Meeting. This foldable hydrophobic acrylic material “is very straightforward to implant, utilizes a familiar injector system, and requires a 3-mm incision that is sutureless,” Dr. Lane explained. “It involves a technique and technology that surgeons have used before.”
Diopters: How Low Can You Go?
Interestingly, the current debate focuses not so much on safety as it does on patient selection. Dr. Lindstrom noted that the generally accepted refractive surgery guidelines call for LASIK in patients with –1 to –8 D, and phakic IOLs in –12 to –20 D. Patients between –8 and –12 D fall into a “gray area.”
So where to draw the diopter line? “Obviously, phakic IOLs are most likely the better alternative for high myopes given that LASIK is not a viable alternative,” Dr. Lane said. “However, while some may say that a –10 diopter patient is a good candidate for phakic IOLs, other doctors may bring that level down to –6 diopters. Some may feel that from a safety standpoint, that patient is better served having LASIK. The key question becomes how low can that diopter level go for phakic IOL surgery to maintain a safety profile equal to LASIK. I believe that if you develop better designs, and as the safety becomes better known and established, that you will see a gradual acceptance of phakic IOLs for lower powers, not just the –14 or –15 myope.”
The Search for Something Better
Indeed, there continues to be a need for phakic IOLs better than the two current lenses, according to Dimitri T. Azar, MD, director of the Illinois Eye and Ear Infirmary at the University of Illinois in Chicago. A 2007 edition of a book that he co-edited, Refractive Surgery,1 devotes 12 out of 45 chapters to phakic IOLs and related topics. He noted that “the phakic IOLS approved by the FDA have good qualities, but one can always ask, ‘Is there a better version that combines the best qualities of both lenses?’”
The dream lens. For Dr. Azar, the ideal phakic IOL is easily inserted, removed and exchanged; does not require a large wound; can be fixated adequately without causing pressure on the tissue on which it is fixated; has a relatively thin profile and does not contact adjacent tissue; is made from biocompatible material that does not incite inflammation; has an optical zone large enough to minimize glare; boasts a design that would include optical characteristics to avoid spherical aberration; is affordable; and involves surgery that can be done with relative ease and without the need for special operating room equipment.
“No current phakic IOL has all of these characteristics, but we can use them as a baseline in developing the next generation of lenses,” Dr. Azar said. “Currently, the patients who opt for phakic IOL surgery do so because alternatives are not available for their particular profile. For example, high myopes or those with corneal scarring run greater risks with LASIK than with phakic IOLs.”
Dr. Azar expressed optimism that the industry will do better. “Phakic IOLs were approved well after the acceptance of LASIK and PRK, and those technologies had a lot more time to develop,” Dr. Azar said. “Improvements in this technology will come. For example, currently, phakic IOLs cannot correct astigmatism, but I predict that down the line lenses will be able to do that. The technology is there. Further, as the safety of these lenses gets established and the initial learning curve is overcome, I believe more doctors and more patients will choose phakic IOLs at lower degrees of myopia such as –5 and –6 diopters. That is when you will see more doctors interested in implanting phakic IOLs.”
The Treatment Continuum
Phakic lenses are designed for patients who are prepresbyopic and maintain the natural accommodating ability of their own lens. “Most of my myopes who are age 40 with –12 diopters can do well with a phakic IOL,” Dr. Lindstrom pointed out. “Then when they develop a cataract, we can do surgery and switch them to a good multifocal, accommodating or monovision lens. This is in contrast to the other alternative for presbyopes, which is a refractive lens exchange. I personally would rather implant a phakic lens, take it out and then do the cataract surgery.”
Dr. Lindstrom added that a growing number of physicians are realizing that refractive surgeons can offer patients a continuum of procedures as their eyes and vision needs change. “We are talking more and more about a lifetime approach where you might go from LASIK or a phakic IOL to conductive keratoplasty monovision, or onto a refractive lens exchange or cataract surgery,” Dr. Lindstrom said. “Phakic IOLs continue to have a viable role in this continuum.”
1 Refractive Surgery ed. D. T. Azar et al. (Amsterdam: Elsevier, 2007).
Dr. Azar reports no financial interests related to this story. Dr. Lane reports interests in Alcon. Dr. Lindstrom reports interests in Alcon, AMO, Bausch & Lomb and Eyeonics.
Come to Cancún
Register now for the ISRS/AAO 2008 Annual Regional Meeting on Refractive and Cataract Surgery, May 29 to 31 in Cancún, Mexico. The meeting is in collaboration with the Asociación Latina de Cirugía de Catarata Refractiva y Segmento Anterior and the Centro Mexicano de Cornea y Cirugía Refractiva. For more information, visit www.isrs.org/cancun.