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Both patients and physicians benefit when there is more than one good treatment option for a condition, as is now the case with refractive procedures for moderate to high myopia. Still, this situation can present a quandary when the options—phakic IOLs (pIOLs) versus corneal refractive procedures—appear to be well balanced. How does the ophthalmologist decide?
In choosing between these methods, surgeons face a highly subjective patient selection process. Not only is there a multitude of technical and anatomic issues to be weighed, but these factors are often viewed through the lens of an ophthalmologist’s personal preferences.
Currently Available Phakic IOLs
In the United States, only two pIOLs are currently approved by the FDA: the posterior chamber Visian Implantable Collamer Lens (ICL; Staar Surgical) and the iris-fixated Verisyse lens (Abbott Medical Optics), known as the Artisan lens in Europe. So far, U.S. indications are for myopia only, although trials are under way for toric and hyperopic correction. In addition, two lenses already available internationally—the Veriflex and the AcrySof Cachet—are in U.S. clinical trials. Ophthalmic surgeons in Europe have several other lenses to choose from as well, which can provide hyperopic and toric as well as myopic correction.
Monika A. Landesz, MD, PhD, a cataract and refractive surgeon in the Hague area of the Netherlands, commented on the angle-supported, anterior chamber Cachet lens, which received the CE mark in 2008: “This lens shows promise in terms of safety and effectiveness but has only five years of long-term results compared with 20 years for the Artisan [Verisyse] lens, which is popular in the Netherlands.”
Diopters as Definers
For many ophthalmologists, the choice between pIOLs and corneal refractive procedures is based on the level of myopia. Jason E. Stahl, MD, who specializes in lens implant surgery and refractive surgery at Durrie Vision in Overland Park, Kan., and is assistant clinical professor of ophthalmology at University of Kansas in Kansas City, noted that pIOLs are a viable treatment alternative for individuals with moderate to high myopia who are not good candidates for corneal refractive procedures.
Dr. Stahl defines moderate myopia as between –3 and –6 D, and high myopia as greater than –6 D. However, he also describes a subcategory of patients with myopia between –6 and –8 D. “With moderate myopia, refractive surgeons are generally comfortable with a corneal procedure such as LASIK or PRK,” said Dr. Stahl. “And in my practice, most of the individuals in the –6 to –8 D range will also be good candidates for laser vision correction.”
Is –8 the limit for corneal procedures? “However, once you reach the level of –8 D or worse, you are getting into the territory where pIOLs outperform laser vision correction,” Dr. Stahl said. “There are several studies comparing pIOLs to lasers in patients in the –8 to –12 D range, and the pIOLs are superior in terms of best-corrected visual acuity and safety.1 Contrast sensitivity was also shown to improve over the preoperative state after Verisyse implantation.”2
The Visian ICL also compares favorably with LASIK in myopes up to –12 D, with the ICL offering better safety, efficacy, predictability and stability,3 said Dr. Stahl. He added that it also performed better than PRK in these aspects.
Consider the corneal thickness. When deciding between pIOLs and laser correction, Karl G. Stonecipher, MD, director of The Laser Center in Greensboro, N.C., defines high myopia as –7 D and above. He noted that, in patients with a thin cornea (less than 500 µm), an intraocular procedure such as pIOL is preferable to corneal refractive surgery. “However,” he said, “most surgeons feel comfortable performing PRK on a patient with a corneal thickness less than 500 µm, as long as the corneal topography and anatomy are normal.”
Devices make a difference in high myopia. If thin corneas are not an issue, Dr. Stonecipher may opt for laser correction for patients up to –12 D, and the decision is directly related to the actual device. “For me, the device matters,” Dr. Stonecipher said. “When comparing the Visx CustomVue (Abbott Medical Optics) and the WaveLight Allegretto Wave (Alcon) systems—and we use both in our office— the WaveLight can treat myopes up to –12 D with excellent results.”
Dr. Stonecipher attributes this to the device’s faster delivery of the treatment. “The 400-Hz model gives us results in seconds versus minutes, and that time influences the outcomes,” he said. “The 400-Hz model takes half of the time of its 200-Hz predecessor, allowing us to correct high myopia with better outcomes and accuracy.”
In a recently published study,4 Dr. Stonecipher and colleagues reported results comparing three- and six-month results of the Allegretto Wave 200 Hz and 400 Hz for the treatment of patients with –6 to –12 D of myopia and up to 3 D of cylinder. He found that both platforms were effective; but at six-month follow-up, refractive predictability and visual acuity were statistically superior in the 400-Hz group, with 92 percent of patients with –7 D to –11 D of myopia and up to 3 D of cylinder achieving 20/20 vision.
However, while Dr. Stonecipher feels comfortable with laser correction for high myopes, he also routinely uses pIOLs in patients whose anatomy, preferences or occupation dictate that option. For example, he pointed out a study conducted by the military that found better low-luminance contrast sensitivity and night vision after pIOL implantation than after LASIK.5
Although the degree of myopia is often the first issue that comes to mind in choosing between the corneal procedures and pIOLs, it is far from the only consideration.
Age. Dr. Stahl noted that age is an important factor. “To me, age 49 is the cutoff for pIOLs,” he said. “We know that higher myopes form cataracts at an earlier age, and I am worried that I will be taking out the pIOL to do a cataract procedure in a few years.”
Dr. Stonecipher’s age cutoff for pIOLs is 46 years and above, “but again, this is based on a number of individual factors.”
Adverse effects. Some physicians are reluctant to implant pIOLs because of the risk of adverse effects, which can include long-term endothelial loss. “This is why I stress to pIOL patients that they must avoid eye rubbing,” Dr. Stahl said. “I also suggest to fellow surgeons that they closely monitor their patients every year for possible endothelial cell loss.”
Amar Agarwal, MD, chairman and managing director of Dr. Agarwal’s group of 47 eye hospitals in India, noted that other reported complications of pIOLs include postoperative inflammation, anterior capsular opacities, angle-closure glaucoma and luxation of the implant.
Dr. Landesz added that the type of lens may make a difference. “In general, I am not in favor of angle-supported lenses,” she said. “Although the implantation technique of these lenses is much easier, I am still a bit skeptical about the endothelial cells loss, possible rotation and pupil ovalization.”
Weighing the risks. However, these risks of pIOLs should be balanced against the risks of corneal refractive procedures. For example, LASIK in high myopes can induce higher-order aberrations, which in turn decrease visual quality. Post-LASIK ectasia, keratoconus and post-PRK haze are also a concern, Dr. Stahl said.
“The advantages of pIOLs are that the cornea is not involved, which is also why they might be a very good option in the future for correcting high astigmatism in keratoconus patients,” said Dr. Landesz.
What About Hyperopia?
No pIOLs are approved in the United States for correction of hyperopia, although several models are available internationally. Nevertheless, Dr. Agarwal does not use pIOLs in hyperopes, as he considers the anterior chamber to be too shallow in many of these patients. “Instead, I prefer to do a refractive lens exchange, and the results are very gratifying.”
On the other hand, Dr. Landesz has a preference for pIOLs in hyperopic eyes, as the results with laser are “less satisfying.” In general, she chooses pIOLs for hyperopes +4 D and higher. If a patient with more than +4 D is not a good candidate for a pIOL, based on age or other factors, she favors refractive lens exchange, preferably with a multifocal IOL.
A Matter of Personal Preference
“When considering pIOLs and laser vision correction, each individual surgeon must develop a decision tree based on the patient’s age and anatomy, as well as personal preferences,” said Dr. Stonecipher. “This tree will change based on technology and comfort level.”
“Indeed,” he added, “adoption of technology is usually based on what the surgeon feels is safe in his or her hands at that moment in time. Some ophthalmologists prefer intraocular procedures, while others are more comfortable with extraocular procedures, regardless of the new technology available.” For example, pIOL procedures will seem very familiar to cataract surgeons.
Dr. Agarwal advised, “One should view each case independently and use the best tool for that particular patient. Some patients might require a cornea-based treatment, while others may benefit from a lens-based treatment. And some might need a combination of both techniques, as Dr. Roberto Zaldivar from Argentina first showed in his bioptics procedure.
“And finally,” Dr. Agarwal said, “we should remember that, with elective procedures, some patients might be better left alone without any treatment.”
1 Malecase, F. J. et al. Ophthalmology 2002;109(9):1622–1630.
2 Lombardo, A. J. et al. Ophthalmology 2005;112(2):278–285.
3 ICL in Treatment of Myopia Study Group. Ophthalmology 2004;111(9):1683–1692.
4 Stonecipher, K. G. et al. J Refract Surg 2010;26(10):S814–S818.
5 Parkhurst, G. D. Comparison of night vision and contrast sensitivity in patients undergoing implantable collamer lens implantation or LASIK. Presented at the Annual Meeting of the American Academy of Ophthalmology; Oct. 19, 2010; Chicago.
Dr. Agarwal is a consultant for Staar, Bausch + Lomb and Abbott Medical Optics. Drs. Landesz and Stahl have no financial disclosures. Dr. Stonecipher is a consultant or speaker for and/or has received travel expenses from Abbott Medical Optics, Alcon, Allergan, Bausch + Lomb, Endure Medical, Inspire, LensSx, Nidek and Oasis.
Avoiding Upside-Down ICLs
“Inadvertent upside-down ICL implantation is one of the rare complications that may occur in the early learning curve,” Dr. Agarwal said. “This can cause continuous contact between the IOL and the lens capsule, resulting in cataract and change in the refractive outcome.”
Dr. Agarwal noted that this complication is preventable with proper loading of the ICL. “The standard implantation technique described by Staar Surgical should be followed; alternatively, some surgeons use a plunger to facilitate movement of the ICL within the tunnel of the cartridge and to push the folded ICL to the tip,” he said. “With this newer loading technique, instead of being pushed, the ICL is pulled using a special forceps passed through the nozzle of the cartridge. This prevents the ICL coming out of the cartridge in an upside-down position. There are two small dots next to the optical zone and two holes on the footplates (distal right and proximal left), which indicate the anterior side of the ICL.”