Premium IOLs to correct presbyopia have become a growing area of interest for optometrists, with an increasing number of offerings on the U.S. market.
These lenses are not only used for cataract correction, however. Patients have increasingly showed a willingness to spend out of pocket to have a premium IOL implanted in refractive lens exchange if it offers less spectacle dependence. Because patients are seeking a refractive fix, even in cases that involve a cataract, they are expecting refractive results.
Robert E. Prouty
According to most published studies, the ReZoom (AMO, Santa Ana, Calif.) and AcrySof ReStor (Alcon, Fort Worth, Texas) multifocal lenses offer patients good close and distance vision. A third lens choice, the Crystalens 5.0 (Bausch & Lomb, Aliso Viejo, Calif.), which was recently complemented on the market by the introduction of the Crystalens HD, is designed to restore some of the eye’s natural accommodative ability lost to presbyopia and appears to provide good vision across near, intermediate and distance.
“There is no perfect IOL, period,” Robert E. Prouty, OD, FAAO, center director at Omni Eye Surgery in Denver, told Primary Care Optometry News in an interview. “When we’re looking at these lens types, we have to choose the right lens with the best technology for a particular patient’s needs.”
Multifocal vs. aspheric
The lens choice for a particular patient will depend first on ocular health but also on what the patient hopes to gain in his or her vision.
“As long as a patient has no ocular pathology, which means no glaucoma, macular degeneration, retinal problems or corneal scarring that could affect their overall result with either Crystalens, ReZoom or ReStor, then we go into a discussion about those lenses being a potential option,” Todd Agnew, OD, director of clinical services at Key Whitman Eye Center in Dallas, told PCON.
If money were not an issue, Dr. Agnew added, most patients would select a presbyopia-correcting IOL. Monofocal optics, either spheric or aspheric, are a consideration when the optical system is compromised, when the price is a hindrance or when the resulting vision will not allow the patient to accomplish what he or she desires.
According to Katherine Mastrota, OD, MS, FAAO center director of Omni Eye Surgery in New York, “Multifocals do, on some level, split light and reduce contrast sensitivity, and if you’re trying to work with an optical system that is challenged to begin with – be it retinal, corneal, optic nerve – these patients may not fully appreciate the specialized optics of a multifocal IOL. We aim to put in the best monofocal we can. If that’s an aspheric, that’s where we’ll go.”
The natural architecture of the eye may help explain why aspheric lenses are desirable. In the phakic eye, the positive spherical aberration of the prolate cornea is compensated for by the negative spherical aberration of the human crystalline lens. According to Dr. Prouty, spherical IOLs affect contrast sensitivity and diminish quality of vision while restoring quantity of vision.
“Spherical aberration was an issue [with early spheric IOL designs], but now we can compensate for that,” Dr. Prouty said.
Visual needs, lens selection
Of the three premium IOLs mentioned, Crystalens is the only monofocal option. This might be an important consideration for patients who drive at night, for instance, or who may not be able to adapt to the compromises of multifocal lenses.
“The way the multifocal lenses are designed, they reduce light focus to the back surface of the eye,” Dr. Agnew said. “You’ll have less light degradation with a monofocal lens.”
However, Dr. Prouty points out, the ReStor lens might be better suited for patients who may not use intermediate vision as much. “The benefit of this lens is that you have excellent vision at distance and excellent vision at near,” he said. “The intermediate is good; it’s not as good as near-near or far-far, but it’s still good. The downside of the current lens is that the reading portion is a little closer than is normally comfortable.”
Patients may want to consider the functional range of vision and the usefulness of the resulting vision. For instance, a patient who does needlepoint may want closer near vision than a patient who reads magazines on a consistent basis.
“New focal range for patients is within 36 inches from the face,” Dr. Agnew said. “Even though the ReStor is still the best at 12 to 14 inches, Crystalens gives the most range of focus with the least distortion, glare or halo compared to the other two.”
On the other hand, patients who need to use intermediate vision more frequently might be more suited to the ReZoom. “ReZoom is a good choice for younger patients in the work force who require more flexible range of vision. These individuals have different day-to-day demands than seniors,” Dr. Mastrota said in an interview. “Low myopes and hyperopes with low amounts of corneal cylinder do the best.”
Although they diminish with time, the glare and halo that can occur in multifocal lenses may limit their acceptance in patients needing consistently functional distance vision. “If your patient does a significant amount of night-time driving, you may want to consider another lens,” Dr. Mastrota said.
To address patients’ desired range of vision, clinicians may choose to use a multifocal in one eye and an accommodative lens in the other. Some critics of the strategy have argued that pairing inhibits neural adaptation, while proponents see it as complementing inherent compromises with inherent advantages of the paired lens.
Another strategy used to create a deeper range of functional vision with the Crystalens is pseudophakic monovision, or intentionally defocusing the nondominant implant to slight myopia. By doing so, some contrast sensitivity and binocularity are sacrificed by pushing the near vision back slightly, and the resulting vision is theoretically deeper and more complete once neuroadaptation is accomplished.
However, the need to pursue that strategy might be negated with the release of the new Crystalens HD, according to Dr. Agnew.
“If I had to choose the biggest difference in going from the Crystalens 5.0 to the HD that has helped the patient it is this: with the 5.0 most surgeons would aim for about 0.75 D to 1.00 D of myopia in the nondominant eye, whereas now we are getting closer to spherical zero,” Dr. Agnew said.
“Every patient needs to be advised that this technology is available, whether or not you think he or she is a candidate,” Dr. Mastrota said. “Then, the patient needs to consider the options and your recommendations to make an informed decision.”
According to Dr. Mastrota, striving for good informed consent will improve the patient’s satisfaction with their IOL choice. “If the patient is counseled and screened appropriately, and if you really understand what they are looking to accomplish, they do well,” she said.
“Patients have to adapt to multifocal and accommodative IOLs,” Dr. Mastrota continued. “In the first post-operative week they may need encouragement adapting to their ‘new’ visual system, but as everything starts to come together and the distance and near vision improves, they are pleased.”
According to Dr. Prouty, “We’re guiding patients through the available lens options to assist them in setting up their visual performance for the rest of their life. So it really is refractive surgery, just as if it were LASIK.”
For more information:
- Robert E. Prouty, OD, FAAO, can be reached at Omni Eye Specialists, 55 Madison St., Ste. 355, Denver, CO 80206; (303) 377-2020; fax: (303) 377-2022; e-mail: RProuty@DrMyii.com. Dr. Prouty has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
- Todd Agnew, OD, can be reached at 2801 Lemmon Ave Ste 400, Dallas, TX 75204; (214) 220-3937; email: Agnew@keywhitman.com. Dr. Agnew is a paid consultant for Bausch & Lomb.
- Katherine Mastrota, OD, MS, FAAO, can be reached at Omni Eye Surgery, 36 East 36th Street, New York, NY 10016; (212) 353-0030; fax: (212) 353-0083; e-mail: KatherineMastrota@msn.com. Dr. Mastrota is a paid consultant for AMO.