This article is from April 2005 and may contain outdated material.
In this virtual roundtable, we asked five leading lens replacement surgeons about their current practices. Here they share insights on refractive lens exchange, multifocal and accommodative IOLs, bimanual microsurgery and products in the pipeline they look forward to using.
1. Are You Practicing Refractive Lens Exchange?
Mark Packer, MD: Refractive lens exchange represents a safe and efficacious modality for the correction of all types of refractive errors, not just presbyopia. Our goal as refractive surgeons has become crisp, clear and colorful naked vision at all distances under all conditions of luminance and glare, much like the vision enjoyed by young emmetropes. In large part because of the popularity of LASIK, refractive surgeons have focused on the cornea as the tissue of choice for refractive correction. Excimer laser ablations, with wavefront guidance or prolate optimization, can achieve excellent results.
However, while the corrected cornea remains stable, the human lens changes. All young candidates for refractive surgery must be advised that they will eventually succumb to presbyopia and the need for reading glasses. In a subtler but nevertheless significant change, lenticular spherical aberration reverses from negative to positive as we age and causes substantial loss of image quality. Therefore, any refractive correction of spherical aberration in the cornea will be overwhelmed by aging changes in the lens.
Most commonly, however, the reason to consider refractive lens exchange remains the physical and biological limits of LASIK. In younger patients, with intact accommodation, the insertion of a phakic refractive lens offers a compelling alternative. Beyond the age of 45, any refractive surgical modality that does not address presbyopia offers only half a loaf to the demanding Baby Boomers.
Douglas D. Koch, MD: I perform refractive lens exchange in some presbyopic hyperopes. Typical candidates meet one of these criteria: > 3 D of hyperopia, early cataract formation or age 55 and older.
Although many surgeons have embraced this approach for essentially all hyperopic presbyopes, I am enthusiastic about wavefront-guided LASIK. The results that we have had in the FDA-monitored clinical trial with the Visx laser have been outstanding. For this reason, pending FDA approval, I plan to use this modality to perform hyperopic PRK or LASIK in many hyperopic presbyopes. The advantage is that the quality of vision is excellent, and it will enable me to “buy time” as new and better IOL designs become available over the next several years.
I generally avoid refractive lens exchange in myopic patients. I believe that these patients are ideal candidates for phakic IOLs, which can tide them over until cataracts form. Typically, high myopes develop cataracts relatively early (in their 50s), so phakic IOLs are an excellent transition device for them.
Samuel Masket, MD: I do refractive lens exchange for hyperopic individuals who exceed the safe range for LASIK. That may vary with corneal curvature, but the primary factor is the degree of hyperopia. Typically, I do not perform hyperopic LASIK or PRK above 3.5 to 4 D. For those patients, clear lens replacement is a better option. The concern, of course, is presbyopia that is induced by the surgery. If the patient exceeds the presbyopic age, generally 45, the choice of monovision or both eyes corrected for distance with the use of reading glasses is up to the patient. Also, the patient may consider the Array Multifocal IOL (AMO). Earlier in life, monovision or multifocality are better options because of the induced presbyopia with monofocal lens implants. I rarely perform refractive lens exchanges for myopes because of the true proclivity for retinal detachment.
David F. Chang, MD: The most common indications for refractive lens exchange in my practice are either presbyopic myopes with early cataracts or presbyopic hyperopes. Presbyopic hyperopes are relatively good candidates for the Crystalens (Eyeonics) or a multifocal IOL, because they already have such poor UCVA. Their modest expectations for uncorrected near vision are usually met with these IOL technologies, as long as we achieve emmetropia.
Myopes in their 50s and 60s with early cataracts are relatively poor candidates for LASIK despite their professed interest. They will experience progressive lenticular myopia and will later face the problem of IOL calculation after keratorefractive surgery. For this group, lens replacement can achieve the same refractive result as LASIK without the other two associated problems. Of course, they must carefully consider the risk of pseudophakic retinal detachment. If their vitreous has previously detached and they are already developing a nuclear cataract, I believe refractive lens exchange is a reasonable option, assuming one uses an IOL with a truncated edge. The most common myopic refractive lens exchange patient has a cataract dense enough to warrant surgery in the first eye and an early cataract in the second eye and prefers to not wear a contact lens for the anisometropia created by the first surgery.
Randall J. Olson, MD: Refractive lens exchange has been a powerful tool for me, particularly for patients with early cataracts who are interested in refractive surgery. I think it is a mistake to do refractive surgery, which often affects biometry, in these patients. The quality of overall vision is better with refractive lens exchange, which does not induce corneal aberrations, and it is inevitable that cataract surgery would occur sometime in the future in these cases. This has been particularly effective for hyperopes, in whom the risk of retinal detachment is extremely small and refractive precision with LASIK is not nearly as good as it is with myopes.
2. Are You Using Multifocal IOLs? Which Ones, and Why?
Dr. Packer: I have used the Array Multifocal IOL extensively for both cataract and refractive lens surgery. While the Array offers excellent uncorrected distance and near uncorrected binocular acuity, patients must understand preoperatively the presence of halos around lights at night and the potential for dysphotopsia.
I have heard surgeons advocate telling patients whom they intend to implant with the Array, “You are not allowed to complain for three months.” This advice reflects their understanding of the phenomenon of neuroadaptation, which appears to diminish halos and lead to the return of pseudophakic contrast sensitivity. Our results with the Array indicate that virtually all patients can achieve a level of vision adequate for driving and reading without spectacles.
We look forward to gaining experience with the Restor IOL (Alcon) and beginning clinical investigation of the Tecnis Multifocal IOL (AMO), a prolate diffractive IOL. Optical bench studies indicate that the Tecnis IOL will offer a level of functional vision equivalent to a standard spherical monofocal IOL.
Dr. Chang: I continue to offer the Array IOL to select patients who have been carefully screened for proper pupil size (not too large), strong desire for spectacle independence and realistic expectations. Because of the Crystalens pricing, this is the only such option for Medicare patients with cataracts. I will be very interested in evaluating and comparing the Restor IOL to the currently approved devices.
Dr. Masket: I rarely employ multifocal IOLs. Although I had a positive and significant experience with the Array lens earlier, I have found that patients are no longer tolerant of the visual side effects associated with the Array lens. My sense is that patient expectations are unrealistic, and based somewhat upon the hyperbole and marketing associated with LASIK. Another possible explanation for my practice is a post-9/11 mentality: Patients seem less trusting and more sensitive. As a result, they expect and demand a higher quality of vision than is generally achieved in my experience with pseudoaccommodating IOLs.
Dr. Koch: I am not using multifocal IOLs. I have been disappointed by the quality of near and distance vision that some patients achieve with these. I am enthusiastic about upcoming designs, such as the Restor IOL. However, with all multifocal designs, I am concerned about quality of vision, particularly in aging patients who develop macular degeneration. My experience with earlier designs is that patients suffer a more precipitous drop in vision with any type of additional ocular pathology, such as posterior capsular opacification or, more ominously, AMD.
Dr. Olson: I have used a fair number of multifocal IOLs, but have had enough complaints about vision at night that I generally use them only for the perfect candidate who is committed to this technology. The presbyopic hyperope, for example, who is willing to put up with almost anything to avoid glasses is an excellent candidate, as are those who specifically request a multifocal lens.
The new Restor lens may have definite advantages in regard to night images. I have not used this lens yet, so my attitude about multifocal IOLs may change in the future.
3. Are You Using Accommodative IOLs?
Dr. Masket: Presently, the Crystalens is the only accommodating IOL on the U.S. market. The U.S. clinical investigators presented a great deal of enthusiasm for this product. However, in Europe, where the product is widely available, surgeons have not found the lens to perform up to expectations. Laboratory testing had not demonstrated a significant anterior movement of the lens as described by the manufacturer. It appears that the lens might be more pseudo- than truly accommodative. Additionally, the 4.5-millimeter optic has been associated with an increased degree of nighttime glare. In a study presented at the ESCRS meeting in September 2004, 20 percent of patients with that device had nighttime glare difficulties.
It is unlikely that my patients would be satisfied with the current design. My practice tends to include patients who often have unrealistic expectations of the outcomes of cataract and lens-related surgery. I am very cautious about having them pay a premium for a technology that may not deliver quality of vision commensurate with their expectations.
Dr. Olson: Although colleagues I trust do report good results with the Crystalens, studies from Europe suggest that the overall accommodative effect is too small to explain the results that supporters of this technology claim. This has been a paradox, trying to explain the marked diversity of support for this particular lens. At this point, I am reserving judgment. When clear evidence shows that an accommodative lens works well without significant optical side effects, this will be an important surgical modality that I will pursue.
Dr. Packer: We served as investigators for the Crystalens. The data from that study indicate that 73 percent of patients implanted bilaterally wear glasses rarely or not at all. The majority can read most things and use the computer without glasses. However, only a minority is able to do close work, such as sewing, without correction. The Crystalens does not guarantee spectacle independence, but it does offer a significant improvement over monofocal vision for those patients who value spectacle independence. In addition, the Crystalens provides contrast sensitivity equivalent to a monofocal lens with less risk of dysphotopsia than with a multifocal optic.
Dr. Koch: I am strongly considering using the Crystalens in very carefully selected patients, but I would like to see a larger optic and ultraviolet filtration up to at least 400 nanometers (vs. the current 350 nm), and I share the concerns about uncertain mechanism of action. Other yet-to-be approved designs of accommodative IOLs are intriguing but have hurdles to clear before they can become available clinically.
Dr. Chang: When discussing the Crystalens, I try to undersell and underpromise. As we learned with the Array Multifocal IOL, the surgeon should not “push” the technology, and patient expectations must be realistic. Most of my Crystalens patients have been hyperopes, because movement of a higher-power IOL will provide a greater refractive shift compared with lower dioptic powers, and the patients are easier to satisfy. Of course, how this IOL design increases near function is controversial, with the theory of Jack Holladay, MD, being that the smaller optic, like a camera’s smaller “f” stop, increases depth of field. While my carefully selected patients have been quite happy, I have been impressed that a fair number don’t read very well through their best distance correction. I think that a conservative approach continues to be warranted.
4. Are You Performing Bimanual Microsurgery in Your Cataract Patients?
Dr. Koch: I perform bimanual microsurgery in selected cataract patients. I believe it is a technique that is still evolving and that, with current instrumentation and techniques, provides no apparent advantages over routine phacoemulsification. The primary deficiency of this technique is the reduced infusion provided by the second instrument. This necessitates a reduction in flow and vacuum settings in order to preserve chamber stability.
Nevertheless, bimanual microphaco does improve the maneuverability of the phaco tip, and it is uniquely advantageous in patients who have undergone multiple-incision RK, since the cataract incisions can be placed between the narrowly spaced RK incisions. When we have improved fluidics and a high-quality IOL that can be inserted through a sub-2-mm incision, bimanual microphaco will become the standard.
Dr. Chang: During the past few years, bimanual microphaco has rapidly evolved into a viable and reproducible procedure. Despite my early and strong interest in learning this technique, I still find standard coaxial phaco to be faster and more forgiving. However, like comparing bimanual irrigation and aspiration to coaxial I&A, there are some situations where I believe bimanual microphaco is advantageous. Examples would include zonular dialysis cases and eyes with extremely weak zonules that may be overly stressed by too strong an infusion force. Surgeons who are proficient at phaco chop will find the transition to bimanual microphaco much easier.
Dr. Olson: I started doing bimanual microphaco more than five years ago and have found it a very interesting approach. In my experience, it has been superior for some patients, particularly when there is a problem with pressurizing the anterior chamber, such as with an intumescent cataract during capsulorhexis, or when the anterior chamber is extremely shallow and iris prolapse is likely. This includes some cases of pseudoexfoliation syndrome, phacomorphic glaucoma and nanophthalmos.
For the average patient, while microphaco is effective and safe, I am not sure that there is an advantage over coaxial phaco as long as we have to use a large-incision IOL. I think good small-incision IOLs (sub-2-mm), when they become available, will dramatically change this mind-set for me and for others. I will continue doing bimanual microphaco in the many cases where it has a clear advantage.
Dr. Packer: I use bimanual micophaco in 100 percent of my surgery. I began using it in anticipation of microincisional IOL clinical trials, but soon discovered advantages that make microphaco a superior procedure entirely on its own merits. These include enhanced chamber stability, improved fluidics and followability, the addition of the irrigating stream as a new tool within the eye and the ability to switch hands with the instruments, therefore eliminating the problematic subincisional area. The development of new instrumentation—including microincision diamond knives, precise capsulorhexis forceps and innovative irrigating choppers—has made the adventure of bimanual surgery a real pleasure. State-of-the-art phaco machines are capable of power modulations and fluidics management that permit exceptional chamber stability as well as efficient chopping, mobilization and extraction of lens material with minimal use of ultrasound energy. These developments permit incredibly rapid visual rehabilitation for patients who are coming to expect refractive surgery-like results after cataract surgery.
5. What Future IOLs or Techniques Are You Looking Forward to Using?
Dr. Packer: New IOLs are on the horizon that will continue to push cataract surgery closer to refractive surgery. Dual-optic accommodative IOLs offer greater amplitude of accommodation, while a thermoplastic acrylic IOL may enable accommodation with a full-size lens that can be inserted through a 1.5-mm incision. Microincision lenses are already available outside the United States, and research continues in injectable polymer lens material. The Light Adjustable Lens (Calhoun Vision) offers the exciting possibility of refractive correction postoperatively, after the IOL is in a stable configuration in the eye.
Dr. Masket: The hope for and the wave of the future will be accommodating IOLs. Much work needs to be done in this arena. The IOL industry must find an answer for the postoperative reactions of the lens epithelial cells [LECs]. In particular, fibrometaplasia of the LECs leads to opacification and inflexibility of the capsule bag. Therefore, in addition to finding truly accommodating lenses, we must maintain flexibility and clarity of the lens capsule. I estimate that by the end of the decade, we should have a far better set of lenses and expectation for our patients. Hopefully, we can expect adjustable and fully accommodating IOLs that will not induce or may even correct for higher-order optical aberrations. In the very near term, I look toward the Restor IOL as a possibly improved pseudoaccommodating IOL.
Dr. Koch: I look forward to several advances, including the Calhoun IOL for modifying not only sphere and cylinder but also higher-order aberrations and, more immediately, the toric Acrysof IOL (Alcon). I participated in the clinical trial and was tremendously impressed with the stability of the Alcon toric lens and the quality of the visual results. Although I have devoted many years to refining incisional approaches to reducing astigmatism during cataract surgery, I plan to abandon astigmatic keratotomy in lieu of this toric lens whenever the astigmatism can be corrected by available lens models.
In addition, I look forward to further evolution of the Aqualase technology (Alcon) for removing soft and medium cataracts. This modality has tremendous promise, and with further refinements, it could become the preferred approach for many standard cataracts. As Stephen Lane, MD, has demonstrated, it may also become a preferred modality for bimanual microphaco.
I look forward to the release of the Restor IOL and advances in accommodating IOLs, of which there are several promising candidates, and to advances in IOL designs for treating patients with AMD.
Dr. Chang: The toric Acrysof IOL will be a welcome option, because this combination of IOL design and material should be less likely to rotate than its plate-haptic silicone predecessor. A modified prolate multifocal (such as the Tecnis IOL) may be the best way to minimize the contrast loss otherwise inherent to multifocal optics. As far as an accommodating IOL, a dual-optic design such as the Visiogen Synchrony should theoretically produce a much greater refractive shift than a single-optic moving design.
Finally, the laser-adjustable Calhoun IOL offers exciting prospects, ranging from postoperative spherical and astigmatic correction to a customized multifocal with guaranteed emmetropia. The ultimate application would be to perform custom wavefront correction on a stable pseudophakic platform. Cataract patients sometimes ask me whether their surgery can be redone if a better IOL technology arrives in the future. Well, imagine piggybacking a Calhoun IOL into a pseudophake’s sulcus, and then adjusting that eye to emmetropia with a custom wavefront-corrected multifocal pattern.
Finally, I am a clinical investigator for the Ophtec artificial iris implant and the Vision Care Implantable Miniature Telescope. Both technologies will benefit patient populations that currently lack good alternatives.
Dr. Olson: As most of my surgery is refractive in design, I find the Calhoun light-adjustable IOL to be powerful technology. In the future, it should provide refractive precision for cylinder and sphere as well as for higher-order aberrations that is simply impossible to equal with corneal surgery. I also am excited about several new technologies that will produce a much better accommodative effect for my presbyopic patients. A combination of both, obviously, will add tremendous value for cataract patients and for those receiving refractive lens exchange in the future.
Meet the Experts
David F. Chang, MD Clinical professor of ophthalmology at the University of California, San Francisco, and in private practice in Los Altos, Calif. Financial interests: Is a consultant to AMO, consultant and U.S. medical monitor for Visiogen and has received educational travel support from Alcon, but has no financial interest in any instruments or devices mentioned.
Douglas D. Koch, MD Professor of ophthalmology at Baylor College, Houston. Financial interests: Is a consultant to Bausch & Lomb, Alcon and Pharmacia.
Samuel Masket, MD Clinical professor of ophthalmology at the University of California, Los Angeles, and in private practice in Century City, Calif. Financial interests: Is a consultant to AMO, a member of the Alcon speakers’ alliance and medical director of Medennium, which has a sub-2-mm IOL on the drawing board.
Randall J. Olson, MD Professor and chairman of ophthalmology at the University of Utah, Salt Lake City.Financial interests: Is a consultant for AMO and head of the medical advisory board for Calhoun Vision.
Mark Packer, MD Clinical assistant professor of ophthalmology at Oregon Health & Science University and in private practice in Eugene, Ore. Financial interests: Receives travel and research support from Alcon and AMO.