On behalf of ISRS/AAO and the Turkish Cataract and Refractive Division of the Turkish Ophthalmological Society, thank you for attending the 2006 ISRS/AAO Meeting, International Refractive Surgery: Art and Science in Istanbul, Turkey. It was an enormous success in a spectacular city, with 539 registrants and 34 faculty from around the world. We have summarized a couple of the presentations picked as the Best of Session papers. The next ISRS/AAO meeting planned for Las Vegas, Refractive Surgery 2006: The Times They Are A-Changin', is fast approaching. Registration is now open for Academy Members and will open July 12 for nonmembers. -- Marguerite B. McDonald, MD, FACS
- Is a truly accommodating lens possible? Are multifocal IOLs good enough?
- Wavefront-guided surface ablation with MMC may decrease ocular aberration and increase visual acuity after LASIK flap complications
- Understanding molecular biology is the key to better corneal wound healing
- Wavefront-supported PRK can produce good outcomes in patients with suspected keratoconus and thin, irregular corneas
- Topical aproclonidine may have positive effect for LASIK patients
- Good outcomes with intacs for keratoconus depends on low mean K values and low spherical equivalent
- Better outcomes with single-segment intacs for keratoconus and post-LASIK ectasia compared to double-segment intacs
- Adverse reactions from cataract surgery combined with ICL removal and IOL implantation appear minimal
- Two-year results for conductive keratoplasty for hyperopic astigmatism appear promising
- Pascal dynamic contour tonometer may be better suited for monitoring IOP in post LASIK eyes
- Congratulations to the Best Paper of the Session award winners of the 2006 ISRS/AAO Istanbul meeting
- Registration and housing for 2006 Joint Meeting and Subspecialty Day is now open
- Have you paid your ISRS/AAO dues yet?
- Academy reaches out to the world with International Center
Is a truly accommodating lens possible? Are multifocal IOLs good enough?
Samuel Masket, MD, clinical professor of ophthalmology at the Jules Stein Eye Institute in Los Angeles, Calif. and president of the American Society of Cataract and Refractive Surgery, considers these questions in this month’s feature article.
Wavefront-guided surface ablation with MMC may decrease ocular aberration and increase visual acuity after LASIK flap complications
In a paper presented at the 2006 ISRS/AAO meeting last month, Akif Ozdamar, MD, discussed LASIK complications such as button hole, free flap, thin flap, short flap or a torn flap. In these cases, the first option may be to create another flap, but the complication rate is higher for a secondary flap (12.5 percent) and outcomes will be limited by corneal scar and irregularity as well as an increased risk of decreased BSCVA. Dr. Ozdamar has achieved good outcomes using surface ablation with adjunctive use of MMC 0.2 mg/ml to prevent visually significant corneal haze. He concludes that it’s a promising alternative for the treatment of LASIK flap complications in patients with decreased BSCVA. But nomogram adjustment is needed for improving refractive accuracy.
Understanding molecular biology is the key to better corneal wound healing
In a paper presented at the 2006 ISRS/AAO meeting last month, Murat Irkec, MD, described how cell to cell interactions make critical contributions to development, homeostasis and wound healing in the cornea. Many of these cell to cell interactions are mediated by cytokines, growth factors and chemokines. Therefore, a molecular biological approach would help optimize corneal would healing, help preserve the optical quality of the cornea in refractive surgery and modulate pathological processes and improve surgical outcome.
Wavefront-supported PRK can produce good outcomes in patients with suspected keratoconus and thin, irregular corneas
Twenty patients (40 eyes) were followed for forty months after treatment for myopia and myopic astigmatism. Mean uncorrected visual acuity improved from 20/400 to 20/25. Treatment also led to a more regular corneal surface with significant flattening of inferior corneal steepness. Journal of Refractive Surgery, June 2006
Topical aproclonidine may have positive effect for LASIK patients
Applied before surgery, it may prevent immediate postoperative hyperemia and prolonged subconjunctival hemorrhage via its alpha-mimetic vasoconstrictor effect. No flap adherence complications occurred in this randomized, controlled study of 66 patients. Journal of Refractive Surgery, June 2006
Good outcomes with Intacs for keratoconus depends on low mean K values and low spherical equivalent
Visual results were compared in 25 eyes six months after implantation surgery to evaluate factors influencing outcomes. In eyes with relatively low mean K values (=53 D) and a relatively low spherical equivalent, Intacs provided better results in visual acuity and corneal topography quality and significantly reduced the spherical equivalent. Poor results were strongly associated with patients with advanced keratoconus (mean K-reading =55 D). Journal of Cataract & Refractive Surgery, May 2006
Better outcomes with single-segment Intacs for keratoconus and post-LASIK ectasia compared to double-segment Intacs
This retrospective analysis compared results from 11 patients (17 eyes) who received single-segment Intacs with 17 patients (20 eyes) who received double-segment intacs. UCVA improved more in the single-segment group (nine lines) than in the double-segment group (2.5 lines). BSCVA improved more in the single-segment group (2.5 lines) than in the double-segment group (less than one line).Corneal asymmetry was also more improved in the single-segment group, and the cylinder decrease was greater. The authors conclude that better visual results are due to the inferior flattening and superior steepening induced by single-segment Intacs. American Journal of Ophthalmology, May 2006
Adverse reactions from cataract surgery combined with ICL removal and IOL implantation appear minimal
This retrospective case series evaluated 12 patients (14 eyes) with implantable contact lenses (ICL) who developed a cataract. Six months after simultaneous ICL removal and cataract extraction with pseudophakic IOL implantation, 10 eyes were within ±1.0 D of the calculated target and no patient lost BCVA. No major adverse events were observed. One eye had a tear in the posterior capsule with vitreous loss during cataract surgery. The authors conclude that careful preoperative evaluation and proper ICL length selection is required to decrease the incidence of cataract. Journal of Cataract & Refractive Surgery, April 2006
Two-year results for conductive keratoplasty for hyperopic astigmatism appear promising
This non-randomized, non-controlled study of 47 eyes treated for low hyperopic astigmatism finds uncorrected visual acuity was 20/20 or better in 37 percent of eyes and 20/40 or better in 97 percent. No eye lost two or more Snellen lines or had an induced cylinder of more than 1.50 D. Journal of Cataract & Refractive Surgery, May 2006
Pascal dynamic contour tonometer may be better suited for monitoring IOP in post LASIK eyes
IOP was measured in 118 eyes before and after LASIK surgery using the Pascal tonometer (an improved version of the SmartLens tonometer with a tip with a concave contact surface that matches the contour of the cornea), Goldmann applanation tonometry (GAT) and noncontact air tonometry (NCT). The observed post-LASIK changes in GAT and NCT IOP measurements were not directly proportional to the change in CCT, refractive error or mean keratometric readings. The Pascal tonometer was not significantly affected by changes in corneal thickness, curvature, rigidity or morphology. The authors believe this is probably due to its ability to measure IOP transcorneally, without the need to applanate the corneal surface as much as the other instruments. Journal of Cataract & Refractive Surgery, April 2006
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Congratulations to the Best Paper of the Session award winners of the 2006 ISRS/AAO Istanbul meeting
They are: Jorge L Alio, MD, PhD, Correcting Corneal Irregularity Following Refractive Surgery; Uzeyir Gonenc, MD, Multifocal IOLs; Helen K Wu, MD, Pellucid Marginal Degeneration and Refractive Surgery; Murat Irkec, MD, Corneal Wound Healing: A Molecular Biological Approach; Alaa M El-Danasoury, MD, Clinical Results With Advanced Nidek Ablation Profiles; Akif Ozdamar, MD, Wavefront-Guided Surface Ablation with Prophylactic use of Mitomycin C in LASIK Flap Complications; Jack T Holladay, MD, MSEE, FACS, Optical Performance in the Human Eye of Spherical/Aspheric IOLs and Omer Faruk Yilmaz, MD, Acufocus.
Registration and housing for 2006 Joint Meeting and Subspecialty Day is now open
Academy Members and AAOE members can now register to secure their hotel of choice and course tickets. Registration opens to nonmembers on July 12.
Have you paid your ISRS/AAO dues yet?
To continue receiving member benefits, including this monthly newsletter, Refractive Surgery Outlook, please pay your dues now. For your convenience, you can pay online.
Academy reaches out to the world with International Center
We have created a place on our Web site to feature information and resources from the Academy that are of special interest to ophthalmologists from outside the United States. If you have suggestions for making this page more useful to international visitors, contact the Academy, email@example.com.
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Today’s Multifocal IOLs: Are They End or the Beginning of Refractive IOL Development?
Samuel Masket, MD
Let us begin by defining some terms. When we consider multifocal surgical options today we are talking about either an intraocular device (lens based surgery) or a corneal procedure that divides and bends light such that each eye can have simultaneous in-focus images from both distance and near. This is most frequently accomplished with intraocular lens (IOL) implants, but it can also be achieved by multifocal ablation.
Corneal inlays, by enhancing the depth of field in one eye, can help patients see at both distance and near. Conductive keratoplasty gives the patient good vision at distance and near, but, like corneal inlays, achieves its effect primarily via monovision. Monovision differs from multifocality in that with monovision only one eye has good near vision, while the other eye has good distance vision. With multifocality, both eyes have good distance and near vision, but with varying degrees of vision compromise
Today, the great majority of patients who have multifocal surgical correction receive IOLs, either in combination with cataract surgery or as a correction for presbyopia (clear lens replacement). Are these lenses the last word in refractive IOLs? There are two FDA-approved devices in widespread use in the United States today. One is the AcrySof® ReSTOR® multifocal IOL (Alcon), and the other is the AMO ReZoom® lens, which has largely eclipsed its predecessor, the AMO Array® multifocal IOL.
I am most familiar with the ReSTOR lens. FDA clinical trial results (which match what I see in my own patients) have shown it to have a very high success rate: more than 80% of binocularly implanted patients claim to never need spectacles, and 94% would have the lens again. The Tecnis® multifocal, from AMO, is a diffractive IOL. (By contrast, the ReZoom employs refractive optics only, and ReSTOR uses both diffractive and refractive optics.) Although the Tecnis multifocal is not yet available in the United States, the data from its European studies appears promising.
To achieve their optical ends, all multifocal lenses partition light, and, as a result, they reduce contrast sensitivity. While this loss is rarely clinically meaningful in healthy eyes, patients who have vision-limiting comorbidities, such as age-related macular degeneration or corneal scarring, may not be ideal candidates for these devices. Another drawback is that the multifocal design can produce undesired optical side effects (glare halos, etc). The net effect is that some patients, about 5%, will experience significant halos and glare at tnight with the ReSTOR IOL.
Although the number of dissatisfied patients is small, one cannot determine prior to surgery which patients will experience nighttime difficulty. My overall judgment is that these lenses can work quite well, but they have some limitations, the most important being that a small number of patients will be dissatisfied, but they cannot be identified prior to surgery.
An Inherent Limitation?
Are Multifocal IOL problems remediable? My sense is that multifocal technology cannot escape the issue of divided light and the limitations that entails. Many of the negative optical effects have been obviated by the apodized diffractive portion of the ReSTOR Multifocal. However, despite decades of work inspired by a massive potential market, the contact lens industry has been unable to produce a highly successful multifocal contact lens design. And multifocal excimer laser photoablation, has encountered limitations as well.
That said, most patients are extremely satisfied with multifocal lenses—I am delighted by how well my ReSTOR patients do. The technology is certainly good enough for the great majority of patients who choose it today. But I am equally certain that I would like to see the technology move forward, and I doubt that incremental improvements in multifocal lenses are possible or will get us where we need to be.
In the United States, we have one FDA-approved “accommodating” design, the crystalens® (eyeonics). Although it does provide patients with a greater range of vision than a monofocal lens, most of those who have studied it carefully agree that the crystalens doesn’t truly accommodate. Instead, the extended depth of focus it provides is likely achieved by its posterior positioning and small optic size; the latter provides increased focus depth by means of spherical aberration.
There are a host of accommodating lenses in the “pipeline” or under investigation. These are dynamic lenses, i.e., lenses that change either their shape or their position inside the eye to achieve a true change of power. Because accommodation requires this dynamic quality, achieving it will require that we also control or modulate the fate of the lens capsule after surgery.
Particularly important is the activity of the subcapsular lens epithelial cells following surgery. To succeed with accommodation, we must find a way to maintain flexibility and prevent opacification of the capsule by controlling the tendency for capsular fibrosis. This goal is being pursued in a number of ways.
Dynamism Is Key
Adequate accommodation requires either a flexible material or a multi-lens system within the capsular bag—we have learned from the crystalens and similar designs that a single lens system can’t move enough to provide adequate power change.
While multifocal IOLs should provide a good near-term solution, the real goal is a flexible IOL material that can be placed in the capsular bag (from which the original natural lens has been removed) and, like a natural lens, change shape in response to pressures from the ciliary muscles and vitreous body. This sort of device could produce a “natural” accommodation and also correct preoperative refractive errors, including higher order aberrations.
Truly accommodating lenses are still a way off, and making them a reality will likely require a combination of technologies. For example, one approach to fine tuning the optical outcomes of surgery is the Light Adjustable Lens a multifocal IOL from Calhoun Vision, which is developing a light-adjustable IOL; IOL power can be modulated following surgery.
Using this approach would allow fine tuning, so that both small errors in biometry and the variability inherent in a manual surgical technique could be corrected. Even residual higher order aberration could theoretically be minimized or eliminated. One of the most attractive features of an adjustable lens is the ability to let the patient “test drive” multifocality. For patients who didn’t like it, a return to monofocality would be possible.
Another product, the “smart IOL” (Medennium) uses a hydrophobic acrylic material to fill the capsular bag. The material is solid at room temperature but flexible at body temperature and so capable of accommodation. Because the material has “memory,” it can be preshaped to provide correction of preexisting refractive error. Theoretically, if the Medennium or a similar product can be made to work, it might be combined with the Calhoun Vision technology to gain adjustability as well.
However, before any in-the-bag gel solution can be realized, a large number of problems have to be solved, including maintenance of capsular flexibility and prevention of opacification.
Closer in the Pipeline
In the interim, other technologies are being explored. One of them, the Synchrony IOL (Visiogen) is a dual-optic lens that acts like an intraocular telescope. The Synchrony’s two lenses move with respect to each other to change power. During accommodation the separation between the lenses increases, adding dioptric power to the system and bringing near objects into focus for the patient.
The Synchrony lens seems to be doing well in clinical trials, but whether it will achieve enough dioptric change to satisfy patients’ needs and whether the lens capsule bed will remain adequately flexible over a long period of time remain to be seen. Current U.S. investigational trials will continue for approximately 3 more years.
It is reasonable to believe that the market for an IOL that permits “seamless” clear vision at all distances is huge and lucrative, so significant resources are being poured into the effort to resolve the problems of accommodating IOLs. I believe that within the next five years we will see several new partially accommodative lenses join the crystalens on the market. I also think that new technologies will become available to modulate the postoperative reaction in the lens’s epithelial cells.
Five years, however, is too little time to develop a commercial in-the-bag flexible polymer that mimics the crystalline lens. Ten years is a more likely threshold for polymers that accommodate adequately, and, perhaps, are even adjustable so that we can achieve the desired optical result. Ten years may be overly optimistic, but I believe that there is a chance that we will see such IOLs by then.
Where Are We Today?
Will there come a time when we have a surgical option to offer early presbyopes with clear lenses? Absolutely. Are we there today? Not quite. While I use multifocal IOLs for clear lens replacement in patients who are significantly hyperopic, I remain skeptical of using them in myopes with clear lenses because of the risk of retinal detachment. That said, I think the technology is good for the overwhelming majority of cataract patients who want greater spectacle independence.
I believe enough in multifocal technology to have implanted my sister with the ReSTOR lens, and she has done extraordinarily well, as have the great majority of my multifocal IOL patients. But as good as multifocal IOL technology has become, I would not be comfortable offering it to a 50-year-old emmetrope solely as a replacement for his reading glasses. I believe we will get to that point, but we are not there yet.
Please Check Carefully: THANK YOU!
Samuel Masket, MD, is in private practice in Los Angeles and clinical professor of ophthalmology at the Jules Stein Eye Institute, UCLA Center for Health Sciences, Los Angeles, CA, USA. He is currently president of the American Society of Cataract and Refractive Surgery. Dr. Masket is a consultant to Alcon and Visiogen.
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