 | | Clinical News Live from the 4th Annual Regional Meeting of the International Society of Refractive Surgery of the American Academy of Ophthalmology (ISRS/AAO) in Cancun, Mexico
SATURDAY, MAY 31, 2008 |
Editor-in-Chief: H.Dunbar Hoskins Jr., MD | Managing Editor: Susanne Medeiros
Advisory Panel: Andrew Iwach, MD, Terry L. Forrest, MD, Jean E. Ramsey, MD,
Franco M. Recchia, MD, James C. Tsai, MD and Helen K. Wu, MD
Thank You ISRS/AAO President Marguerite B. McDonald, MD and Program Directors Ramon Naranjo-Tackman, MD, José Manuel Vargas, MD, and Steven E. Wilson, MD, would like to thank Alcon for their generous contribution to the 2008 Cancún Meeting.
Study finds EpiLASIK may produce fewer aberrations than PRK and LASIK Crisanti Stangogiannis-Druya, MD, of Venezuela, today presented some surprising results from a prospective study comparing three years of aberrometric findings following customized EpiLASIK, PRK and LASIK. “I don’t mean to say that the other techniques don’t work. Every patient is a different case. But we did find that Epi-LASIK does induce fewer aberrations, with less spherical aberration and coma. The difference was statistically significant,” Dr. Stangogianns said. Why? It’s unclear, but she has a theory: “It spares the epithelium. It’s not such a deep cut and doesn’t change the biomechanics of the cornea. Based only on the aberration and postoperative behavior, we believe that epiLASIK seems a reasonable alternative for wavefront-based treatments.” In her study, all surgeries were done based on Visx WaveScan measurements using the Visx S4 excimer laser. The LASIK group included 16 eyes; EpiLASIK, 15; PRK, 10. The central 6 mm of each eye were analyzed with Wavescan and LadarWave before surgery and at one, two and three years postop, with and without cycloplegia in every case.
In a separate presentation, Carlos Verges, MD, of Spain, discussed his non-randomized comparison of EpiLASIK with PRK and thin flap LASIK. At six months postop, the LASIK group reported the highest induction of aberrations, RMS 0.25. He also showed that at six months postop LASIK eyes showed a 48 percent reduction in corneal biomechanics, while eyes treated with surface ablation showed a reduction between 10 percent and 14 percent. In addition, he found that patient satisfaction was higher with Epi-LASIK compared to PRK because visual recovery was faster and they felt less discomfort. Dr. Verges said that it's results like this that have prompted him to perform more surface ablation treatments. “Right now more than 50 percent of my patients are surface ablation. I urge you to think about this choice.” Dr. Verges has financial interests with AMO, IoLTECH Laboratories, Moria and WaveLight. Back to Top
Biomechanical customization may better screen for ectasia and its susceptibility Renato Ambrosio Jr., MD, today encouraged physicians to go beyond the classic corneal topography and pachymetry measurements and begin including corneal tomography and biomechanical measurements when screening patients for ectasia. This customized data significantly increases sensitivity and specificity, allowing the physician to not only detect ectasia but also ectasia susceptibility, Dr. Ambrosio said. Corneal tomography (CTm) is obtained by using the rotating Scheimpflug camera to calculate a cornea thickness spatial profile, progression of increase of thickness and the average progression index. Elevation maps for anterior and posterior corneal surfaces were calculated using a new reference sphere (new BSF) that best fits to the peripheral corneal area excluding the central area with 4 mm in diameter centered on the thinnest point. The elevation map considering the new-BSF was subtracted from the elevation map with the standard BSF that best fits the total corneal area. The highest difference between the elevation maps in the central 4 mm area was noted for anterior and posterior cornea. Corneal biomechanical properties are obtained by the Ocular Response Analyzer to calculate corneal hysteresis and corneal resistance factor. Dr. Ambrosio illustrated how he used these combined measurements to detect ectasia susceptibility in a patient who would have been considered a gook LASIK candidate based only on topography and pachymetry measurements. He also showed cases with low central corneal thickness or an asymmetric bow-tie that would have qualified as forme fruste keratoconus under traditional measurements, but were indeed good candidates for LASIK. “Biomechanical customization means better screening and better planning,” Dr. Ambrosio said. Dr. Ambrosio has financial interests with Alcon, Allergan, Oculus Optikgeraete, Reichert and Visx. Back to Top
Preventing anterior capsular tear in intumescent cataracts Daniel A. Badoza, MD, of Argentina won a “Best Paper Award” for his presentation showing how a capsulorrhexis made in “one-and-a-half” turns decreases the risk for extension of the anterior capsular margin, especially in intumescent cataracts. He reviewed a case in which an anterior capsular tear occurred while the capsulorrhexis was made. To prevent the tear from extending, he started the rhexis near the visual axis, under high viscoelastic-induced IOP, and increased progressively its diameter in one-and-a-half turns of the anterior capsule margin. In 40 eyes with intumescent cataracts, Dr. Badoza said this technique showed no extension of the anterior capsule tear to the posterior capsule, allowing a well-centered rhexis. Back to Top
It’s time for ophthalmologists to progress beyond Benjamin Franklin’s contribution to eye care Marguerite B. McDonald, MD, today presented a paper showing how much improved the new optimized progressive lenses are compared to standard progressive designs, and urged ophthalmologists and opticians to advocate for them among their patients. She added that they are also helpful in dealing with the unhappy multifocal IOL patient. “It is a dismaying fact that just under 50 percent of prescription eyeglasses wearing presbyopes currently wear bifocals, a lens technology that Benjamin Franklin is thought to have invented some 220 years ago, or trifocals,” she said. To put this into perspective, imagine if 50 percent of all refractive surgery patients still received radial keratometry despite the availability of significantly better surgical options? “Ophthalmologists are uniquely positioned to understand the impact higher order aberrations can have upon vision and to grasp the benefits of a refracting surface that has been optimized with wavefront technology,” Dr. McDonald said. “It is up to the doctor and opticians to become lens technology advocates and to actively help patients migrate to what truly are new and improved lens options.” Dr. McDonald described the engineering behind the new Varilux Physio, which brings together the application of wavefront measurement and digital surfacing technologies to the optimization of progressive lens optics. As a result, the Varilux Physio lens enhances the quality of the wavefront that reaches the presbyope’s eye, no matter the direction of gaze. In a multicenter European study designed to evaluate if a wavefront-optimized design provides better vision than conventional progressive designs, Varilux Physio was dispensed to 609 randomly selected presbyopes with corrections from -10.00 to +6.00 D, up to 4.00 D of cylinder, and add powers from 0.75 to 3.50 D. The patients, all of whom paid for their lenses, were surveyed at three weeks. For near, intermediate, and distance, respectively, subjects reported “clearly wider/wider” fields. They also reported “clearly better/better” (72 percent, 65 percent, and 67 percent) vision with the wavefront-optimized lens compared to their conventional lenses. And, 72 percent rated their overall quality of vision as “clearly better/better” with the wavefront-optimized lens than with their prior lenses. Preference for the wavefront-optimized design was consistent, regardless of ametropia, subject’s age, or previous type of lens. Compared to a leading conventional progressive lens design, Varilux Panamic, the wavefront-optimized Varilux Physio lens provided: - Three times less higher order aberration at distance
- Reduced amplitude and enhanced orientation of residual astigmatism in the intermediate zone resulting in a 30 percent wider field of comfortable intermediate vision
- A 10 percent reduction in maximum defocus in the near zone for improved power control along a greater vertical area, resulting in an expanded field of near vision acuity
Dr. McDonald has financial interests with AMO, Alergan, Bausch & Lomb, Inspire Pharmaceuticals, Essilor, OASIS Medical and Santen. Back to Top
Update on the micro-bypass stent for combined cataract and glaucoma surgery Carlos Buznego, MD, of Florida, won a “Best Paper Award” for his presentation of an 18-month analysis of the iStent trabecular micro-bypass stent (Glaukos). The iStent, which is not yet commercially available or approved by the U.S. Food & Drug Administration (FDA), is inserted through a clear corneal incision under gonioscopic control while directly visualizing the angle and trabecular meshwork. The technology allows aqueous to flow directly into the canal toward the episcleral drainage system, and it avoids the trabecular meshwork. When implanted with a micro-bypass stent after combined cataract surgery, uncontrolled primary open-angle glaucoma patients showed significantly reduced IOP and medication use, Dr. Buznego said. In the 58 patients studied, there was a mean IOP reduction of 5 mmHg and a medication reduction from 1.6 to 0.4. There were some postoperative complications related to glaucoma: - 1 paracentesis to reduce IOP at one month.
- 3 stent procedures—1 reposition/2 replacement
- 6 malpositioned stents with apparent function-- no Rx required (reduced IOP with less meds)
But there was no reported incidence of hypotony, post-surgical flat chambers and/or choroidal effusion, he said. A prospective randomized clinical trial (iStent placement with cataract surgery compared to cataract extraction alone) is currently in progress in the US to seek FDA approval. Dr. Buznego has financial interests with Alcon, Allergan, Aqumen, Glaukos Corporation, Inspire Pharmaceuticals, Ista Pharmaceuticals, Lenstec, Rapid Pathogen Screening and Sirion. Back to Top
A twist In a refreshing twist on the traditional Breakfast with the Experts sessions, ISRS/AAO conducted Swimming with the Experts this week in Cancún, México. Klaus N. Ditzen, MD, of Germany, jumped in first with a question about femtosecond lasers. Cesar C. Carriazo Escaf, MD and Fracisco Sanchez Leon, MD made waves with their response. Back to Top
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