Reports from Day 1 of Refractive Surgery and Retina Subspecialty Day
Pioneer in LASIK surgery hangs up her microkeratome to join the "Secret Surface Ablation Society"
Speaking today at the Refractive Surgery Subspecialty Day meeting, Marguerite McDonald, MD, explained why she has limited her practice to surface ablation procedures only. Surface ablation procedures are simpler to perform, safer for both the patients and physicians and most importantly provide superior visual outcomes. “The best LASIK outcomes are not as good as or superior to the best surface ablation outcomes in terms of BCVA, UCVA and MR,” Dr. McDonald said. And the overall safety of surface ablation is outstanding. With no flap, there are no flap complications: no buttonholes, slipped flaps, microstriae, macrostriae, DLK, incomplete or aborted flaps, etc.
She also described early results of a prospective, randomized clinical trial with the Norwood EyeCare epikeratome and the VISX S4 laser that show surface ablation is more accurate. At three months, 90 percent of 71 patients were within 0.25 D of plano and 100 percent were within 0.5 D. Also, higher-order aberrations were either reduced or remained the same.
As far as the drawbacks—increased pain and a slower return of vision—new research is addressing those concerns, making them less of an issue. Better, smoother ablations and postoperative bandage lenses are improving visual recovery. Dr. McDonald is also improving her technique for pain control. Her strategy includes a short-course of oral prednisone that tapers off rapidly over six days (80 mg a half hour before surgery and 80 mg the day after surgery; 40 mg on day two; 20 mg on day three; 10 mg on day four and 5 mg on day five) and 0.05 percent tetracaine allowed up to every hour while awake for the first three days. She also uses NSAIDs four times a day for three days, lots of chilled BSS during surgery and sterile BSS popsicle applied to closed eyes after surgery. She also notes that surface ablation procedures are ideal for the lower-volume ref ractive surgeon because it is safer and easier; an important consideration since, according to a 2004 MarketScope study, 40 percent of U.S. surgeons perform fewer than 50 laser vision correction procedures per quarter (fewer than 16.6 per month).
For all these reasons, Dr. McDonald hung up her microkeratome and joined what she calls the “Secret Surface Ablation Society, because way down deep, we’re shallow.”
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Surface ablation may be here to stay, but slow visual recovery remains a significant drawback
Daniel Durrie, MD, spoke today about the importance of being smooth and cool to optimize visual recovery as well as to reduce pain and haze in surface ablation procedures. His best practice includes using the PTK smoothing mode on the laser and a small 7.5 mm trephine technique (as opposed to typical 9.0 mm), use of 20 percent ethanol for up to 25 seconds, BSS popsicle for 10 seconds before epithelial removal and after ablation, use of modern excimer lasers (Alcon CustomCornea or WaveLight Allegretto), Johnson & Johnson AcuVue Oasis contact lens, Vigamox and Pred Forte q.i.d for one week and Nevanac up to q.i.d for the first 48 hours postop. Still, slower visual recovery is the most significant problem with surface ablation procedures, said Dr. Durrie. Compared to extremely thin-flap LASIK, it could take up to one month before the PRK patient attains legal d riving vision, 20/40 or better vision. “Surface ablation is here to stay but all our efforts should go into improving the slow visual recovery,” Dr. Durrie said.
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Promising early results with extremely thin-flap LASIK
Steven Slade, MD, today reported on three month results from a randomized, prospective, contralateral eye study comparing PRK and Sub-Bowman keratomileusis (SBK). SBK is also known as extremely thin-flap LASIK performed with a 60 to 70 micron flap. “At three months, SBK still had an advantage over PRK in terms of visual recovery.” The difference in visual outcomes may disappear over time, said Dr. Slade, but initial visual acuity is significantly better with SBK. It could take one week to one month for PRK patients to attain legal driving vision, 20/40 or better vision. With PRK, recovery of visual acuity was much slower at one day and became worse at three days. And at one week, visual acuity was no better than on day one. Dr. Slade said patients also preferred their SBK eye after three months and at each interval checked—one week, one month and three months. Patients reported better vision, less pain and less dry eye, though no S chirmer test was performed. He had three month data, and will continue to monitor the results.
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PRK with MMC appears as effective as LASIK in custom surgeries for myopia
Anelise Wallau, MD, today reported on a study that included 44 patients (88 eyes) randomized to receive PRK with intraoperative application of 0.002 percent MMC for one minute in one eye and LASIK in the fellow eye. At six months follow-up, 95 percent of eyes achieved 0.0 or better logMAR UCVA in both groups. All PRK eyes and 97 percent of LASIK eyes achieved 0.0 better BCVA. Significant haze was not observed in any PRK eyes. Aberration data, contrast sensitivity and endothelial cell count were similar in both groups. Also at six months, patients rated their vision as excellent in 67 percent of PRK eyes compared to 58 percent in the LASIK eyes.
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MMC is extending indications for PRK
Although LASIK remains the most popular type of refractive surgery, it’s time to take a look at LASIK alternatives, said Marcelo V. Netto, MD. “PRK is by far the simplest, cheapest and safest way of performing refractive surgery and MMC use is extending PRK indications.” Excellent refractive outcomes have been achieved with PRK after 12 years of followup. MMC has been advocated as an alternative approach to suppressing corneal haze. Although not ideal, MMC is the only clinical option available for reducing corneal haze formation in eyes that have surface ablation for high levels of myopia and hyperopia. Dr. Netto advocates mechanical epithelium removal during PRK to decrease toxicity, since a synergic effect between alcohol and MMC has already been documented. For prophylaxis MMC should be reserved for higher corrections (usually deeper than 85 microns and in case of haze development in the contralateral eye). He recommends 0.02 percent MMC for 12 seconds, or lower concentrations (0.002 percent for 30 seconds) can also be used. However, following previous corneal procedures such as radial keratotomy, corneal transplant and LASIK surgery, it’s necessary to use it in the conventional concentration, 0.02 percent for at least 30 seconds.
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NIH will sponsor head-to-head trial comparing Lucentis and Avastin
Daniel Martin, MD, announced today that The National Eye Institute, part of the National Institutes of Health, will fully fund a comparative study between the two drugs. The multi-center study is expected to cost $16 million and involve 1,200 patients. Dr. Martin said the study, called Complications of Age-Related Macular Degeneration Treatment Trials (CATT), will evaluate the mean change in visual acuity, number of treatments required, change in subretinal and intraretinal fluid on OCT, change in lesion size and cost. But, said Dr. Martin, “This is not just a cost study. Cost is important, but much science needs to be learned here.” Part of the study will assess dosing strategy, comparing administration on a variable schedule, as ophthalmologists want to give it or on a fixed schedule. “There is no significant data to justify how we want to give it,” he said. He expects the study to begin in early 2007. Patients will be followe d for two years. He hopes to report one-year data in 2009. Ophthalmologists will receive a letter soon regarding study participation.
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Engaging and provocative section on intraocular optics
Lucio Buratto, MD, addressed the growing interest in phakic IOLs. Dr. Buratto surveyed the safety of various approaches, noting that the most serious potential complications of phakic IOLs are acute glaucoma, retinal detachment, cataract and endothelial damage. But he also described patient anatomic criteria and surgical precautions that should help avoid these dangers: Determine that the endothelium cell count is at least 2,000/mm2; establish that the chamber depth is at least 2.8 mm; look for wide, open angles and a normally shaped crystalline lens; and cause minimum damage to intraocular tissues.
Does refractive lens exchange (RLE) raise any ethical issues for ophthalmologists? The answer, not surprisingly, is yes, according to Douglas D. Koch, MD. However, Dr. Koch noted that those considerations are not black and white, but rather quite complex, and must include patient participation in the decision. For starters, make sure the Informed Consent reflects the complexity of RLE. And that means explaining that RLE may create such visual annoyances as halos and reduced contrast sensitivity, not to mention enhanced risk for endophthalmitis and retinal detachments. On the other hand, the potential benefits for appropriate patients include successful refractive correction and improved accommodation. Importantly, Dr. Koch advised that patients understand that RLE will eliminate some future options that might be more attractive to some patients, such as better corneal procedures and IOL designs .
Endothelial cell loss was the focus of an update by Keith H. Baratz, MD. Dr. Baratz noted that normal cell density of the endothelium naturally decreases during life, from about 6,000 cells/mm2 at birth to half that by age 20, and eventually as low as 2,200 cells/mm2 by age 80. Not only that, but the range of cell densities among individuals actually increases with age. All of this, of course, is the backdrop for understanding the endothelial response to intraocular surgery. Densities below 1,000 cells/mm2, for example, are more susceptible to trauma during surgery, and in those that have fallen below 500/mm2 the risk for corneal edema is increased. Compounding the loss is surgery itself, which invariably depletes density further. Cataract surgery precipitates an acute endothelium cell loss—between 4 to 15 p ercent after phaco. And subsequent IOL implantation is associated with ongoing chronic loss of density.
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Drug delivery systems considered as various methods of treating or preventing endophthalmitis
Baruch D. Kupperman, MD, PhD, addressed a range of slow-release ocular drug delivery vehicles. Noting that intravitreal administration, such as with ganciclovir for the treatment of CMV retinitis, has been long established as a safe and effective way to localize therapy, Dr. Kupperman described various implants for the posterior segment.
Bausch & Lomb, for example, already markets sustained-release reservoirs of ganciclovir, and its fluocinolone acetonide reservoir for the treatment of uveitis is also under study for diabetic macular edema. Another version of FA delivery is under study by Alimera, as is a helical coil of triamcinolone acetonide by Surmodics.
Dr. Kupperman also mentioned that Posurdex, a biodegradable implant that delivers dexamethasone, is in phase 1/2 trials. Results show dose-dependent visual improvement in up to 35 percent of patients with macular edema who had not responded to standard therapy.
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