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Read Refractive Surgery Outlook Three new paradigms in surgical vision correction Clinical trial results for three new technologies suggest that each shows potential for addressing the visual problems of patients who largely have been left out of the refractive surgery revolution -- low myopes, low hyperopes and emmetropes in their early forties with presbyopia. People with up to 2 D of refractive error generally do not seek out LASIK or PRK treatment because the risks of surgery outweigh the potential benefits. Although excimer laser techniques are available to reduce symptoms of presbyopia, they require visual compromises that emmetropes are reluctant to make. Keraflex may treat keratoconus, post-LASIK ectasia Two electrodes deliver a pulse of microwave energy in annular patterns in the midperipheral cornea. The amount of refractive correction is controlled by varying ring diameters and other parameters. This incisionless procedure improves distance visual acuity without weakening the cornea’s structural integrity and without triggering a wound healing response, said David Muller, PhD, president and CEO of Avedro, Inc. (Waltham, Mass.), the makers of Keraflex. He adds that in trials and clinical use, there have been no reports of complications. Cooling the surface is key But, as with previous unsuccessful attempts at heating the cornea to change refractive power, the company’s initial trials showed that the effect disappeared within a few months. More recent trials addressed this problem with collagen cross-linking, but only in the annular areas affected by the thermokeratoplasty. “Looking at low myopes, we’re seeing good stability at six months postop,” Muller said. “We feel very confident with the procedure in its predictability and stability.” “The cross-linking does not have to be done at the same time as the cornea flattening. This takes a little bit of the pressure off the surgeon, as well as the patient, because if the patient doesn’t like their refractive results, you can let them drift into emmetropia,” he said. Routine retreatments Already in use internationally Avedro hopes to become the first company to make corneal collagen cross-linking available to U.S. patients. Its Phase III FDA trial, in which keratoconus and ectasia patients were treated, reached the required one year of follow-up in May. Refractive regression expected after Opti-K Opti-K is a noninvasive form of laser thermal keratoplasty (LTK) performed with a continuous-wave thulium fiber laser with a sapphire applanation window for corneal epithelium protection. Sixteen laser spots are placed within the stroma in two concentric circles 6.0 mm and 7.2 mm in diameter. Unlike with conductive keratoplasty, Opti-K leaves the corneal epithelium intact. Discomfort is minimal, and patients have clear vision immediately afterward. Presbyopia isn’t stable “Thermal keratoplasty has flopped time and again partly because of the permanence question. But presbyopia isn’t stable. It is progressive, and it changes as we age,” Berry said. Furthermore, after 40 years of age, there also is a natural progressive hyperopic shift, he said. He estimates that a 40-year-old emmetrope would require seven Opti-K treatments by age 70 to have functional near and distance vision. Topography of treated eyes shows alternating sectors of steeper and flatter sections extending from the center of the cornea all the way out to the periphery, Berry said. However, the histology suggests that the laser spots neither destroy tissue nor shrink the collagen. Hydration may be the mechanism In this model, stromal rehydration over time would explain regression. Initially, NTK investigated keratoplasty with the thulium laser as a noninvasive, unilateral treatment to deliver monovision treatment, with perhaps a small element of multifocality to give presbyopic patients better near vision, Berry said. They expected patients to lose a slight amount of distance acuity. “We were pleasantly surprised. We found that patients were not losing distance vision in the eye that had been corrected for near,” Dr. Berry said. Near and distance UCVA improved significantly (P < 0.01 for all follow-up times) in both emmetropes and hyperopes (397 eyes, 199 patients), he said. There were no serious adverse events and no cases of clinically significant induced astigmatism (? 2 D). In one group of emmetropic presbyopes (n = 63), the subjects gained up to 4.2 ± 2.0 lines of uncorrected near visual acuity one day after a staged secondary treatment. The final geometric mean was 2.0 ± 1.9 lines at 26 months. A US FDA trial of Opti-K to correct hyperopia of 1.0 to 2.5 D is underway, with completion of one-year follow-up data expected in November 2012. LaserACE may restore accommodative biomechanism The company behind LaserACE, Ace Vision Group, reported this spring that their laser procedure restored approximately 1.5 to 2.0 D of accommodation in a group of presbyopes in a multicenter international preliminary study. More studies planned Rick Potvin, the company's chief scientific officer and director of clinical research, will manage the studies. Marguerite McDonald, MD, FACS, is Ace Vision's global medical director. The goal of the studies is the objective measurement of accommodation and comparison with an age-matched control group. Additional studies will be conducted in Taiwan, where the company's VisioLite laser recently was approved by the Taiwan FDA, and in two to three European and South American countries that have not been chosen yet, said AnnMarie Hipsley, DPT, PhD, founder and president of Ace Vision. She said that results from these studies will form the foundation for initial discussions with the FDA about the LaserACE procedure, which has not been approved for use in the United States. ASCRS data “We see some pretty compelling findings,” Hipsley said in an interview. “We see an improvement in vision in all ranges, with acuity levels stable for 18 months.” “There is 1.25 D to 1.5 D of accommodation restored by the surgery and this remains stable through the 18-month time period. Significantly, there was no loss of distance vision and no reported increase in visual disturbances. And we see no greater variance in the distance VA than 0.5 D from preoperative levels,” she added. There was an associated 3.1 mm average decrease in IOP, also stable at 18 months, but it is unclear whether this was a true IOP drop or an effect due to the increased plasticity of the sclera. She said the company planned to investigate this further. The visual acuity data reported at ASCRS included these figures:
Patients were assessed with the i-Trace aberrometer (Tracey Technologies) and a custom-designed COAS-HD (AMO-Wavefront Sciences) with Dynamic Stimulation Aberrometry (Optana-Zeiss). The subjects showed 2.0 to 5.5 D of accommodation on these objective tests, Hipsley reported. A separate analysis of accommodation data from 111 LaserACE patients found the postoperative improvements statistically significant (P < 0.001). “Most procedures that address presbyopia compromise a portion of the dynamic vision range, mostly distance vision,” Hipsley said. “The LaserACE is the only current presbyopic procedure to restore natural dynamic accommodation without implants and without altering the existing geometry and optics of the eye.” Diamond matrix pattern ablation The erbium-YAG laser used in the procedure, Ace Vision's VisioLite, already has the CE mark and FDA approval for treating soft tissue around the eyes, although this is without specific claims. It recently was approved by Taiwan FDA, with China FDA approval pending. However, Ace Vision is not making the laser available for sale while the presbyopia trials continue, Hipsley said. Financial Interest Disclosures |