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Sub-Bowman’s will be next trend in laser refractive surgery, surgeon predicts
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LAS VEGAS — Sub-Bowman’s keratomileusis will become the next trend in laser refractive surgery, combining advantages of both PRK and LASIK, a surgeon speaking here predicted.
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In sub-Bowman’s keratomileusis, or SBK, a femtosecond laser is used to create a corneal flap just below the level of Bowman’s membrane, at a depth of 60 µm to 70 µm, according to Daniel S. Durrie, MD. This is “the optimal flap,” he said.
At the American Academy of Ophthalmology meeting, Dr. Durrie discussed results from a prospective, randomized, contralateral eye study comparing SBK and surface ablation in 100 eyes of 50 patients.
The IntraLase FS (IntraLase Corp.) was used to create the 60-µm to 70-µm flap, and the ablations were performed using Alcon’s LADARVision CustomCornea excimer laser system.
Dr. Durrie used the Visante OCT (Carl Zeiss Meditec) to measure flap thickness at several locations and found a standard deviation of less than 5 µm at any point.
“[The cornea] is flat as pancakes,” he said. “This is important because if you go thin, you must have consistency.”
Eyes treated with the SBK procedure showed decreased postoperative dry eye, lower reported corneal sensitivity, similar amounts of higher-order aberrations and a higher rate of overall patient satisfaction, Dr. Durrie said.
“We are now moving beyond PRK and LASIK,” Dr. Durrie said. “We will be hearing a lot about SBK.”
Other highlights from the AAO meeting are featured in this article. Most of these items appeared originally as daily coverage from the meeting on PCONSuperSite.com.
Multifocal ablation safely treats presbyopic hyperopes
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Multifocal corneal ablation, also known as presby-LASIK, appears to effectively correct presbyopia and hyperopia simultaneously, according to a surgeon speaking here.
Marguerite B. McDonald, MD, discussed the outcomes of two recent studies of the procedure. A study performed by Canadian investigators included 75 eyes of 43 hyperopic presbyopic patients. The patients had preoperative sphere ranging from +1.7 D to +3.5 D and preoperative cylinder ranging from +0.43 D to +1.5 D. At 12 months after undergoing multifocal ablations, 100% of patients had achieved 20/20 or better binocular uncorrected distance vision, Dr. McDonald said.
A second study, performed by investigators in the United States, included 20 patients. Preoperatively, sphere ranged from +1.5 D to +2.5 D and cylinder ranged from +0.3 D to +1 D. At 3 months’ follow-up, 73% of patients had achieved 20/20 or better and all patients had achieved 20/25 or better in the corrected eye, she said.
No eyes lost two or more lines of best corrected visual acuity at 3 or 6 months follow-up, Dr. McDonald noted.
The results are “very reassuring because this is definitely a high wire act to create a multifocal surface over the visual axis,” she said.
Clinical results, safety led surgeon to “hang up her microkeratome”
Improved clinical results and superior safety with surface ablation procedures are the principal reasons one surgeon said she has abandoned LASIK in recent years.
Dr. McDonald, who pioneered PRK 20 years ago, outlined the reasons why she has recently returned to corneal surface ablation procedures in a presentation titled “Why I hung up my microkeratome.” It was the opening presentation here at the Refractive Surgery Subspecialty Day.
Problems experienced with surface ablation in the early days of excimer laser use in refractive surgery, such as delayed visual recovery, pain and haze, have been reduced with new advanced surface ablation techniques, such as epi-LASIK, she said.
“I’m not the only person who thinks maybe we should hang up our microkeratomes,” Dr. McDonald said. She cited data from Market Scope indicating that refractive surgeons are increasingly adopting or returning to surface ablation procedures, either completely or as a growing percentage of their overall refractive surgical mix.
Regarding safety, she said, “If you don’t have a flap, you can’t have flap complications.” A surface approach is also safer in thinner, steeper and flatter corneas, she said.
In terms of efficacy, results with customized ablation treatments are even better on the corneal surface than with LASIK, she said.
“Creation of the flap leads to an unpredictable biomechanical change in the cornea, and the wavefront map is altered in an unpredictable fashion,” Dr. McDonald said.
She cited results of two recent unpublished studies of customized ablation using different laser systems, suggesting that the benefit of surface ablation is “independent of the platform used.”
A study by David J. Tanzer, MD, and colleagues compared PRK and LASIK with the Advanced Medical Optics Visx Star S4 in 50 patients. At 6 months postop, 71% of PRK patients were within 0.25 D of target, compared to 56% of LASIK patients, Dr. McDonald said. She also cited work by Anelise D. Wallau, MD, and colleagues, in a study comparing custom PRK and custom LASIK with the Alcon LADARVision system. In that study as well, results with PRK were superior to those with LASIK, she said.
In addition, Dr. McDonald reviewed the results of a multicenter study, in which she participated, evaluating the Norwood EyeCare epikeratome and the Visx Star S4. In that study, in 71 patients with 3-month follow-up, 90% of patients were within 0.25 D of plano, and 100% were within 0.5 D.
Dr. McDonald acknowledged that visual recovery after PRK is slower than after LASIK, but she said “the gap is narrowing.” And she said an aggressive pain-management regimen that includes oral prednisone, ice packs and a topical nonsteroidal anti-inflammatory drug has helped to make her patients more comfortable in the first few days after surgery.
Anti-VEGF drug shows promise for treating ROP
Infants with retinopathy of prematurity treated with a vascular endothelial growth factor inhibitor showed an improvement in vascular activity but a risk of tractional retinal changes, according to Kimberly A. Drenser, MD, PhD.
Dr. Drenser discussed results in six patients with retinopathy of prematurity who were treated in one eye with pegaptanib sodium (Macugen, Pfizer/Eyetech) in addition to laser treatment.
“All six eyes showed a remarkable reduction in exudative vascular activity within a 4-week period after the injection,” Dr. Drenser said. She added that this improvement was sustained for a number of months without toxicity.
She continued, “There is an important note here that any eyes that appeared to have any vitreoretinal deduction abnormalities or even early proliferation seem to be at high risk of having tractional changes following anti-VEGF treatments.”
Dr. Drenser expressed concern that while there was “early impressive decrease in vascular activity” and a delay of retinal detachment, any fibrotic tissue with proliferative changes aggressively underwent tractional change.
“Our feeling from both retinopathy of prematurity and FEVR [familial exudative vitreoretinopathy] is that it does effectively treat vascular activity, but it does not prevent tractional changes in the eye,” she said.
The theory, she explained, is that transforming growth factor beta, a natural antagonist of VEGF, is unopposed when VEGF is blocked and may exacerbate proliferating tissue and cause retinal detachment with tractional changes.
“Basically we think these are some early steps in looking at how we can better realize some of our new therapies for treating pediatric vitreoretinopathies, and we hope further studies in this area will help us to fine-tune the treatment modalities currently used,” Dr. Drenser said.
Surgeon describes initial experience with Allegretto Wave Eye-Q
One surgeon described his positive initial experience with the recently launched Allegretto Wave Eye-Q laser during an event sponsored by the manufacturer, WaveLight AG.
Roberto Pineda, MD, reported his experience after using the laser for 3 weeks. “This laser is impressive,” he said. “It has the widest range of FDA-approved wavefront-based treatments.”
Dr. Pineda said reduced treatment times with the laser can lead to less corneal drying, better predictability and better patient comfort.
On postoperative day 1, 50% of patients had uncorrected visual acuity of 20/20 or better, and at 1 week postop 71% were 20/20 and 92% were 20/25 or better.