Laser may treat presbyopia

November 15, 2011

Accommodation restoration through photodisruption of the crystalline lens using an ultra-short-pulse femtosecond laser appears safe and theoretically possible.

Cleveland-Accommodation restoration through photodisruption of the crystalline lens using an ultra-short-pulse femtosecond laser (LensAR) appears safe and theoretically possible. However, results from early clinical evaluation of the technique have been variable, and research is continuing toward developing a technique capable of consistently providing a clinically significant gain in accommodation, said Ronald R. Krueger, MD.

"Our research indicates that the effect of the procedure may depend on the pattern of application of the laser spots, the total energy used, and number of pulses applied," he said. "Based on this information, further study is under way using new algorithms for the laser-created lens patterns in the hope of being able to achieve presbyopia correction without compromise."

Patients enrolled in the clinical feasibility trial ranged in age from 46 to 59 years and had elected to undergo lens removal surgery for refractive reasons. To be eligible for study participation, the patients also had to have best-corrected visual acuity of 20/40 or better and a nuclear sclerotic cataract of grade 2 or less.

"The study was designed to enroll predominantly patients who were moderately presbyopic and with no more than a low-grade cataract," Dr. Krueger said. "With these characteristics, they would represent the target population for the procedure, and any visual acuity change due to the procedure could be identified without possible interference from a visually significant cataract."

At the 2010 meeting of the American Society of Cataract and Refractive Surgery (ASCRS), Dr. Krueger presented the results of the first five treated subjects who underwent the procedure unilaterally using a "waffle pattern" for the photodisruption. Accurate spot delivery with the prototype laser used was guided by a confocal, three-dimensional imaging and biometry system (3-D Confocal Structured Illumination), and the laser was programmed to place spots in a multilayered concentric shell pattern moving from the posterior to anterior layers and sparing the center of the lens. In the waffle pattern, the pulses are aligned in a grid pattern to minimize excessive energy use and possible fracturing of the lens, while facilitating the ability of the natural lens fibers to slide over each other when the ciliary muscle contracts.

Efficacy outcome assessment included objective measurement of accommodation (Grand Seiko autorefractor) and showed that at 1 month after the treatment, accommodation was unchanged in two patients and improved minimally by 0.25 to 0.75 D in two patients, while one patient gained 1.62 D of objective accommodation.

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