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A new aspheric treatment for presbyopia, P-curve, considers both the total Q value and the corneal asphericity among other parameters to induce the negative spherical aberration that is lost with aging.
"This is a new solution to fix presbyopia symptoms without complaints, with good vision quality, and minimal loss of contrast sensitivity," said Dr. Pinelli, scientific director, Laser Ocular Microsurgery Institute, Brescia, Italy. "The algorithm can be applied using different lasers and the results are similar. In addition to presbyopia, the algorithm can be used for LASIK and other surgical techniques."
He used a proprietary laser (Technolas 217 ZY, Bausch + Lomb) for his patients.
"There is no one surface in the human eye that is not aspheric," he said. "Therefore, the traditional concept of multifocality is not applicable because the asphericity index is much more acceptable for the quality of the visual acuity."
Dr. Pinelli demonstrated that the range of spherical aberrations varies widely in day and night vision. He emphasized that considering the Q value (i.e., the corneal asphericity) by itself is insufficient.
"For good quality of vision and excellent distance and near vision we need [to consider] more details and parameters," Dr. Pinelli said.
Candidates for bilateral treatment
Patients with myopia, astigmatism, hyperopia, and emmetropia are candidates for the bilateral treatment. The treatment works by causing a switch to negative spherical aberration with less bending of light rays in the periphery of all rays that come to a single point of focus (i.e., the algorithm produces the negative spherical aberrations that are lost with increasing age).
"The treatment customizes the natural prolateness of the cornea to obtain far and near vision," he said. "The final curve is not multifocal but is a prolate and aspheric shape with the pre-planned flat area on the top of the curve."
Dr. Pinelli presented the experience of his group in 200 patients after 2 years using the P-curve and described the near visual acuity, uncorrected visual acuity, distance uncorrected visual acuity, sphere, cylinder, and spherical equivalent were quite good 1 year after the procedure. The best refractive results, he noted, are achieved in patients with plano vision.
At 2 years postoperatively, he said that the results seem to be encouraging for the future. Patient satisfaction postoperatively was high.
"With this very smooth curve, we eliminated glare, halos, and night vision complaints, which are frequent in the multifocal cornea," he said.
Dr. Pinelli and colleagues are in the process of standardizing the parameters considered using P-curve. He said he expects that the program will be commercially shortly.
"This treatment seems promising," Dr. Pinelli concluded. "In a maximum of 2 to 3 years, we believe we will be able to treat all patients with equally good results."
Roberto Pinelli, MD
Dr. Pinelli has no financial interest in the subject matter.