This article is more than 5 years old. Information may no longer be current.
Asphericity adjustment enhances depth of focus for near and distance
Click Here to Manage Email Alerts
The global optimum and other forms of asphericity adjustment enable refractive surgeons to fine-tune depth of focus and enhance visual acuity, a physician said.
"As adaptive optic technology progresses, so will our refinement of vision and our understanding of this process," Ronald R. Krueger, MD, said at OSN New York 2009.
An aspheric cornea has reduced refractive power toward the periphery, merging light rays to a single focus, Dr. Krueger said.
Like monovision, the global optimum, an aspheric shape in corneal curvature that represents a prolate or oblate Q factor, or degree of sphericity, increases range of focus in the near and distance eye, he said.
Dr. Krueger described a hyperopic case treated with the global optimum. Modification of the corneal shape optimized distance vision and visual acuity in the near eye. Postoperatively, vision was plano in the near eye, with refraction of –1.25 D and reading visual acuity of J1.
"What that meant was the uncorrected vision for distance was 20/60 for a –1.25 D, which should have been more like 20/100 or 20/150," Dr. Krueger said. "But it was a better distance vision because of this modified shape. ... You can see that the distance eye is very uniform-looking, and that's why it's sharp. The global optimum for near tends to give a little bit more of a prolate shape in the center that gives that range of focus for the near."
The global optimum treatment is not currently available in the U.S. However, the P-curve, a technique popularized by Roberto Pinelli, MD, and others, involves over-correction and offers results similar to those of the global optimum, Dr. Krueger said.
"It's not strictly the same as the global optimum," he said. "It's just one of the potential ways of changing asphericity. We're beginning to do some studies looking at the P-curve as one potential aspect."
OSN New York 2010 will be held November 19-21, 2010 at the Sheraton New York Hotel & Towers in New York City. Learn more at OSNNY.com.