While some doctors have noticed that patients are more likely to be slightly farsighted than nearsighted after LASIK, doctors have had no way to predict which patients would be affected, MacRae said. If a doctor adjusted all of his or her surgeries to avoid the problem, then the other 80 percent of patients would wind up slightly nearsighted.
The new formula takes the guesswork out of the picture and establishes a scientific basis for the phenomenon.
The software developed by Venkiteshwar and MacRae controls how the laser beam dances around the surface of the cornea during a LASIK procedure, allowing the surgeon to sculpt the cornea into just the right shape so that it produces as flawless an image as possible. During a procedure that typically might last anywhere from 15 to 60 seconds, the laser beam hits the cornea about 50 times per second, with generally 750 to 3,000 pulses. The timing and aim, controlled by both the surgeon and the software, have to be precise.
By taking into account the unique anomalies in each persons eye, the formula predicts which patients are most likely to be slightly farsighted after a LASIK procedure, then adjusts the laser to avoid that outcome.
Ironically, Venkiteshwar and MacRae found that the cause of the shift was the new capability doctors have to fix subtle visual imperfections that werent even known to exist until David Williams, Ph.D., at the University of Rochester developed a system to see them.
Williams' system opened the door, for the first time in history, to the possibility of fixing not only the three major flaws in the eye that reading glasses and contact lenses have corrected for decades, but also approximately 60 additional imperfections that were never known before. Nearly everyone has these flaws in their eyes to
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Contact: Tom Rickey
tom_rickey@urmc.rochester.edu
585-275-7954
University of Rochester Medical Center
18-Sep-2006