The techniques appear crucial for minimizing unwanted side effects and allowing patients, most of whom now have vision of 20/16 or better, to enjoy the full effects of a type of enhanced vision that wasn't even a twinkle in the eye of doctors 20 years ago.
"We're trying to improve upon something where people already come out and say, "Wow, I've never seen that well." We're learning how to make an extremely effective surgery even better," says MacRae, professor of Ophthalmology and Visual Science at the University of Rochester Medical Center and medical director of Strong Vision.
The field of supervision or "customized ablation" had its genesis in laboratory work in the early 1990s at the University of Rochester, where a team led by David Williams discovered how to use a laser beam to take the best images ever of the inner eye in people, then used the new technology to discover dozens of defects – "higher-order aberrations" – in our vision that were previously unknown.
Around the same time, the popularity of refractive surgery, where surgeons use a laser beam to sculpt the cornea to improve vision, was beginning to take off. Williams' research helped bring to Rochester MacRae, a pioneering refractive surgeon, and the two teamed up at the University of Rochester Eye Institute in an effort to improve eyesight to a degree previously unheard of.
Using Williams' laboratory work as a road map to the intricacies of the inner eye, MacRae developed customized ablation, a custom version of refractive surgery that corrects for the previously unknown nuances of a person's vision. In the earliest days of refractive surgery, doctors didn't even know that "higher-order" aberrations existed; soon MacRae was one of the first in the world to fix these defects and turn out patients who said their vision had never been crisper. Since then MacRae has used Williams' research to directly improve the vision of hundreds of patients: In the largest study, seven out of 10 patients saw their vision improve to 20/16 or better, and 97 percent said they had marked or extreme improvement. Because of the research the technique is now widely available and has been used to improve the eyesight of tens of thousands of patients worldwide.
"This technology has revolutionized the way people see, and the way we think," says MacRae. "While fixing traits like near-sightedness and astigmatism are still the fundamentals, now we're able to improve on problems that in the old days we didn't even know existed."
In New Orleans MacRae discussed three recent findings by his team that boost vision quality even further:
- Increasing the size of the surface of the eye being treated helps prevent a visual defect known as spherical aberration. Geunyoung Yoon, Ph.D., a colleague who works closely with MacRae, has untangled how the laser can affect spherical aberration, which can cause blurry vision and sometimes results in patients seeing halos around lights at night. The team found that increasing the area of the "treatment zone" on the eye reduces this side effect dramatically.
- Precise positioning of the laser during surgery is vital to prevent a defect known as coma, which causes lights to appear fuzzy and can result in a sharp and annoying glare from lights at night. In a recent study, MacRae's team got its best results when the tracking device used to position the laser was within 200 microns – about three times the width of a human hair – of the most desirable spot. Better tracking devices in recent years have helped physicians position the beam precisely, MacRae says, reducing in patients the amount of coma, whose effect on vision can rival that of a bad case of astigmatism.
- Careful manipulation of the flap of the cornea that is cut during surgery is more crucial than was previously thought to achieve the best vision possible. MacRae has found that keeping the area dry during surgery helps prevent swelling that can make it difficult for a surgeon to bring the cornea back together meticulously.
Since the field is still emerging, it's crucial for patients to choose their physician carefully, says MacRae, who has been honored nationally for his work and who is an author of the book Wavefront Customized Visual Correction: The Quest for Supervision II. While price is always a concern for consumers, MacRae says that sometimes a higher price covers costs that contribute to patient safety. For instance, a doctor like MacRae turns away significant business after investing hours with a patient because he discovers that many patients – around 20 percent – are not good candidates for refractive surgery and might have troublesome side effects. MacRae and other top doctors also use extensive, seemingly repetitive screening techniques to check traits such as the thickness of a person's cornea, which is crucial to the surgery, as well as the characteristics of a patient's pupil.
"The bottom line is that if you use state-of-the-art techniques and you choose your patients carefully, you should get outstanding results. While most of our patients are ecstatic with the results, the field is so young that there are constantly discoveries that should improve patients' vision even more," says MacRae, who has helped train nearly 1,000 physicians around the country about refractive surgery.