Presented by: Edward Manche, MD
Stanford University Medical Center
March 10, 2011
- More options are being developed for people who want to eliminate glasses or contact lenses.
- Wavefront -guided surgeries can measure higher-order micro-irregularities to achieve better vision.
- Femtosecond laser technology allows surgeons to create thin flaps or remove tissue with microscopic precision.
- Eye surgeons are refining the techniques and tools to treat cataracts, the most common eye surgery.
Tremendous advances have been made in refractive surgery for vision correction, and technology continues to be refined, making more options available for more and more people who want to reduce or eliminate their need for glasses or contact lenses.
Refractive eye surgery uses non-thermal lasers to shape the cornea—the “window” that focuses light on the surface of the eye. The laser removes microscopic bits of tissue to flatten the cornea (to correct nearsightedness), steepen the cornea (to correct farsightedness), or smooth out irregularities (to correct astigmatism). Reshaping the cornea allows more focused light to enter the eye, which provides clearer vision.
LASIK and photorefractive keratectomy (PRK) are two of the most common types of laser vision correction. In LASIK, surgeons make a thin corneal flap and then focus an excimer laser on the exposed cornea to remove tissue before replacing the flap.
More Precise Technology
Today several innovations—many of them studied in clinical trials or developed at Stanford—are making these procedures even more refined and opening up options for people who were not able to benefit from refractive surgery in the past, said Edward Manche, MD, director of cornea and refractive surgery at Stanford, at a presentation sponsored by the Stanford Health Library.
One breakthrough involves the use of a wavefront measuring device to guide the laser. Wavefront-guided LASIK and PRK can measure higher-order micro-irregularities to achieve better vision. A computer is used to analyze and measure the surface of the eye, applying contour scanning to make a virtual map. The ophthalmologist can then address both higher-order and lower-order aberrations to provide better vision correction.
For patients with moderate vision problems, studies have shown that wavefront results in 20/40 vision or better in 99.9 percent of cases and 20/20 vision or better in 97 percent of cases.
“This technology can diagnose and measure aberrations that no other system can even see,” said Dr. Manche. “The goal is to produce as good vision as possible, and there has been dramatic improvement over the past two decades.”
Another new relatively new option is femtosecond laser technology, which allows surgeons to create thin LASIK flaps or remove tissue. Femtosecond laser incisions are extremely precise: thousands of rapid pulses create cavitation bubbles that coalesce at a precise subsurface location. This produces a corneal flap at a uniform depth and diameter. The process is painless, and most patients report nearly normal vision by the next day, said Dr. Manche. He also reported refinements to the process, so that the procedure, which used to take about 17 seconds per eye, now only takes approximately 9 seconds.
People who are extremely nearsighted or those who have astigmatism are generally not candidates for refractive surgery. Dr. Manche was involved in a clinical trial to gain FDA approval for a new technique to implant a lens in the eye to correct vision without removing the natural lens. Phakic intraocular lenses allow patients with pronounced nearsightedness to see well without glasses or contact lenses. Initial outcomes of the FDA clinical trials showed 97 percent of patients had 20/40 vision or better, and 65 percent had 20/20 vision or better.
“These results are good because the starting point was in patients with very high levels of nearsightedness,” Dr. Manche said, adding that new flexible lenses show even more promising outcomes.
Other new techniques include collagen cross linking for keratoconus, a degeneration of the structure of the cornea. The technique involves applying ultraviolet light and doses of riboflavin to strengthen the organ, which arrests the progression of the disease. The strategy is still being refined, he added, since the procedure is still relatively uncomfortable and has a prolonged visual recovery.
Other studies are exploring the potential of using femtosecond-assisted laser surgery for cataracts to provide more accurate incisions and placement of the new lenses. Cataracts are a common condition of the aging eye in which the lens becomes clouded, blocking light and blurring vision.
“Cataract surgery is the most common eye surgery performed in the United States,” Dr. Manche said. “This technology allows us to do it with lasers and the steps are standardized, which are more precise and potentially safer than other techniques. There may be less ultrasonic energy delivered into the eye, which may result in less endothelial damage.”
Dr. Manche added that ongoing research are improving outcomes and creating options for people who may not have been candidates for eye surgery in the past. “The field of ophthalmology is changing more rapidly than almost any other field of medicine,” he added. “Future developments may lead to true implants that allow for a full range of vision.”
About the Speaker
Edward Manche, MD, is director of Cornea and Refractive Surgery at the Stanford Eye Laser Center and a professor of ophthalmology. A world-renowned expert in laser and surgical techniques for vision correction, he has performed more than 30,000 laser vision correction procedures and taken part in numerous clinical trials to advance the field. Dr. Manche received his MD from Albert Einstein College of Medicine in New York, and his residency at New Jersey Medial School. He completed a fellowship at UCLA School of Medicine and joined the Stanford faculty in 1996.
For More Information:
About Dr. Manche
Stanford Eye Laser Center
Stanford Eye Institute
Stanford Department of Ophthalmology