Laser Treatment Treats Extreme Nearsightedness and Astigmatism

October 19, 1999
News Office: Alice Trinkl (415) 502-6397

A new laser that treats the full range of nearsightedness and astigmatism is available at the UCSF Vision Correction Center.

The excimer laser, approved by the Food and Drug Administration and manufactured by Nidek Inc., allows eye specialists to treat extreme degrees of nearsightedness and astigmatism.

"The accuracy of the Nidek laser is excellent, allowing treatment to extend to the highest ranges of nearsightedness and astigmatism currently available on any laser system," said Dr. David Hwang, an ophthalmologist and co-director of the UCSF Vision Correction Center. "We are excited about the approval because patients can now take advantage of the latest technology in vision correction."

UCSF, one of six sites nationally to test the laser through FDA clinical trials, has been studying the laser since 1995. Hwang served as the principal investigator of the study.

The laser corrects nearsightedness and astigmatism by reshaping the curvature of the eye's cornea -- the transparent part of the eye that covers the iris and the pupil and admits light to the interior.

Rather than being applied directly to the cornea as a large beam, the new laser uses a scanning-beam, removing tissue in a smooth and precise fashion across the cornea. This results in fast recovery and better optical quality, said Hwang. In addition, the laser treats a 35 percent larger area of the cornea than conventional laser systems, which may reduce the risk of glare and halo side effects, he added.

UCSF ophthalmologists will use the new laser for both photorefractive keratectomy (PRK) and LASIK procedures, both used to treat nearsightedness with astigmatism, according to Hwang. During the PRK procedure, the laser removes microscopic amounts of tissue from the surface of the cornea to change its shape.

In the LASIK procedure, UCSF ophthalmologists use an instrument called a microkeratome to lift a thin, hinged flap from the corneal surface. They then use the excimer laser to remove a precise amount of the eye's corneal tissue, and then fold the flap back into place without stitches. The LASIK procedure has the advantage of rapid recovery of vision and minimal discomfort following the procedure.

Although FDA approval of the Nidek laser is significant because it allows treatment of patients with extreme degrees of nearsightedness with astigmatism, it is also excellent at treating patients with more typical levels of nearsightedness and astigmatism, said Hwang. Clinical trials of the new laser showed that approximately 95 percent of moderately nearsighted individuals who undergo laser treatment can expect to achieve vision good enough to drive without corrective lenses.

In astigmatism, the cornea, instead of being spherical, is slightly oblong in shape, like a football, which causes light to focus on two separate points in the eye, creating a distorted image in both near and distant vision. Symptoms include blurring or doubling of images.

A normal cornea is round, like a basketball and in normal vision, focuses light rays onto the retina. Nearsighted vision is caused by a steeper curvature in the cornea, forcing the light rays to focus in front of the retina. Farsighted individuals have flatter corneas, which focus the light rays behind the retina.

More than half of the patients with nearsightedness have astigmatism and approximately 70 million people in the United States are nearsighted, said Hwang. Astigmatism also affects patients with farsightedness and no laser has been approved for treatment of both farsightedness and astigmatism, said Hwang. UCSF will serve as one of the principal study sites to test the Nidek excimer laser for farsightedness with astigmatism and began enrolling patients for clinical trials in November.

The UCSF Vision Correction Center is a leading center for diagnosis, treatment and research of vision disorders. Patients interested in more information about the Nidek excimer laser may call the center at (415) 476-2561.