therapeutic insights
LASIK Gets Better
A new femtosecond laser should achieve greater reliability.
By George W. Meers O.D., F.A.A.O.

Hardly a day goes by in clinic that patients don't ask about LASIK. Since 1995, nearly five million Americans have undergone the procedure; nearly every patient knows someone who's had it done.

Get the flap right

Arguably the most important stage in the LASIK procedure is creating the flap, which surgeons traditionally accomplish with a microkeratome. Complications from using microkeratomes range from creating an irregular stromal bed, corneal perforation, varied flap thickness and contribution to central flap striae. The femtosecond laser appears to be the first viable alternative to the mechanical microkeratome available in the United States.

It's a different kind of laser

Professionals use femtosecond lasers in chemistry, machining, engineering and medicine. For LASIK, femtosecond lasers rely on near infrared laser pulses focused at a particular depth below the corneal epithelium. Once focused, a process known as laser- induced optical breakdown occurs. "Microcavitation bubbles" (air bubbles) form, coalesce and create a surface onto which the excimer laser may be applied. Studies have reported this sequence to be extraordinarily accurate, reproducible and safe. While it is a laser, the femtosecond requires little energy and creates minimal thermal damage to corneal tissues.

Femtosecond facts

A recent report in the Journal of Refractive Surgery evaluated the IntraLase femtosecond laser in LASIK in 208 eyes of 122 patients. Investigators excluded patients who had previous corneal procedures, patients undergoing hyperopic procedures or patients who have more than 3.00D of astigmatism from the study. Researchers compared the femtosecond laser to mechanical microkeratomes, paying special attention to the complication rate and the ability to use the femtosecond laser with existing LASIK nomograms.

The most common complication in the study was loss of suction, causing flap creation to be aborted in 1.9% of patients. However, this complication ended up indicating an advantage to the femtosecond laser: When the surgeon using a traditional microkeratome aborts flap creation, he generally must wait three months before attempting to create the flap again. The femtosecond laser, however, allowed a second attempt that same day (most occurred within 45 minutes of the first attempt). Loss of suction was the only operative complication that the investigators encountered.

The results are in

At six months, 114 eyes were available for follow up. No eye had best corrected spectacle acuity of worse than 20/30 and no eyes required retreatment. The authors evaluated the femtosecond laser's compatibility with traditional nomograms and found that they could use them with excellent results. This study was the first reported large clinical series. In the 200 procedures performed in this series, the researchers didn't encounter any postoperative complications.

Investigators are hopeful

The authors felt that the femtosecond laser's ability to be used with a traditional nomogram proved that the femtosecond laser removes an insignificant amount of corneal tissue. The authors also believe that given the precise nature of the femtosecond laser, the ability to adjust flap thickness, hinge position, etc., will further improve LASIK results. These results are preliminary and as more series are reported, the limitations of IntraLase's femtosecond laser will become apparent.

Dr. Meers is staff optometrist and supervisor of the optometric externship program at Bascom Palmer Eye Institute, Miami. Contact him at (800) 329-7000 x4062.

Dr. Christensen has a partnership practice in Midwest City, Okla. He's a diplomate in the Cornea and Contact Lens Section of the American Academy of Optometry. He's also a member of National Academies of Practice.