Coordinated by Bobby
Christensen, O.D., F.A.A.O.
LASIK Gets Better
A new femtosecond laser should achieve
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
The laser requires
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.
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
Optometric Management, Issue: April 2004