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Phakic IOL better than LASIK for high myopia
By Daniel Keller
Implantable contact lenses (ICL, Staar) appear to have the edge
over LASIK for treatment of myopia, particularly in cases of higher
refractive error, a large multicentre study suggests.
US researchers compared the effects of ICLs and LASIK in a study
involving nearly 800 eyes. Nineteen surgeons implanted ICLs in 210
eyes of 121 patients at 14 sites, while 11 surgeons performed LASIK
on 559 eyes of 358 patients at the Davis Duehr Eye Center in Madison,
Wisconsin, USA. Patients had pre-op manifest refractions of -8D
to -12D, with a mean of -9.1D for the LASIK group and -9.8D for
the ICL group. The mean ages of patients were 38.8 years and 36.3
years for the LASIK and ICL groups respectively.
Study co-author John Vukich MD noted that the study was not randomised
but followed concurrent series of patients to evaluate the results
a multi-surgeon LASIK centre could expect in moderate to high myopia
patients similar to ones in the ICL clinical trial conducted at
15 sites.
"At every point post-operatively at which we measured, the
ICL compared favourably or was superior to LASIK in terms of quality
of uncorrected visual acuity, in terms of attempted versus achieved
correction, and in terms of residual refractive error," Dr.
Vukich said.
Every measure of vision six months after the procedures favoured
ICLs over LASIK. Essentially all patients had uncorrected visual
acuity (UCVA) worse than 20/200 before the procedures. After surgery,
more ICL patients had UCVA of 20/20 or better at all time points
compared to the LASIK group (p<0.01). Similarly, the overall
distribution of UCVAs favoured ICL at all time points (p<0.05).
Best spectacle corrected visual acuity (BSCVA) was better with ICLs
at all visits from one week through one year post-operatively. Improvement
in BSCVA (two or more lines) was statistically significantly better
with ICLs compared to LASIK at one week and at six months. At the
six-month and one year visits, almost half the ICL patients had
improvements in BSCVA of at least one line, compared to 29% of the
LASIK patients. No patients in either group lost more than two lines
at one year.
ICL implantation gave significantly more predictable results at
all visits between one week and one year follow up. Similarly, the
stability of refraction was better with the ICLs at all visits.
Refractive errors stabilised by one month for the ICL cases but
continued to change throughout the one-year follow up for the LASIK
group.
During this period, only one ICL patient required a secondary surgery
to reposition the lens two weeks after the initial surgery. No one
required lens removal or replacement, and no clinically significant
opacities occurred in the natural lens. Among the 210 eyes initially
treated with ICLs, nine (4.3%) underwent secondary LASIK procedures
and two (1%) underwent astigmatic keratotomy procedures.
Dr. Vukich said occasional ICL patients had early intraocular pressure
elevations that resolved. None developed glaucoma or had other long-term
complications.
LASIK complications were far more common. Of the 559 initial LASIK
eyes, 128 (23%) received laser enhancements during the one-year
follow up. Other complications were diffuse lamellar keratitis (3.0%)
and striae in the corneal flap (3.0%)
Dr. Vukich said the ICL may provide some advantages over LASIK in
the higher myopic range, including sparing of tissue and allowing
greater structural integrity to the cornea. The reversibility of
the ICL procedure is another advantage.
He noted that while LASIK with commercial excimer lasers has been
approved in the U.S. for up to -14D of myopia, the procedure may
not be feasible for patients with more than -7D because of the amount
of corneal tissue that needs to be removed for correction.
ICLs have been available in Europe since the early 1990's. Earlier
designs raised concerns about induced cataract, but the V4 design,
the only one currently available, appears to have eliminated these
problems. Version 4 has increased the "vaulting" or clearance
from the crystalline lens compared to earlier ICL models. V4 follows
the contour of the natural lens but does not touch it.
"That anatomic separation of the implant from the crystalline
lens has had a dramatic effect in reducing the incidence of cataracts
associated with the implant," Dr. Vukich said.
In the U.S. clinical trials at three years, the incidence of cataract
was 0.9%. These complications could be remedied through cataract
surgery, a substantial benefit over LASIK surgery, where the rare
complications "are commonly not easily fixed," he noted.
Dr. Vukich predicts that most surgeons will consider ICLs for their
patients with higher degrees of myopia (-8D and above), those who
have corneal irregularities, or those who may not be suitable for
LASIK for other reasons. As they gain experience, he says surgeons
may offer the procedure to patients in the lower range of myopia.
A study is in progress evaluating the use of ICLs in -3 to -8D eyes.
"Somewhere between -8 and -12 dioptres, you have to draw the
line and say 'I'm not doing laser any more'," commented Marguerite
McDonald MD, immediate past president of the American Society of
Cataract and Refractive Surgery.
She thinks that somewhere around --8 to -12 D and above, surgeons
will turn from laser to ICL procedures. Some surgeons may start
implanting phakic IOLs for even lower degrees of myopia, but for
most surgeons, she said, LASIK is "incredibly successful"
for lower degrees of myopia. Dr McDonald warned of a potential added
element of risk for cataract or, rarely, endophthalmitis when penetrating
the globe. She said cataract surgeons who may "feel comfortable
in the anterior and posterior chambers" may adopt ICL procedures
even for -4 or -3D eyes, especially if they feel uncomfortable with
laser refractive surgery on the cornea.
Dr. McDonald pointed out that high myopes feel that they are "optical
cripples" because they are essentially incapacitated without
their glasses, so even though the ICL procedure is more invasive,
they are quite likely to accept it.
She pointed out one limitation of the current study: the eyes or
patients were not randomised to the ICL or LASIK procedures; the
series were merely run concurrently. With one year of follow up
in the study, Dr McDonald congratulates the authors but also looks
forward to seeing data five years out.
The trial results appeared in the journal Cornea 2003; 22(4):324-331.
John A. Vukich, MD, Surgical Director,
Davis Duehr Dean Center for Refractive Surgery
Davis Duehr Dean Eye Center, Madison, Wisconsin, USA
javukich@facstaff.wisc.edu
Marguerite McDonald, MD
Clinical Professor of Ophthalmology
Tulane University School of Medicine, New Orleans, LA
margueritemcdmd@aol.com
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