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- 作者:罗岩|发布时间:2009-07-16|浏览量:2025次
Implantable contact lenses beat LASIK for higher degrees of 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.北京协和医院眼科罗岩
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, outgoing president of the American Society of Cataract and Refractive Surgery.
She thinks that somewhere around ?6D or ?8D and above, surgeons will turn from laser to ICL procedures. For lower degrees of myopia, she said LASIK is “incredibly successful” and warned of a potential added element of risk for cataract or endophthalmitis when penetrating the eyeball. She said cataract surgeons who may “love to swim around in the anterior chamber” may adopt ICL procedures even for ?4 or ?3D eyes, especially if they feel uncomfortable with laser refractive surgery.
Dr. McDonald pointed out high myopes 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 major limitation of the current study is that eyes or patients were not randomised to the ICL or LASIK procedures but that the series were merely run concurrently. With only one year of follow up in the study, she looks forward to seeing data five years out.
The trial results appeared in the journal Cornea 2003;22(4):324-331.
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