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Loss of central ICL vaulting associated with anterior subcapsular cataract in myopes
Ophthalmol. 2010;117(8):1506-1511.
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Central vaulting of a posterior chamber phakic IOL diminished steadily for up to 10 years, a study found. In addition, the investigators reported a significant link between insufficient ICL vaulting and the development of anterior subcapsular cataract.
"If an ICL is chosen for the correction of myopia, targeting for the greatest possible postoperative central vaulting is advised to achieve safe and complete vaulting for several years," the study authors said.
The retrospective study included 84 eyes of 84 patients implanted with the ICM-V4, the latest model of the posterior chamber phakic Visian Implantable Collamer Lens (Staar Surgical). In addition, 27 eyes of 27 patients were implanted with older ICL models.
Investigators conducted complete ophthalmic examinations before surgery as well as postoperatively at 1 week, 1 month, 3 months, 6 months and annually.
Patients in the ICM-V4 lens group were followed for a mean of 74.1 months; patients in the earlier model group were followed for a mean of 96.3 months.
Study data showed that at 1-week follow-up, postoperative vaulting was 466 ?m in the ICL-V4 eyes and 321 µm among the earlier model group. The difference was statistically significant (P = .002).
At 10 year's follow-up, mean central vaulting was 184 µm in the ICM-V4 eyes and 138 µm among the earlier model group. Average annual loss of central vaulting was 28 µm in the ICM-V4 group, the authors said.
Results showed a correlation between loss of central vaulting and cataract development.
An early postoperative vault of 700 µm or more would likely provide adequate vaulting for 25 years or longer. Postoperative vault of 400 µm or more may ensure safe vaulting for at least 10 years, the authors said.
Medical interventions, whether pharmacologic or surgical, need to be evaluated based on safety and efficacy. If you are dealing with a potentially fatal affliction, efficacy trumps safety. In refractive surgery the opposite holds true. Excimer ablative techniques have a long track record of both safety and efficacy. Safety concerns with laser refractive surgery are usually observable in the relative short term (scarring, flap complications, iatrogenic ectasia). The paper by Schmidinger, Lackner and Skorpik is unique for its long term follow-up (mean greater than 6 years) of the posterior chamber phakic ICL and raises some very disconcerting issues. The authors document a progressive loss of clearance between the natural and phakic lens and an anterior subcapsular cataract rate of 28% after a mean follow-up of less than 4 years. The study population in this subgroup averaged only 36 years (range 10 to 46) and so cataract surgery in this group should not be viewed as a benign intervention, as the loss of natural accommodation cannot be dismissed. For some refractive surgeons who advocate phakic lens implantation as the procedure of choice for all but low myopes, citing better efficacy, this paper should be eye-opening.
– Michael W. Belin, MD
Professor of
Ophthalmology and Vision Science, University of Arizona, Tucson, Ariz.