AUG 24, 2010
Researchers evaluated the central and midperipheral vaulting of the posterior chamber phakic intraocular collamer lens (ICL; Staar Surgical Inc., Monrovia, CA) after it was implanted in patients with moderate to high myopia. They found that central vaulting diminished steadily for up to 10 years. In addition, they found evidence of a significant link between insufficient ICL vaulting and the development of anterior subcapsular cataract.
The retrospective analysis included 84 patients (84 eyes) implanted with the latest model of the posterior chamber phakic intraocular collamer lens, ICM-V4. An additional 27 patients (27 eyes) were implanted with earlier ICL models. Investigators conducted complete ophthalmic examinations before surgery as well as postoperatively at one week, one month, three months, six months and annually. Central vaulting was measured using the Jaeger device. They also used optical coherence tomography from 2006 on. 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.
Mean postoperative central vaulting was 466 μm in the V4 group and 321 μm in the early- model group. They observed a significant and continuous reduction in central vaulting with both models from six months postoperatively to the 10-year follow-up. At 10 years, mean central vaulting diminished to 184 µm in the ICM-V4 eyes and 138 µm among the earlier model group. Patients who developed anterior subcapsular cataract had significantly lower central vaulting than those with clear crystalline lenses, and patients with lower central vaulting had a greater likelihood of mid-peripheral contact between the ICL and the crystalline lens. The mean vaulting was 216 μm at the initial cataract manifestation and 98 μm at the time of cataract extraction.
The authors recommend aiming for the greatest possible postoperative central vaulting to achieve safe vaulting for several years. From their data, a minimum central vaulting of 230 μm appears necessary to ensure total vaulting of the ICL. 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.