Implantable Lens Provides Predictable, Stable Correction of Moderate to High Myopia for 4 Years

Deborah Brauser

July 15, 2009

July 15, 2009 — The implantation of collagen copolymer lenses provides predictable and stable refractive results in the treatment of moderate to high myopia during a 4-year period, according to results from a retrospective study reported in the July issue of the Archives of Ophthalmology.

"Laser-assisted in-situ keratomileusis (LASIK) has gained widespread popularity as a safe and effective surgical method for the correction of myopia, but patients with high myopia or thin corneas face some restrictions in avoiding the risk of developing keratectasia," write Kazutaka Kamiya, MD, PhD, from the Department of Ophthalmology at the University of Kitasato School of Medicine in Kanagawa, Japan, and colleagues. "Moreover, a large amount of laser ablation may lead to the deterioration of superior intrinsic corneal optical performance."

The study authors write that an implantable lens consisting of a biocompatible collagen copolymer (implantable collamer lens [ICL]; Visian ICL, Staar Surgical Company) was developed as a posterior chamber phakic intraocular lens to rectify these disadvantages. In past studies, ICL implantation has been effective in correcting moderate to high ametropia, and unlike LASIK, this procedure is largely reversible and the lens exchangeable.

However, complications such as cataract formation, endothelial cell loss, pigmentary glaucoma, and papillary blocks have been reported with ICL implantation and are expected to increase with time. For this study, the investigators sought to examine the procedure's long-term clinical outcomes during 4 years in the correction of moderate to high myopia.

"To our knowledge, this is the longest study to assess the refractive outcomes and adverse events of ICL implantation for myopia," write the study authors.

A total of 56 eyes (20 from men and 36 from women) of 34 patients with myopic refractive errors of −4.00 to −15.25 diopters were included in this retrospective observational study. All patients (mean age, 37.0 years; range, 21 – 59 years) had undergone ILC implantation and regular, routine postoperative examinations. Dr. Kamiya and colleagues assessed the safety, efficacy, predictability, stability, and adverse events from exams before the surgery and at 1, 3, and 6 months and 1, 2, and 4 years afterward.

In addition to the usual slit lamp biomicroscopic and funduscopic results, the investigators determined the logarithm of the minimum angle of resolution, or logMar, of the uncorrected and best spectacle-corrected visual acuities, manifest refraction (spherical equivalent), intraocular pressure, and endothelial cell density.

A scanning-slit topography system was used to measure the horizontal white-to-white distance and anterior chamber depth, an autorefractometer measured keratometric readings, an ultrasound pachymeter measured the mean central corneal thickness, a noncontact tonometer was used to assess intraocular pressure, and a noncontact specular microscope was used to determine endothelial cell density.

At 4 years after surgery, the mean logMAR uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA) were −0.03 (0.23) and −0.21 (0.09), respectively.

The safety index (mean postoperative BSCVA divided by mean preoperative BSCVA) was 1.19 (0.25). A total of 18 eyes (32%) showed no change in BSCVA at 4 years, 26 eyes (46%) gained 1 line, 7 eyes (13%) gained 2 lines, 5 eyes (9%) lost 1 line, and no eyes lost 2 or more lines.

The efficacy index (mean postoperative UCVA divided by mean preoperative BSCVA) was 0.83 (0.29), with 53 eyes (95%) having a UCVA of 0.5 and 39 eyes (70%) having a UCVA of 1.0 or better.

While measuring predictability, the investigators found that 44 (79%) and 52 (93%) eyes were within ±0.5 and ±1.0 diopter, respectively, of the targeted correction at 4 years after surgery.

Mean manifest refraction changes of −0.24 (standard deviation, 0.57) diopter occurred from 1 month to 4 years after surgery, and the mean percentage of endothelial cell loss was 3.7% at the 4-year mark.

No significant increase in intraocular pressure or vision-threatening complications occurred during the observation period.

"Implantation of ICLs is safe and effective and provides predictable and stable refractive results in the treatment of moderate to high myopia during a 4-year observation period, suggesting its viability as a surgical option for the treatment of such eyes," write the study authors.

However, "More prolonged careful observation for longer than 4 years is necessary to assess late-onset complications of this surgical technique," they conclude.

"We believe ICL implantation has advantages over keratorefractive surgical techniques such as standard LASIK," the authors add, but they point out that the standard LASIK procedure has been reported to be slightly inferior to wavefront-guided LASIK in visual performance, especially in the induction of high-order aberrations. "Thus, at present, we cannot conclude that ICL implantation provides better clinical outcomes than even wavefront-guided LASIK. We await the results of a randomized, controlled, comparative study of these 2 surgical procedures."

One author reports having been a consultant to Staar Surgical Company, the maker of the study lens.

Arch Ophthalmol. 2009;127:845–850.

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