Silicone lenses need capsulotomy twice as often as acrylic

Head-to-head study will digitize PCO images to quantify progression.

Issue: September 1, 2000

BOSTON — Researchers want to further quantify and qualify the differences in the rate of posterior capsule opacification (PCO) of silicone and acrylic lenses. Although the issue has been widely discussed, surgeons continue to conduct head-to-head studies to further refine the clinical picture.

And they are now using digital pictures to help them with that work.

Paul H. Ernest, MD, compared PCO rates for silicone and acrylic lenses. He reported his research at the American Society of Cataract and Refractive Surgery meeting in the talk, “PCO in eyes with AMO Phacoflex II and Alcon AcrySof MA30BA IOLs.”

PCO rate

---PCO rates for silicone and acrylic lenses were compared at 4 years postop. The SI-40NB lens (top) showed a 40% PCO rate. The AcrySof MA30BA lens (bottom) had a 3.7% PCO rate.

Well-documented factors influence PCO, including age of the patient, residual lens epithelial cells, hydrocortical cleavage, implant designs and implant material, he said.

Dr. Ernest conducted a randomized study with no exclusion criteria. He randomized the first operated eye and used the same material in the second-eye surgery, which usually occurred between 2 weeks and 60 days.

He enrolled 159 patients with an average age of 74 years and a range between 53 and 98. He did all surgeries using a temporal approach and sutureless limbal incision. Postoperatively, Dr. Ernest subjectively measured opacification at the slit lamp. Vision was measured using a standard eye chart.

Criteria for YAG laser capsulotomy included observable PCO with a reduction of vision by at least two lines verified by a PAM test. Four years of postoperative data show that silicone lenses form PCO twice as often as acrylics.

Silicone has an average opacification of 33% versus 16% for the acrylic, and also the acrylic has a smaller standard deviation, Dr. Ernest said. Subsequently, twice as many silicone lenses undergo capsulotomies than acrylic lenses.

And 29 patients have required unilateral capsulotomies, 24 with silicone lenses five with acrylic lenses.

The average time before a YAG capsulotomy has been performed is longer in the acrylic group than in the silicone group. Survival analysis for capsulotomy shows that patients who received acrylic lenses fared much better than for the silicone group, he said.

“More eyes with the silicone implants had capsular opacification compared with the acrylic group, and the silicone eyes had a greater area of opacification than the acrylic eyes,” Dr. Ernest said. “Twice as many eyes with the silicone lens required capsulotomies than those with the acrylic lens, and the eyes with the silicone lens developed capsular opacification requiring capsulotomy sooner than the eyes with the acrylic lens.”

Continuing study

He has since expanded the study to use a digitized camera to photograph and transmit the images for analysis.

This analysis method revealed that patients with silicone lenses showed about 35% opacification while patients with acrylic lenses showed about 4% opacification 4 years postoperatively.

Session chairman Randall J. Olson, MD, said, “This is exactly the kind of study that we need where we have head-to-head comparison with objective measures. This is a very important long-term study.”

For Your Information:

Paul H. Ernest, MD, can be reached at TLC Eye Care of Michigan, 1116 W. Ganson St., Jackson, MI 49202; (517) 782-9436; fax: (517) 782-3001. Dr. Ernest has no direct financial interest in any of the products mentioned in this article. However, he is a paid consultant for Alcon.

Randall J. Olson, MD, can be reached at the University of Utah Medical Center, Department of Ophthalmology, 50 N. Medical Dr., Salt Lake City, UT 84158; (801) 585-6622; fax: (801) 581-3357. Dr. Olson has no direct financial interest in any of the products mentioned in this article. However, he is a paid consultant for Allergan.