research digest

Silicone and Acrylic IOLs and PCO: Do We Have a Final Answer?

Since the current treatment of PCO carries risks and does not improve the visualization of the peripheral retina, surgeons are making every effort to prevent these risks by adopting new techniques to treat. According to Randall Olson, M.D., a large body of evidence exists showing that square posterior edged IOLs have lower PCO rates than those with rounded edges. Also, silicone IOLs appear to further lower PCO rates because of the creation of a strong barrier when an overlapping anterior capsule is present.

Joerg Schauersberger, M.D., and colleagues published a study in Journal of Cataract and Refractive Surgery in 2001 finding that 3 years after surgery, >40% of patients with acrylic IOLs showed symptoms of PCO, while >60% of patients with silicone IOLs showed no symptoms.

Giovanni Proscdocimo, M.D., and colleagues performed a study published in Journal of Cataract and Refractive Surgery in 2003 finding that the rate of PCO 18 months after surgery with acrylic IOLs was 0.365, while the rate with silicone IOLs was only 0.089 (P=.034).

Oliver Findl, M.D., and colleagues performed a a single-centered, prospective, randomized, patient- and examiner-masked, controlled trial compared the clinical outcome between an open-loop, sharp-edged, silicone three-piece IOL (CeeOn Edge 911A) and an open-loop, sharp-edged, acrylic 3-piece IOL (Acrysof MA60BM). The results of this trial were published in the January 2005 Issue of Ophthalmology.

The trial evaluated 106 eyes with age-related bilateral cataract. Patients were 78±4 years of age. Of the 106 eyes included in the study, 56 were available for all follow-up examinations.

Each patient had cataract surgery in both eyes and received a silicone IOL in one eye and a hydrophobic acrylic IOL in the fellow eye. Follow-up examinations were at 1 and 3 years after surgery. The amount of PCO was assessed subjectively at the slit lamp and objectively using automated image analysis software. Data of 56 eyes were examined at each follow-up.

At 1 and 3 years after surgery, PCO did not differ between the silicone (1.6 and 1.9, respectively) and acrylic IOLs (1.7 and 2.2) (P=.24). Furthermore, there was no significant difference in BCVA, IOL overlap, capsular folds and amount of anterior capsule opacification during the follow-up period. In each group, one YAG laser capsulotomy was performed.

In conclusion, this study showed that the materials silicone and hydrophobic acrylic were similarly effective in inhibiting PCO in the presence of a rectangular sharp optic edge. For hydrophobic materials, edge design seems to play a more important role in PCO inhibition than the optic material. It remains to be shown that this also holds true for hydrophilic acrylic materials.

Ophthalmology Management asked Dr. Olson to comment on the findings of this trial. He said that from these findings, "there is enough research/evidence to definitively say silicone IOLs don't cause PCO any more than acrylic IOLs." When asked to comment on the advantages of silicone IOLs, he said, "silicone IOLs actually cause less PCO when truncated."

Crystalens: 3-Year Follow-up Data

Follow-up data from the 3-year, prospective, multicenter trial of the crystalens IOL was released by eyeonics, inc. on March 7, 2005. The crystalens, which was designed to provide a continuous range of vision from distance through intermediate to near is indicated for adult patients undergoing cataract surgery who also desire correction of presbyopia. To date there have been more than 20,000 of these IOLs implanted worldwide.

The trial evaluated 497 eyes of 324 subjects: 143 males and 181 females. Patients enrolled had to be 50 years of age or older, scheduled for cataract surgery by phacoemulsifacation, a potential for BCVA 20/32 or better in each eye and a corneal cylinder of 1 D or less.

Three years following implantation with the crystalens, monocular near visual acuity of J3 or better measured through the distance correction was achieved by 92% of patients. Over 90% of patients are seeing 20/25 or better for bilateral uncorrected distance vision at 1 and 3 years. All patients (100%) showed no loss of accommodation with intermediate vision of J3 or better uncorrected-intermediate vision.

These results demonstrate that the improvement in the quality of patients' lives afforded by the crystalens is maintained as long as 3 years after implantation. Improvement in intermediate vision alone enables patients to perform tasks that they would otherwise not be able to do, such as view a computer screen.