Sharp optic edge of IOL appears protective against PCO

August 15, 2005

Frankfurt, Germany—The design of the optic edge seems to be one of the most important factors in the development of posterior capsule opacification (PCO). IOLs with a sharp edge have less PCO regardless of the lens material, according to Thomas Kohnen, MD.

Dr. Kohnen, professor of ophthalmology, Johann Wolfgang Goethe-University, Frankfurt, Germany, and colleagues compared three IOLs: the CeeOn911A IOL (AMO; Pharmacia at the time of the study), which is made of high-refractive silicone and has a sharp anterior and posterior optic edge; the PhacoFlex IOL (Allergan) (SI40NB at the time of the study), which is made of high-refractive silicone and has a rounded optic edge; and the AcrySof MA60BM IOL (Alcon Laboratories), which is made of hydrophobic acrylic and has a sharp optic edge.

In an open, prospective, randomized, multicenter trial carried out in Germany, the investigators hypothesized both that the CeeOn911A IOL would be superior to the SI40NB IOL in preventing PCO and that the CeeOn911A edge would be equal to the MA60BM edge in preventing PCO, Dr. Kohnen explained.

Each of the seven study sites compared two of the IOLs intraindividually. Three centers studied silicone lenses and compared the sharp-edge optics with the rounded-edge optics. Four centers studied IOLs with sharp edges and compared the silicone IOLs with the hydrophobic acrylic IOLs. The development of PCO was evaluated by an independent examiner.

A total of 280 patients were enrolled, and 247 (494 eyes) patients had an IOL implanted: 108 patients had CeeOn and SI40NB and 139 patients had CeeOn and MA60BM. At the 3-year follow-up visit, almost 64% of the participants were available for evaluation. Patients were excluded if intraoperatively there was incomplete overlap of the anterior capsulorhexis over the optic-edge design.

The primary study outcome measurement was the accumulative incidence of YAG laser capsulotomy over 3 years. The secondary outcome was the measurement of PCO (total score and central 4-mm area of the optic) by the independent examiner.

Rate of YAG capsulotomy

The authors found that after 3 years when comparing the CeeOn911A IOL with the SI40NB IOL, five eyes (5.7%) that had the CeeOn911A IOL implanted underwent a YAG laser capsulotomy compared with 15 eyes (17%) that had the SI40NB IOL implanted.

This difference was statistically significant, he said.

"The PCO score for the total area of the IOL optic was statistically different for the SI40NB IOL, and the CeeOn911A IOL was found to be superior to SI40NB but not to the MA60BM IOL," Dr. Kohnen said. "We also found the same result for a 4-mm central area of the IOL."

In the eyes with the MA60BM IOL implanted compared with those with the CeeOn911A IOL implanted, the rate of YAG capsulotomies in both groups was 2.1%, which demonstrated the noninferiority of the CeeOn911A IOL, he said.

The investigators also found that the PCO scores for the total area of the IOL optic and for the central 4-mm area of the optic were similar for the two IOLs.

"The minimal PCO that we can achieve depends on the sharp optic-edge design. We have to include in our surgical intervention the intact IOL overlap of the anterior capsule rim. PCO prevention can be achieved with IOLs that have sharp-edged designs," he said.