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Lower PCO may result from ‘wrapping’ capsule around
Lens material acts independently on lens cell migration.
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VIENNA, Austria — Overlapping the optic is paramount to prevent posterior capsule opacification (PCO), said Rupert Menapace, MD.
Dr. Menapace, of the University Eye Hospital in Vienna, reported his conclusions at the European Society of Cataract and Refractive Surgeons meeting.
“We all are aware that with the AcrySof lenses [Alcon, Fort Worth, Texas], a significantly lower rate of YAG capsulotomies and PCO has been observed,” he said. “But why is that so?”
It can be a function of the material and/or the design of the lens, he said. The adhesiveness of the material has been said to make the capsule adhere to the optic and prevent epithelial cells from growing behind the lens.
Material does not matter
Dr. Menapace assessed the posterior gap between the posterior capsule and lens with a slit lamp and a laser interferometer. Comparing different lenses showed that there was no significant difference between the AcrySof and other lens types with regard to both the frequency and the width of the posterior gap.
“If we look at those AcrySof cases that did not perform perfectly regarding PCO, we see that there is no capsulorrhexis/optic overlap and we can observe lens epithelial cell (LEC) ingrowth behind the optic,” he said.
Therefore, his hypothesis is that an overlap must exist in order to push the sharp optic edge against the posterior capsule, thus acting as a mechanical barrier to migrating LECs. Dr. Menapace, a member of the Vienna IOL Study Group, conducted a prospective, randomized, double-eyed, masked clinical trial to validate the theory.
Dr. Menapace conducted all surgeries. He did follow-ups at 3 months, 6 months, 1 year, 2 years and 3 years.
He measured visual function, conducted digitized retro-illumination photography and performed biomicroscopy. He compared the capsular bending/distance ring (CBR) to no ring, as well as sharp edge versus round edge PMMA lenses and sharp edge versus round edge silicone lenses otherwise identical in design and material.
Wrapping prevents PCO
From the study results, Dr. Menapace concluded that capsular bending and consecutive migration blockade is seen only when the anterior capsular leaf overlaps the anterior optic. Dr. Menapace saw this effect in both PMMA and silicone lenses.
The sharp implant performed better in preventing PCO, Dr. Menapace said. However, there also was a barrier effect with the round edge lens in cases with a wrapping of the posterior capsule around the optic edge. This seemed to result from the fibrotic contraction of the anterior capsular leaf.
“It is not the sharp edge per se but the capsular bend that is created by the optic edge that does not allow the cells to further migrate,” Dr. Menapace said. “Alternatively, such a bend also may be created at a round optic edge due to fibrotic capsular wrapping.”
For Your Information:
- Rupert Menapace, MD, practices at the University Eye Hospital, Waehringer Guertel 18-20, A-1090 Vienna, Austria; (43) 1-40400-7940; fax: (43) 1-40400-6630. Dr. Menapace has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.