Controlling PCO

An open capsule ring device (spacer) implanted through a standard intraocular lens (IOL) incision after crystalline lens removal and before IOL implantation has reduced posterior capsule opacification (PCO) by up to 88 per cent in an animal model, Guy Kleinmann MD told the 2016 ASCRS•ASOA Symposium & Congress in New Orleans, USA. It adds to evidence that opening the capsular bag may be more effective in preventing PCO than existing IOLs that rely on the capsule shrinking around a square edge to block lens epithelial cells (LECs) migrating across the posterior capsule. A recent publication by Menapace, describing long-term follow-up after cataract surgery, suggests that the new and modern hydrophobic square-edge IOL does not prevent PCO but delays it. The first to suggest an intracapsular ring for PCO prevention were Hara, followed by Nishi and Menapace. Prof Kleinmann, of Kaplan Medical Centre, Rehovot, Israel, and colleagues designed an open capsule device (spacer). Its vertical walls and square edge were designed to keep the anterior capsule open while allowing implantation of an IOL inside. At six weeks in an aggressive rabbit model comparable to three years in a human eye, this device reduced PCO by 68 per cent using histological analysis compared with eyes implanted with the same lens and no spacer. Eighty per cent reduced Soemmering’s ring formation, it has also been reported. (Alon et al. IVOS 2014;55:4005-4013) A second test compared three designs - one with square edges and apertures in the vertical walls to enable nutrient flow to the capsule wall, a second with square edges and no apertures, and a third with round edges and no apertures. These reduced PCO 43 per cent to 79 per cent on slit lamp examination, and 77 per cent to 100 per cent on histology compared with controls. Some cases of LEC protrusions were noticed, with the least at the square edge with the apertures design. A third study compared a square-edge design with different size apertures of high and low density. It also enhanced the posterior square edge with three sharp ridges as LEC barriers, and added an insertion platform that eases IOL implantation and modification of the inside groove that holds the IOL better in place. These reduced PCO 73 to 88 per cent at the slit lamp, and 73 to 100 per cent on histological analysis, with 74 to 78 per cent reduced Soemmering’s ring formation compared with controls, suggesting primary PCO prevention, Prof Kleinmann reported.

NUTRIENT FLOW

Holding the capsule open may reduce PCO in part by maintaining nutrient flow and TGF-β2 (minimising epithelial-to-mesenchymal transition) to remaining LECs, which prevents ischaemia and release of interlukin-1 that promotes cell proliferation, Prof Kleinmann said. By contrast, with traditional square-edge IOLs, cells proliferate between the sealed edges of the capsule leaves, eventually forcing them far enough apart to bypass the edge barrier. This may be why PCO increases three years after implantation, he said. “The intracapsular open capsule 
device reduced PCO by 70 to 88 per cent, and Soemmering’s rings by 74 to 80 per cent. We had better results with square edges and sidewall windows, but the ring material and the size and density 
of windows made no difference. We 
need much larger clinical studies to see the influence of the rings,” Prof Kleinmann concluded. Guy Kleinmann: 
guy.kleinmann@hsc.utah.edu

Tags: IOLs