Ultrastructural Changes in Regenerated Tissue Around a Polyvinylpyrrolidone Hydrogel Accommodative Intraocular Lens during Long-term Observation

Abstract

Purpose: In previous studies we implanted a polyvinylpyrrolidone (PVP) hydrogel intraocular lens (IOL) into the capsular bag of the rabbit eye and reported that posterior capsule opacification (PCO) had changed from opacified to transparent by 12 months postoperatively, and that the structure of regenerated tissue around the PVP hydrogel IOL had degenerated by 6 months (see ARVO 2012). In this study, we examined the regenerated tissue at 12 months to further elucidate changes in PCO.

Methods: PVP hydrogel IOLs were implanted into the capsular bags of Japanese white rabbits. Phacoemulsification only was performed in control eyes to form an empty capsule. Slitlamp examination was performed monthly for 12 months postoperatively. The eyes were enucleated at 12 months postoperatively and the anterior segments were examined histologically by light and transmission electron microscopy.

Results: Slitlamp examination: In the control eye, PCO developed and the posterior capsule had become opacified by 12 months. In contrast, in the implanted eye, PCO developed but had regressed by 12 months. Light microscopy: Although a monolayer of lens epithelial cells (LECs) along the anterior capsule and regeneration of the lens cortex were found in the control eye, only thin layers of cells were observed between the PVP hydrogel IOL and posterior capsule in the implanted eye. Transmission electron microscopy: In the regenerated tissue of the control eye, LECs appeared to have normal cell organelle, and cell junctions were present. However, some bladder cells were observed along the posterior capsule. In the implanted eye, LECs and lens cortex were not observed, and fiber-like structures and degenerated cells were present at the periphery of the posterior capsule. Furthermore, compared to the tissue regenerated around the PVP hydrogel at 6 months postoperatively, the numbers of organelles and granules were lower and the arrangement of the fiber-like structure had become regular.

Conclusions: Regenerated tissue around the PVP hydrogel IOL gradually became regular, and although PCO developed, the posterior capsule was transparent by 12 months postoperatively. However, in the empty capsule, PCO developed and remained at 12 months. These results suggest that the PVP hydrogel IOL may contribute to the atrophic changes of PCO.

Keywords: 652 posterior capsular opacification (PCO) • 567 intraocular lens • 404 accommodation