A Long-term Implant Test of Poly(vinylpyrrolidone) Hydrogel in Rabbits: Potential as an Accommodative Intraocular Lens

Abstract

Purpose:: Poly(vinylpyrrolidone) (PVP) hydrogel is a hydrophilic material that has a similar property of the crystalline lens in the aqueous humor. In a previous study, PVP hydrogel implanted into the capsular bag of rabbit eyes for 4 weeks successfully filled the capsular bag and maintained their clarity and elasticity. This is a report of long-term observations of rabbit eyes.

Methods:: Female Japanese White rabbits weighting 2.0 to 2.5 kg were used. Endocapsular phacoemulsification was performed and the PVP hydrogel was implanted into the capsular bag. Slitlamp examination was performed once every month for 7 months postoperatively, and fundus examination at 7 months postoperatively. The anterior chamber depth was measured with a Schimpflug camera to determine the accommodative amplitude as the difference of anterior chamber depth before and after mydriatic eyedrops. The eyes were enucleated at 7 months postoperatively and resin-embedded sections (Hematoxylin and Eosin stain, 3-µm) of the anterior segments were prepared for histological examination. Liquid chromatography mass spectrometry (LC-MS) was performed to detect any PVP hydrogel-derived substances in aqueous humor.

Results:: Slitlamp examination revealed no inflammatory reaction or corneal opacification for 7 months. Although the Schimpflug camera confirmed the presence of the PVP hydrogel in the capsule bag, it did not allow determining the accommodative amplitude. Posterior capsule opacification (PCO) was observed and the fundus was invisible because of thick cell layers. Histopathological examination showed 1.5-mm-thick cell layers present between the PVP hydrogel and posterior capsule. Anterior capsule opacification was, however, very mild, and the cells that proliferated into the posterior capsule could not migrate to the anterior capsule because the edge of the PVP hydrogel prevented the migration. LC-MS confirmed that no PVP hydrogel-derived substances were present in aqueous humor.

Conclusions:: These results suggest that PVP hydrogel is a biocompatible material suitable for accommodative IOL. The Schimpflug camera allowed non-invasive observation of the PVP hydrogel in the capsule bag. Further study is necessary to improve the shape of the PVP hydrogel in preventing the PCO, and to develop a technique to determine accommodative amplitudes.

Keywords: crystallins • intraocular lens • anterior chamber