Improving the Practicality and Safety of Artificial Corneas: Pre-assembly and Gamma Sterilization of the Boston Keratoprosthesis

Abstract

Purpose : Corneal blindness mainly affects non-developed countries where there is a lack of readiness for corneal transplantation. Most of those patients present severe corneal diseases associated to a high risk of rejection if a keratoplasty is performed. To overcome this, other treatments like the Boston Keratoprosthesis (KPro) can be applied. However, their access to KPro is limited because of the need of assembly to a donor cornea that acts as a carrier for grafting the combination. The shipping of pre-assembled KPro to a donor cornea could solve this issue. To achieve this goal, a sterilization process such as gamma irradiation (GI) should be applied to the combination of both elements. GI has been already safely applied to human donor corneas. However, the effect of GI to the KPro is unknown.

Methods : We have evaluated the effect of GI on 15mm-diameter discs of PMMA (the one used in the manufacturing of KPro) that were submitted to either ethylene oxide sterilization (the presently used process for KPro), or different doses of GI (10, 25 and 50 kGy), independently. Cell biocompatibility, mechanical strength and optical quality of the material were evaluated. Moreover, mechanical and optical evaluation of the actual KPro, before and after GI (25 kGy), was performed. The feasibility of assembling the KPro to an allograft and gamma-radiate afterwards was also evaluated.

Results : There were no differences in cell biocompatibility among the samples, after culturing corneal epithelial cells and fibroblasts in contact with them (p>0.05). The mechanical evaluation by statistical nanoindentation showed no alterations of the PMMA discs after GI. The optical evaluation showed high levels of transparency for the ethylene oxide, 10 and 25 kGy groups. The absorbance of ultraviolet was higher for the 25 and 50 kGy groups. This optical behavior was also observed for KPro after GI. The brittle test revealed a similar mechanical behavior of KPro before and after GI. Technically, pre-assembly and GI of the KPro revealed no problems.

Conclusions : Sterilization of KPro using GI has no detectable influence on the biocompatibility, mechanical or optical properties of the device. The pre-assembly of KPro to a donor cornea, followed by sterilization with GI, allowing long-term storage and easy shipment, emerges as an efficient and safe procedure.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.