HISTOLOGIC EVALUATION DURING HEALING OF HYDROGEL CORE-AND-SKIRT KERATOPROSTHESES IN THE RABBIT EYE

Purpose. We developed two models that are modifications of our origina l poly(2-hydroxyethyl methacrylate) (PHEMA) core-and-skirt keratoprost hesis. In these keratoprostheses, the mechanical strength of the skirt has been considerably increased with divinyl glycol (DVG) as a cross- linking agent during polymerization. In one (KPro I), methyl methacryl ate (MMA) was added as comonomer to increase cell adhesion, and in the other (KPro II), HEMA was polymerized with DVG without comonomer. The aim of this study was to evaluate the process of healing and biocolon ization and to ascertain whether KPro I demonstrates better ingrowth t han the mechanically stronger KPro II, after implantation in rabbit ey es. Methods. Ten rabbits were used for each model and studied at five predetermined end points up to 26 weeks. The device was implanted as a full-thickness keratoprosthesis covered with a conjunctival flap. Res ults, Neither prosthesis demonstrated extrusion or retroprosthetic mem brane formation. There was no significant difference between the two t ypes of prosthesis with respect to tissue ingrowth and surrounding tis sue melting. Histologically, inflammation was not severe, but calcific ation was seen in most specimens. Evidence of biodegradation of the pr osthesis also was seen. Conclusion, In our original keratoprosthesis, fibrovascular invasion had occurred into the prosthetic skirt, but wou nd dehiscence and low mechanical strength resulted in an unfavorable o utcome. In this series, the mechanical properties were improved, and K Pro II was stronger than KPro I. Therefore KPro II would be the prefer red polymer combination for surgical manipulation. However, biodegrada tion and calcification require further investigation into the degree a nd significance of these adverse reactions.