The Animal Research Of The PMMA-silicone Clamped Keratoprosthesis

Objective:To study the most suitable size of the central hole of the PMMA-silicone clamped keratoprosthesis back plate;To study the efficacy and complications of the bone-PMMA-silicone clamped keratoprosthesis implantation in the eyes of alkali-burned rabbit model;To explore the feasibility of the small incision PMMA-silicone clamped keratoprosthesis implantation.Methods:The experiment was carried out in three parts.Part Ⅰ:Alkali-burned rabbit models were established.Among them,twenty-four rabbits were divided into three groups:group A,group B and group C.Eight rabbits in each group were implanted PMMA-silicone clamped keratoprosthesis.The central aperture sizes of back plate were 2.0 mm in group A,2.5 mm in group B and 3.0 mm in group C.During the operations,the difficulties of keratoprosthesis assembly were compared;2 months after the operation to observe The tightnesses between the front and back plates of the keratoprostheses were observe during the 2 months postoperative period and the keratoprosthesis detachment rates were statistically analyzed.Part Ⅱ:Alkali-burned rabbit models were established.Among them,forty severely burned cases were divided into experimental group and control group,with 20 rabbits in each group.In the experimental group,the operation was divided into two stages:In stage 1 a small piece of rabbit scapula was resected,grinded into circular thin bone slice and embedded into the adjacent muscle pouch;during the same period,a cornea conjunctival autograft was performed.In stage 2,the embedded circular thin bone slice was taken out two months later and implanted between the conjunctival flap and the cornea to reinforce the cornea,and the PMMA-silicone clamped keratoprosthesis implantation was performed.In the control group,the bone slice was not added,and PMMA-siLicone clamped keratoprosthesis implantation was done alone.The postoperative effects and complications were observed within one year,and the incidence ofperforation in the experimental group and the control group was statistically analyzed.Part Ⅲ:Five alkali-burned rabbit models were established and implanted with PMMA-silicone clamped keratoprosthesis through a 7 mm main incision and two auxiliary incisions.the assembly of the front and back plates was performed inside the anterior chamber.The effects and complications were observed during operation and within 1 month after operation.Results:Part Ⅰ:During the observation period of 2 months,in group A,1 rabbit died of unknown causes,1 in the remaining 7 had keratoprosthesis detachment;in group By 1 had keratoprosthesis detachment,1 had high intraocular pressure;in group C,1 had keratoprosthesis detachment.There was no significant difference in the incidence of keratoprosthesis detachment between group A and group B(X2=0.010,P>0.05);there was significant differences in the incidences of keratoprosthesis detachment between group C and A,group C and B(X2=5.529,P=0.05;X2=6.349,P<0.05).The intraoperative procedures of keratoprosthesis assembly in group C were easiest,followed by that in group B,and that were most difficult in group A.Part Ⅱ:In the experimental group,1 case died ofanaesthesia accident intraoperatively.During the observation period of one year,2 cases died of unknown causes.Among the remaining 17 cases,2 cases had corneal perforation,2 cases had partial bone exposure(recovered after repairment),2 cases had glaucoma,1 case had posterior membrane formation,,and 15 cases maintained good anatomical positions without any other complications.In the control group,4 cases died of unknown causes during the one-year observation period.Among the remaining 16 casess 8 cases had corneal perforation,3 cases had glaucoma,3 cases had posterior membrane formation,1 case had infective endophthalmitis,and 8 cases maintained good anatomical positions without any other complications.Statistically,there was a significant difference in the incidence of corneal perforation between the experimental group and the control group(X2=5.705,P<0.05).Part Ⅲ:The procedure ofPMMA-silicone clamped keratoprosthesis were successfully performed through a 7-mm incision in 5 mild alkali-burned rabbit models.1 case had anterior chamber hemorrhage and no other intraoperative complications occurred.During the observation period of 1 month,1 case had glaucoma,and the other corneas remained transparent without any other complications.Conclusions:(1)The central hole of the back plate of the PMMA-silicone clamped keratoprosthesis should be about 1.0mm larger than that of the optical cylinder of the front plate.(2)The PMMA-silicone clamped keratoprosthesis is easy to be processed,easy to implant with low cost.Autologous corneal tissue is used as a keratoprosthesis holder,which saves precious allogenic corneal graft.The rabbit scapula is a simple and easy site for autogeoous bone extraction with thin bone plates.It is suitable for corneal reinforcement surgery.The scapular bone slice with the implaotation of the PMMA-silicone clamped keratoprosthesis increases the thickness of the cornea and has good safety and effectiveness.Its efficacy is better than that of single PMMA-silicone clamped implantation for severely burned corneas.(3)The PMMA-silicone clamped keratoprosthesis implantation can be done through a 7mm small incision.Small incision PMMA-silicone clamped implantation is a relatively safe and effective way of implantation.It is worthy of further research and application.