The glaucomas are potentially treatable diseases, either by medication or surgery. Ab externo Er:YAG-laser sclerostomy, as an alternative surgical glaucoma therapy, produces a drainage canal from the anterior chamber into subconjunctival space. The procedure by itself did not achieve the desired success, as postoperative scarring of episcleral tissue often resulted in occlusion of the canal. The implant concept introduced in this study modifies the Er:YAG-lasersclerostomy procedure. The aim is to obtain an intact corneoscleral canal during the postoperative inflammatory period by implanting a non-draining stent into the canal as a placeholder. This should make for more favourable conditions for long-term functionality of the drainage canal after explantation of the stent. To avoid the necessary explantation procedure of the silicone stent, biodegradable plastics were tested for applicability as a possible stent-material, as the second part of this study.The silicone implant consists of a 300µm pim which bottoms out into a small flag. After conduction of the laser-sclerostomy the stent was implanted into four chinchilla-rabbits. Six weeks after implantation two animals were enucleated with stent in situ to evaluate the sclerostomy-morphology around the stent as well as subconjunctival reactions to the stent site. Two further animals underwent stent-explantation at the same time, enucleation was conducted 14 weeks after stent explantation. Bulbi were histologically processed. Analysis of the biodegradable glycolid-copolymers and of multiblockcopolymer oligo(p-dioxanon)diol, oligo(alkylen-glykoladipat)diol and diisocyanat (PDA) included processing, degradation in phosphate buffer, degradation in L929-conjunctival fibroblast culture, and biocompatibility testing for multiblockcopolymer PDA, consisting of EB/FDA vital staining, BrDU-, WST-1-elisa and cellmorphologic analysis of L929-fibroblasts.Surgical practicability of stent implantation was documented as well as high acceptance of subconjunctival tissue for the silicone stent. Histology showed fibrocellular connective tissue in the canal with the stent luxated from the canal. A pronounced fibrocellular sheathing was seen around the stent flag. The implant could not be found in one eye. Only minor inflammation was persistent 14 weeks after explantation, with fibrocellular occlusion of the canal. Iris incarceration occured in one eye after stent explantation without further complications.In the course of material analysis the glycolid-polymers turned out to be unemployable for stent construction due to missing elasticity and acidic degradation. Multiblockcopolymer PDA showed comparable results as biofilm-reference for all cytotoxicity testings. The results of degradation analysis were linear degradation without noticeable loss of elasticity and a less pronounced pH-value decrease.Modification of the lasersclerostomy-procedure by stent implantation could serve as a method to ameliorate postoperative conditions for a functioning drainage canal. The surgical procedure is easy to do and requires little complexity. Implantation of the non-degradable implant would be possible, following a concise explantation procedure in local anesthesia. Application and evaluation of the degradable PDA-stent in an animal model would be the next step, thus avoiding the traumatising explantation of the permanent silicone stent. The main aim is to avoid a remaining immunogenic foreign body in subconjunctival space. The labelled aspects should be subjects of further research
