Biocompatibility response to modified Baerveldt glaucoma drains

Purpose. The most common long-term complication of seton devices is failure of the filtering bleb 2 to 4 years after surgery due to occlusion by dense collagen scars. Thick fibrous capsules surround the site of the device, preventing drainage of fluid. Micromovement of the smooth drainage plate against the scleral surface may stimulate low-level activation of the wound healing response and lead to increased collagen scar formation and fibrous capsule thickness. Methods. To investigate this hypothesis, we modified 7 Baerveldt setons by adding porous cellular ingrowth material to the posterior surface of the drainage plate. Seven modified and 5 unmodified implants were implanted in the eyes of adult rabbits. After 6 months of implantation, analysis of the wound healing response and stability of the fibrous capsule surrounding the drainage plates of both modified and unmodified implants was performed. Light microscopy was used to measure the fibrous capsule thickness and to evaluate cellular morphology. Immunohistochemistry was used to image the relative numbers of macrophages and the amounts of type III and type I collagen present. Results. The fibrous capsules around the modified implants were significantly thinner and contained more type I collagen than type III collagen, compared with the capsules around the unmodified control plates (P=0.005). The numbers of macrophages within the fibrous capsule surrounding the modified plates were significantly lower than the numbers of cells in the capsules surrounding the controls (p=0.005). Conclusions. The results indicate that the fibrous capsules surrounding the modified implants were significantly more stable 6 months after implantation, compared with the capsules around the control, unmodified implants. Further long-term studies are needed to verify that the stability of the capsules around the modified implants persists over a period of years.

Duke Scholars

Author Stuart James McKinnon Ophthalmology, Glaucoma