[Pathophysiology of fibrotic encapsulation of episcleral glaucoma drainage implants: modification for improvement of clinical results].

Episcleral glaucoma drainage implants (GDI) are being used increasingly more as a surgical option for lowering intraocular pressure (IOP). One of the main reasons for failure to control IOP is the formation of water-impervious fibrotic tissue around the base plate of GDIs that prevents effective resorption of the drained aqueous humor and thus leads to an increase in IOP. Surgical removal of the fibrotic tissue can often rescue implant function; however, repeated encapsulation can often not be prevented and necessitates additional interventions up to the removal of the implant itself. The reasons for the fibrotic reaction are not fully understood. Apart from patient-dependent mechanisms that are also involved in bleb scarring after trabeculectomy, implant properties, such as size, shape, surface properties and biomaterial probably contribute to the encapsulation process. Based on the literature on this topic this article looks at possible ways of improving the design of currently used drainage implants including the potential use of GDIs as a carrier for antifibrotic medication released at low doses over an extended period of time.