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In refractory glaucoma, surgical intervention is required which in most cases aims at artificially increasing the drainage of aqueous humor from the eye. One surgical option used with increasing frequency is the implantation of episcleral glaucoma drainage devices (GDD). The clinical success of such devices is often limited by excessive wound healing and scar formation around the base plate of the implant. In severe cases, which seem to occur most frequently in pediatric patients, the rapid formation of a thick, water-impervious fibrotic capsule within months after initial implantation leads to diminished aqueous resorption and an increase in intraocular pressure to presurgical values. Often additional surgical interventions become necessary. Excision of the fibrotic tissue around the implant may help to salvage function and might be an alternative to the more commonly practiced implantation of an additional GDD. In the case series presented here the surgical method of capsular revision is described and the clinical outcome in 11 eyes from 10 patients is reported.

Epibulbar glaucoma drainage devices have been only slightly modified since their introduction more than 40 years ago. Having been used primarily in only difficult cases with a poor prognosis (and therefore with poor clinical results) the recently published trabeculectomy versus tube study (TVT) led to a change in our understanding of these devices. In this study epibulbar glaucoma drainage devices (here the Baerveldt device) were employed for early implantation (in some cases as primary glaucoma surgery intervention). Being sceptically monitored the results over the first 5 year clearly showed an almost equal or even better outcome in comparison to trabeculectomy. Despite these good results a critical evaluation seems mandatory mainly because of the unsolved problems concerning late complications. Late tube erosion with subsequent blebitis and enophthalmitis as well as late base plate encapsulation need to be mentioned here. The latter leads to thick fibrous tissue around the base plate resulting in an increase of intraocular pressure (IOP). Late corneal decompensation is also a late complication the pathomechanism of which is only poorly understood. Solving and treating such late complications are often troublesome and time consuming. Future experiments should lead to development of new drainage implant designs and the bulk material should be enhanced and optimized to increase clinical surgical 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.

Objective/aim: Uncontrolled glaucoma presents a challenge for the ophthalmic surgeon especially in children and juvenile patients. For many patients who have undergone failed surgical procedures before, episcleral implants remain the last choice. Encapsulated blebs forming over antiglaucoma devices present a complication leading to malfunctioning or even failure with reincrease in intraocular pressure. We report our histopathologic findings of such blebs developing around the Ahmed glaucoma valve (AGV) after a short time period in young patients., Materials and Methods: Nine young patients (2 to 17 y of age) with otherwise uncontrollable glaucoma were treated with AGV (models FP-7 and FP-8, silicone base plate) by 1 surgeon (H.T.). Four eyes needed surgical revision 2 to 6 months after initial implantation owing to encapsulated bleb development over the valve with total loss of function. The dense capsule around the device was surgically removed and investigated macroscopically, microscopically, and ultrastructurally., Results: The cystic wall of these encapsulated blebs had an overall thickness of 1.5 to 2 mm. Macroscopically, the tissue was split into 2 layers. Histopathologically, the smooth inner surface (facing the base plate of the AGV) consisted of compressed collagen fibers with signs of elastoid degeneration and with formation of a pseudoendothelium toward the base plate. There was a pronounced transformation of fibroblasts into myofibroblasts in this inner layer. The outer area was highly vascularized. In these vessels electron microscopy revealed thrombosis. Inflammatory responses were nearly absent in all areas of the excised material. Intraocular pressure could be controlled by removal of the encapsulated blebs in all 4 cases., Conclusions: Encapsulation of the AGV is an early complication in young patients, leading to inhibition of fluid exchange and failure of the procedure. The valve mechanism is blocked by contracted scar tissue, but the device itself is not affected by the encapsulation. Surgical excision of the capsule immediately leads to an aqueous flow and drop of intraocular pressure.

Purpose: This study was performed to investigate the surface topography of different glaucoma drainage devices and to determine the effects of surface roughness on cell adhesion of cultured human tenon fibroblasts., Methods: The surface topography of four widely used devices (Ahmed FP7 and Ahmed S-2; New World Medical, Inc., Rancho Cucamonga, CA; Baerveldt BG101-350; Advanced Medical Optics, Irvine, CA; and Molteno S1; Molteno Ophthalmic Ltd., Dunedin, New Zealand) was investigated by scanning electron microscopy, and roughness was quantified by white-light confocal microscopy. Cells were grown for 72 hours on the surfaces of implants affixed to standard culture dishes. The cells were labeled with a fluorescent dye and detected by confocal laser scanning microscopy, while simultaneously imaging the surface reflectance. Collagen adsorption was quantified immunologically by using fluorescent beads coupled to a secondary antibody., Results: The root-mean-square roughness was 1.5 +/- 0.1 microm (mean +/- SE) for the silicone Ahmed model FP7 and 1.3 +/- 0.1 microm for the Ahmed with polypropylene base plate Ahmed model S-2. The Baerveldt was substantially smoother, with a mean roughness of 0.1 +/- 0.01 microm. The Molteno was the smoothest of all devices (0.07 +/- 0.01 microm). Cell adhesion was most prevalent on base plates with higher surface roughness, markedly less pronounced on the smoother base plates, and independent of collagen adsorption., Conclusions: The most frequently implanted glaucoma drainage devices are of markedly different surface topography. Surface roughness appears to correlate with tenon fibroblast adhesion in vitro and also with the rate of occurrence of postimplantation hypertensive phase and failure due to fibrous encapsulation. Surface roughness may thus play a role in triggering excessive fibrovascular reactions. Smoother base plate surfaces may enhance the success rates of these devices.

Objective/aim: One of the factors limiting the long-term success of glaucoma drainage devices and traditional filtering surgery is the tendency of bleb encapsulation. Glaucoma shunts present an opportunity of introducing drug-eluting mechanisms for a lasting exposure of the bleb to anti-proliferative substances. The aim of this in vitro study was to investigate the effects of short- and long-term exposure of primary cultures of human Tenon's fibroblasts to different concentrations of paclitaxel on cell proliferation, migration, collagen production and cytotoxicity, in order to evaluate the suitability of the drug for the use in such a device., Materials/methods: Seven individual primary cultures of human Tenon's fibroblasts were observed over the course of 1 week after administering paclitaxel concentrations varying from 10(-9) mol/l to 10(-6) mol/l for either 1 hour or continuously. Relative cell count and migration across a cell-free area introduced by scratching through a confluent cell layer were determined every 24 hours, using photomicrographs of the cells for each concentration and exposure time. Soluble collagen concentration in the cell culture medium was determined using a Sircol collagen assay 72 hours after paclitaxel exposure. Cytotoxicity of the compound was assessed by flow cytometry using dual staining with annexin V-FITC and propidium iodide., Results: Paclitaxel dose-dependently inhibited both proliferation and migration of the cells. Cell count was reduced at all concentrations and both exposure times (p = 0.001); similarly, all but two concentrations of paclitaxel caused a significant reduction of cell migration (p < 0.001). This may be explained in part by the dose- and time-dependent induction of apoptosis in up to 23.7% of the cells (maximal effect at 10(-6) mol/l, 7 days after exposure). Collagen production was significantly reduced at all concentrations and at both exposure times. However, no statistically significant difference was observed between any of the concentrations, indicating that this inhibition may be an indirect effect., Conclusion: Paclitaxel may be a useful addition to the repertoire of anti-proliferative substances currently in use in glaucoma filtering surgery and shunt implantation. Further studies of the compound and its effects on Tenon's fibroblasts as well as other ocular tissues are warranted.