Clinico-histopathologic correlation of a successful glaucoma pump-shunt implant

A 64-year-old diabetic man was treated for neovascular glaucoma with a pump-shunt implant (seton) after maximal medical therapy was unsuccessful. The seton, with supplemental agents, maintained the intraocular pressure (IOP) within a therapeutic range for 6 months, until the time of death from cardiac complications. Histopathologic evaluation of the eye showed the inlet of the seton in the periphery of the anterior chamber, not in contact with a coexisting anterior chamber intraocular lens (IOL). There was no fibrosis of the intracameral portion of the device. The tissue tract containing the silicon outlet tube extended from peripheral Descemet's membrane, through the sclera, to exit in the episcleral tissue over the posterior pars plana. Fibrous tissue originating from the episclera encased the external chambers of the seton. The internal contours of the fistulous tract, i.e., that portion adjacent to the seton, were smooth. There was no gross tissue hiatus at the exit port of the seton. The posterior wall of the fibrous capsule surrounding the seton in this region was diaphanous and immediately anterior to an area of cystic tissue comprising an equatorially placed bleb. The bleb was characterized by an irregular internal surface and a cystic cavity crossed by collagenous columns, suggesting it was the sub-Tenon's reservoir of aqueous. The success of the seton in this particular case may be due to a lack of fibrous reaction in the anterior chamber and the establishment of a stable filtering bleb in the equatorial region of the eye.