Glaucoma filtration surgery using amniotic membrane transplantation

PURPOSE. TO investigate the potential use of amniotic membrane transplantat ion (AMT) in the construction of glaucoma filtering blebs. METHODS. Twenty-four albino rabbits underwent glaucoma filtration surgery i n one eye. In alternate cases, the conjunctival flap was replaced with AMT. Postoperative examination data were grouped into three time points. Six an imals with AMT and six filtration surgery-controls were euthanatized at eac h of two postoperative time points, and tissue was obtained for histologic examination. Conjunctival biopsies were explanted for estimation of fibrobl ast outgrowth. RESULTS. Bleb formation was observed in all eyes, and amniotic membranes we re epithelialized after 11.2 +/- 2.48 (mean +/- SD) days. Throughout the st udy IOPs were significantly lower in operated than unoperated fellow eyes. Between postoperative days 11 and 16 (the middle time point), the percentag e IOP reduction in AMT eyes was significantly greater than in filtration su rgery controls (P = 0.014), though not at other time points. Filtration sur gery survival was significantly longer in the AMT group (22.3 +/- 3.8 days; mean +/- SE) than in "No AMT" controls (14.0 +/- 1.6 days; P = 0.035). In tissue culture, significantly less fibroblast outgrowth occurred from AMT e xplants when compared with unoperated conjunctiva (P = 0.01) between postop erative days 3 and 9 (the early time point). Amniotic membrane transplants were intact on histologic examination after 14 days but were associated wit h considerable granulomatous inflammation. After 36 days, the ocular surfac es remained clinically intact, but lysis of AMT was noted histologically. CONCLUSIONS. AMT exhibits potential as an alternative tissue to conjunctiva in the construction of glaucoma filtration blt bs. The healing response as demonstrated by fibroblast outgrowth is retarded when compared with conven tional conjunctival closure. The improvement in bleb survival must be weigh ed against the potential for complications related to delayed heal-In rabbi ts, human amniotic membrane elicited a late xenograft reaction, leading to granulomatous inflammation and dis solution of the membrane.