Otago Glaucoma Surgery Outcome Study: Further Histology and Immunohistochemistry of Molteno Implant Blebs.

PURPOSE: To describe findings of light microscopic examination of Molteno implant bleb capsules. METHODS: Histological and immunohistochemical features of bleb capsules including distribution of apoptotic cells and cell fragments were examined in 11 eyes 0.2 to 30.4 years after Molteno implants. RESULTS: In the superficial layer of capsules, high proportions of cells showed cytological features of apoptosis, with a higher proportion of cells showing specific immunohistochemical features of apoptosis with a mean of 22% (range, 3%-40%) of cells staining positively for Fas ligand. This demonstrated that cells migrating into the superficial capsule were replaced over approximately 1 to 6 days. In the deeper layer a mean of 8% (range, 3%-38%) of apoptosing cells stained positively for Fas ligand. These lower proportions of positively staining cells and cell fragments in the deeper layers, and the presence of occasional positively staining cells on the inner surface of capsules, demonstrated continuous migration of cells into the deeper layers associated with breakdown of connective tissue matrix and the release of numerous membrane-bound vesicles. CONCLUSIONS: These findings demonstrated unexpectedly rapid turnover of cells in the superficial layer of the bleb capsule, where most cells were efficiently phagocytosed by nearby monocytic cells, macrophages, and histiocytes; the remaining cells migrating into the deeper layers completed apoptosis and disintegrated with release of collagenolytic enzymes and Fas ligand positive presumed "death messengers" that were carried toward the superficial layers by the aqueous.

Otago Glaucoma Surgery Outcome Study: cytology and immunohistochemistry of trabeculectomy blebs.

PURPOSE: To describe findings of light microscopic examination of trabeculectomy blebs. METHODS: Histologic and immunohistochemical features of blebs including cell types, and distribution of apoptotic cells and proapoptotic death messengers were examined in six eyes 6.0 to 25.9 years after trabeculectomy. RESULTS: All specimens showed a channel opening into a rectangular cleft in the middle layer of sclera. The channels showed degenerative changes with disintegration and loss of collagen fibers and few pyknotic cells. Changes were extensive on the upper surface of the cleft forming irregular channels extending through and around the edges of the superficial scleral flap into moderately cellular and vascular oedematous conjunctiva covered by intact epithelium. Immunohistochemical staining demonstrated migration of histiocytes from superficial blood vessels into the deeper layers where they apoptosed and disintegrated. Fas ligand+ proapoptotic death messengers were concentrated in the superficial conjunctival regions of blebs. CONCLUSIONS: These results indicated that the normal cell processes in functioning trabeculectomy blebs were similar to that of Molteno implant capsules. These processes involved migration of cells from superficial blood vessels into perivascular spaces and the deeper tissues where apoptosis occurred. Apoptosis was associated with breakdown of tissue matrix and release of proapoptotic death messengers that were transported by aqueous to the superficial layers where they suppressed collagen synthesis by inducing apoptosis in metabolically active cells.

Otago glaucoma surgery outcome study: electron microscopy of capsules around Molteno implants.

UNLABELLED: PURPOSE. To report the ultrastructure of cells and extracellular matrix components in Molteno implant capsules examined by scanning and transmission electron microscopy. METHODS: Ultrastructural features including cytology, distribution of apoptotic cells, collagens, basement membranes, elastic fibrils, and glycoproteins were examined by scanning and transmission electron microscopy. Findings were correlated with the clinical features of 31 specimens of glaucomatous eyes treated with Molteno implants 0.3 to 14.9 years previously. RESULTS: Capsules showed two layers: an outer, moderately cellular vascular layer of normal-appearing cells and collagen and an inner, avascular, hypocellular layer of altered cells and collagen. Cells included fibroblasts, myofibroblasts, and tissue histiocytes that showed features indicating metabolic activity, with swelling, vacuolation, and apoptosis, and the formation of numerous membrane-bound vesicles. These features, together with alteration and disintegration of extracellular matrix, increased with time after surgery. CONCLUSION: The results support those in previous light microscopic studies and indicate that the normal life cycle of capsules in both primary and secondary glaucoma include continual outer surface renewal balanced by inner surface degeneration associated with apoptosis and breakdown of tissue matrix components which become more marked over time.

Otago glaucoma surgery outcome study: tissue matrix breakdown by apoptotic cells in capsules surrounding molteno implants.

PURPOSE: To identify cell types and extracellular matrix components in Molteno implant capsules. METHODS: Histologic features including cytology, distribution of apoptotic cells, cytoantigens, collagens, basement membranes, elastic fibers, and glycoproteins were examined by light microscopy. Findings were correlated with the clinical features of 19 ocular specimens with glaucoma that had been treated with Molteno implants 11 days to 20 years previously. RESULTS: All but the earliest specimen capsules showed two layers: a moderately cellular outer layer of normally stained collagen and an inner avascular hypocellular layer of altered collagen. Capsules contained metabolically active fibroblasts and macrophages showing swelling, vacuolation, and apoptosis with localized loss of extracellular matrix in the inner layers of older capsules. Type I collagen was present in trace amounts. Collagens types III and VI and fibronectin were present in high concentrations in the capsules. Basement membrane material (collagen type IV and laminin) and thrombospondin were concentrated in the inner avascular layers. CONCLUSIONS: These results support previous findings that the normal capsule life cycle includes continual inner surface degeneration and external surface renewal. The cells and tissue matrix components of the outer capsule layer matched those involved in the initial phase of wound healing in vascular connective tissue. The tissue matrix components and widespread apoptosis found in the inner fibrodegenerative layer reflect scar tissue remodelling induced by exposure to the aqueous.

Otago glaucoma surgery outcome study: cytology and immunohistochemical staining of bleb capsules around Molteno implants.

PURPOSE: To describe the cytology and immunohistochemistry of Molteno implant capsules from cases of primary and secondary glaucoma. METHODS: Histologic features of capsules including cell cytology, the distribution of activated (proliferating) cells, apoptosing cells, and membrane bound vesicles (presumed death messengers) were assessed by light microscopy and correlated with clinicopathological features in 10 noninflamed eyes with good intraocular pressure control (nine autopsy and one enucleation) obtained from 2 months to 16.8 years after insertion of Molteno implants. RESULTS: All bleb capsules demonstrated two distinct layers. The thin external layer was cellular with fairly numerous small blood vessels coursing through normally staining, regularly arranged collagen fibers. The thicker, deeper layer was avascular, relatively acellular, and characterized by regularly arranged swollen and fragmented collagen fibers. Most cells in the external layer appeared normal; however, between 5% (in recently formed blebs) and approximately 50% (in well established blebs) showed cytological and/or immunohistochemical changes characteristic of metabolic activation and/or apoptosis. All cells in the deeper layer, regardless of time after surgery, also demonstrated cytological and/or immunohistochemical staining characteristic of metabolic activation and/or apoptosis. In addition, the deeper layer evidenced large numbers of minute membrane-bound vesicles (presumed death messengers). CONCLUSIONS: The balance between activation and apoptosis regulates the thickness and permeability of bleb capsules, and the normal lifecycle of bleb capsules includes continual inner surface degeneration and external surface renewal.

Otago Glaucoma Surgery Outcome Study: factors controlling capsule fibrosis around Molteno implants with histopathological correlation.

OBJECTIVE: To describe the histopathology of Molteno implant capsules in cases of primary and secondary glaucoma and to correlate them with surgical technique and clinical outcomes in quiet eyes. DESIGN: Human tissue study with clinicopathological correlation. MATERIALS: Seventy-five autopsy eyes or surgical pathology specimens obtained between 4 days and 23 years after insertion of Molteno implants were studied. Basic histologic features common to all bleb capsules were described, and the thickness was measured in 28 specimens from quiet eyes. MAIN OUTCOME MEASURES: Histologic features of capsules, including wall thickness, distribution of inflammatory cells, and presence or absence of fibrodegeneration, were assessed by light microscopy. RESULTS: Without aqueous flow (first stage of 2-stage insertion), the episcleral plates of Molteno implants were encapsulated by a very thin (20-60 micro m) avascular collagenous layer. The second stage of 2-stage insertion, with delayed drainage of aqueous and early temporary postoperative intraocular pressure (IOP) increase to 25 to 35 mmHg, produced thin (190-250 micro m) permeable capsules with fewer fibrovascular than fibrodegenerative components. Insertion of nonligatured implants with immediate aqueous flow produced thicker capsules (300-600 micro m) composed of an outer fibrovascular layer and an inner fibrodegenerative layer of approximately equal thickness. Three-stage insertion of modified Molteno implants with temporary externalization of aqueous flow onto the conjunctival surface and postoperative IOP not exceeding 12 mmHg produced the thickest (375-700 micro m) heavily fibrosed and impermeable capsules composed entirely of dense fibrovascular tissue without a fibrodegenerative layer. CONCLUSIONS: Capsules around functioning Molteno implants evolved through a series of histologic stages. Without aqueous flow, the episcleral plate of the implant stimulated encapsulation by a thin avascular collagenous layer. With aqueous flow, an immediate inflammatory reaction developed in the episcleral connective tissues that included collagenous and vascular components. After a variable delay, a fibrodegenerative process developed in the deeper layers of the capsule. The fibrodegenerative process may depend on sufficient increases of IOP for aqueous to displace interstitial tissue fluid from the deeper layers of the capsule. The final thickness and permeability of the capsule probably depend on the relative intensity and timing of these opposing processes, which were influenced by surgical technique and postoperative management.