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

To describe findings of light microscopic examination of Molteno implant bleb capsules.

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.

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.

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.