Ultrastructural features of filtration blebs with different clinical appearances.

The authors studied two functioning filtration blebs to evaluate a possible transconjunctival route of aqueous humor flow and describe potential differences between thin cystic and thick opaque functioning filtration blebs. The specimens were prepared for light and electron microscopy immediately after surgical excision because of filtration bleb discomfort. Both blebs had normal collagen in the substantia propria. The collagen, however, was widely spaced and subepithelial connective tissue loosely arranged. Clear spaces were seen in the superficial substantia propria. Epithelial cells were focally acantholytic, separated by clear spaces. Consequently, clinically distinct blebs demonstrated similar histologic and ultrastructural features. The epithelial intercellular spaces observed in this study provide anatomic evidence that aqueous could move transconjunctivally as a mechanism for filtration bleb function.