Bleb morphology characteristics and effect on positional intraocular pressure variation.

Background And Objective: To study bleb morphology and positional intraocular pressure (IOP) change (IOP supine to IOP sitting).

Patients And Methods: In this observational case series, blebs were graded for height, extent, vascularity, microcysts, and "ring of steel." Positional IOP change was analyzed using the paired t test. Associations between IOP change and bleb morphologies were evaluated by regression adjusting for inter-eye dependency.

Results: Ninety-five eyes of 68 subjects were included. Decreased bleb height (P = .05), absence of microcysts (P = .02), and increased bleb vascularity (P = .02) were associated with larger positional IOP change. Twenty patients with a filter in one eye and a medically treated fellow eye had larger positional IOP change in the medically treated eye (6.1 vs 4.6 mm Hg, respectively; P = .01).

Conclusion: Successful filtration surgery results in both lower IOP and less positional IOP change compared with medically treated eyes. Bleb features associated with smaller positional IOP change include higher elevation, microcysts, and less vascularity.