Retrobulbar diversion of aqueous humor: clinical feasibility studies

The purpose of this study is to clinically evaluate a new form of glaucoma tube shunt drainage system. Tube shunts play an important role in management of advanced glaucoma, but eventually many blebs may become encapsulated and impervious to aqueous humor. This pilot study analyzed clinical efficacy of retrobulbar diversion of aqueous, either directly from anterior chamber (AC) or existing encapsulated blebs (EB), into the retrobulbar space (RS).

Nineteen patients with intractable glaucoma underwent retrobulbar fenestrated implant surgery (16 with EB-to-RS and 3 AC-to-RS). Intraocular pressure, glaucoma medications, and acuity were assessed relative to preoperative baseline values by paired t test preoperatively and bimonthly up to 2 years. Preoperative and postoperative values were compared by paired t test.

Surgical patients (7 male, 12 female; mean, 62±3.3 y; progressive study entry; mean follow-up, 18.2 mo) maintained substantial intraocular pressure reduction, from preoperative mean 33.1±2.0 mm Hg to a sustained bimonthly mean of 14.6±1.6 mm Hg (14.6±1.1, 16.4±1.7, 13.9±1.2, 13.0±1.1, 13.3±2.0, 14.0±1.1, 12.2±2.2, 13.9±2.0, 15.1±1.4, 17.6±1.6, 15.6±2.0, and 16.0±1.6 at months 2 to 24, respectively; all P<0.00001). Acuity remained stable. Glaucoma medications were reduced from 2.8±0.3 to a bimonthly mean of 0.56±0.26 medications through 24 months (P<0.0001).

Retrobulbar shunts can divert aqueous from the AC into the RS, overcoming (through secondary EB-RS) and potentially obviating (through primary AC-RS) the ocular hypertension resulting from fibrotic plate encapsulation.