Retrobulbar Shunt (RS) for Encapsulated Blebs

Abstract

 

Purpose

 

Loss of filtration with fibrotically encapsulated blebs has been a longstanding clinical dilemma, eventually affecting up to 20% of eyes undergoing traditional tube shunt procedures. In this series of eyes with encapsulated blebs refractory to other therapy a new wide-bore silicone secondary shunt resembling a “French drain” was implanted to deliver entrapped aqueous from the impervious bleb into the retrobulbar space. This study evaluates the efficacy of this new retrobulbar shunt (RS).

 

Methods

 

13 eyes with chronic bleb encapsulation and uncontrolled ocular hypertension underwent implantation of an RS silicone retrobulbar seton. The device was used in tandum with existing Ahmed or Baerveldt tube shunts. A unique arrowhead flange locked the implant into the bleb, further secured via tabbed eyelets, directing the tubing into the retrobulbar space. IOP and antiglaucoma medications were compared with pre-op levels 1 wk, 1 mo, 2 mo, 6 mo, 12 mo and 18 mo post-op (paired t-test).

 

Results

 

There were 5M/8F of mean age 61.5±2.9 yrs. Mean pre-op IOP was 31.5±2.8 mmHg on 2.7 ±0.4 medications. Mean IOP at the 6 post-op intervals was 10.9, 12.9, 13.3, 12.9, 14.0 and 16.5 (mean Δ-15.0 mm Hg (-48%); P=0.01), using 0, 0, 0.33, 0.18, 0.43 and 0.5 medications (mean Δ -2.2 meds (-81%); P=0.01). Viscoelastic reformations were required for several eyes post-op.

 

Conclusions

 

Encapsulated blebs have compromised glaucoma treatment for thousands of patients, a majority of whom were left with few effective alternative therapeutic options. With insertion of this retrobulbar shunt, the previously redundant bleb can be converted into a compressible cystern, resurrecting seton function by allowing transfer of aqueous into the retrobulbar space. Orbital fat acts as a one-way flow modulator for the multiple drainage ports in the large-bore RS silicone tubing. Since the original small-tubed ±valved shunt remains in situ, there is minimal risk of hypotony or hyphema. The high sulcus RS surgical insertion also minimizes risks of exposure or infection. Among these 13 eyes the RS was highly effective in substantially reducing IOP and medication requirement.

 

 

RS tube before implantation (above) and placed atop an Ahmed tube shunt in the orientation it would occupy in the eye (below). Note the large relative diameter of the RS tube.

 

 

RS in the bleb being sutured down before inserting posterior end into retrobulbar space.

 

Keywords: 568 intraocular pressure • 765 wound healing • 427 aqueous