Outcomes favorable for pars plana insertion of glaucoma drainage implant in eyes with penetrating keratoplasty

Key Points

Fort Lauderdale, FL-Glaucoma drainage implant (GDI) placement through the pars plana (PP) appears to be an effective method for controlling IOP in eyes with medically uncontrolled glaucoma that are undergoing penetrating keratoplasty (PK) or have an existing corneal graft, reported researchers here at the annual meeting of the Association for Research in Vision and Ophthalmology.

Investigators from the University of Virginia, Charlottesville, presented the results from a retrospective study of 51 patients (54 eyes) who had PP insertion of a 350 mm² valveless GDI (Baerveldt BG-102-350, Advanced Medical Optics) simultaneously with or after prior PK. During a mean follow-up of just more than 3 years, PK failure occurred in 21 eyes (39%), and IOP failure occurred in five eyes (9%) (IOP failure was defined as eyes with a final postoperative IOP 22 or 5 mm Hg, eyes that required further glaucoma surgery and eyes in which a devastating complication developed). Combined success was achieved in approximately 60% of eyes, in which graft survival and IOP control were maintained. Those outcomes were considered at least as good as those reported previously for eyes with a GDI placed in the anterior chamber, and the investigators suggested the graft survival results may even be slightly better in some cases.

"PP GDI insertion requires complete vitrectomy, takes more time than traditional anterior chamber placement, and also generally requires the efforts of a coordinated team comprised of cornea, retina, and glaucoma specialists. However, there are theoretical advantages for PP shunt placement in eyes with PK or an anticipated need for a corneal graft. By placing the tube through the pars plana, there is an avoidance of tube-cornea touch and also a minimizing of corneal exposure to backflow of inflammatory cells and mediators that may promote graft failure or rejection," said Matthew Witmer, MD.

Patients in the series had a mean age of about 70 years, included slightly more women than men (54% versus 46%), and were predominantly Caucasian (79%). Chronic angle-closure glaucoma was the most common glaucoma diagnosis (43%), followed by primary open-angle glaucoma (39%). Most eyes were pseudophakic (87%); the rest were aphakic.

Surgeries took place between 1996 and 2006 and were performed by a team of the same three surgeons, including a cornea specialist, a retina specialist, and a glaucoma specialist. Most of the eyes had undergone prior glaucoma surgery, including trabeculectomy, GDI placement, and argon laser trabeculoplasty. Some had also undergone up to three prior PK procedures.

About one-half of the eyes had simultaneous PK and PP GDI insertion, and many underwent other anterior chamber and posterior chamber procedures simultaneously. A retinal detachment occurred in one eye during surgery, but no other intraoperative complications occurred.

"The PP placement of the GDI is an especially attractive option for eyes that require other posterior segment procedures," Dr. Witmer said.

Results

Successful control of IOP was achieved in 88% of eyes at 12 months, and the success rate remained at 83% at 48 months. Nineteen eyes (35%) maintained IOP control without any glaucoma medications. Overall glaucoma medication use was reduced from an average of 3.2 medications preoperatively to 1.19 medications postoperatively.

A clear graft was maintained in 88% of eyes at 1 year and in 40% at 4 years. Analyses were conducted to determine factors associated with better graft survival. Simultaneous GDI-PK surgery, use of a temporary keratoprosthesis, and primary PK showed trends for better graft outcomes. A higher graft failure rate was seen in eyes with an anterior chamber IOL compared with eyes having either a posterior chamber IOL or aphakia. A diagnosis of chronic angle-closure glaucoma also was a significant risk factor for poor graft survival.

After surgery, all eyes received aggressive topical corticosteroid treatment. Through September 2000, the corticosteroid was tapered to discontinuation. Thereafter, patients were treated with a low-dose topical corticosteroid indefinitely.