Insertion of sequential glaucoma drainage implant in a piggyback manner

Abstract

This pilot study, the first of its type, was conducted to determine the clinical outcome of a sequential glaucoma drainage implant (GDI) inserted in piggyback manner, that is into the bleb of a primary GDI. This was a retrospective chart study with a minimum 1-year follow-up involving 16 eyes of 14 uncontrolled glaucoma patients who had previously undergone sequential GDI performed using a technique to convert a one-plate into a two-plate implant system. Surgical success was defined as intraocular pressure (IOP) <21 mm Hg with at least a 30% reduction in IOP from baseline on two consecutive follow-up visits, IOP >5 mm Hg on two consecutive follow-up visits, and neither reoperation of glaucoma nor loss of light perception vision. The mean ±SD baseline IOP was 29.2±5.2 mm Hg, and the mean postoperative IOP was 17.3±3.4 mm Hg, with a mean pressure drop of 39.4±10.4% (P<0.001). Life-table analysis showed an 88% success rate after 12 months of follow-up. The mean preoperative best corrected visual acuity (BCVA) was 0.2±0.2 logMAR (Snellen equivalent 6/9.5), compared with 0.3±0.3 logMAR postoperatively (Snellen equivalent 6/12; P=0.497). Postoperative complications included a flat anterior chamber and choroidal detachment (one eye), uveitis and cataract (one eye), diplopia (one eye), and worsening of pre-existing pseudophakic bullous keratopathy (one eye). In glaucoma eyes with useful vision the piggyback GDI seems to provide a significant IOP lowering with minimal complications in patients in whom an initial GDI had failed to control the IOP.