Effect of glaucoma drainage implant surgery on corneal topography: a prospective study.

Abstract

To study the effect of glaucoma drainage implant (GDI) surgery on corneal topography during the first postoperative year. Twenty-one adult glaucoma patients were implanted with a Molteno3 or a Baerveldt 250 GDI. Corneal topography measurements were taken preoperatively and at 6 and 12months after surgery. Untreated opposite eyes served as controls. In the surgical group, the mean±SD simulated average keratometry values were 44.36±1.69 D, 44.08±1.29 D (p=0.266) and 44.15±1.32 D (p=0.554) before and 6 and 12months after surgery, respectively. The corresponding simulated keratometry astigmatism values were 1.11±1.11 D, 1.20±1.01 D (p=0.687) and 1.16±0.71 D (p=0.177). Posterior astigmatism and posterior average keratometry remained unchanged after GDI surgery as well. The mean±SD central corneal thickness (CCT) was 530±46μm, 535±56μm (p=0.049) and 536±45μm (p=0.080) at 0, 6 and 12months, respectively. A trend towards increased corneal thickness (CT) in response to GDI surgery was also seen in both the average peripheral and the tube-quadrant peripheral CT values. At 12months postoperatively, the mean endothelial cell density (ECD) had decreased by 8% centrally and by 9% peripherally. Corneal topography parameters, CT and ECD did not significantly change in the control group during follow-up. Glaucoma drainage implant (GDI) surgery did not significantly alter corneal keratometry parameters and thus seems to be an astigmatically neutral procedure. However a slight, although seemingly transient, increase in CCT was observed after GDI implantation.