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

PURPOSE To study the effect of glaucoma drainage implant (GDI) surgery on corneal topography during the first postoperative year. METHODS 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 12 months after surgery. Untreated opposite eyes served as controls. RESULTS 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 12 months 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 ± 46 μm, 535 ± 56 μm (p = 0.049) and 536 ± 45 μm (p = 0.080) at 0, 6 and 12 months, 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 12 months 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. CONCLUSION 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.