To evaluate the impact of location of a silicone tube tip in the anterior chamber on corneal endothelium after Ahmed glaucoma valve implantation.

We measured the distance from the tip of a silicone tube in the anterior chamber to the posterior surface of the cornea by anterior segment optical coherence tomography (OCT) in 24 eyes of 21 patients who underwent Ahmed glaucoma valve implantation. All surgeries were performed by a single surgeon. The corneal endothelial cells of central, superior, superotemporal, and superonasal area of the cornea were examined by specular microscope before and after surgery.

The distance from the tip of the silicone tube in the anterior chamber to the posterior surface of the cornea and the corneal endothelium were measured at 19.2 ± 11.8 months (2.8-41.2 months) after surgery. At the central corneal area, a statistically significant decrease in the number of corneal endothelial cells (2278 ± 565/mm² vs. 2177 ± 529/mm² , p = 0.043) after surgery was observed, but no relationship was found between the amount of decrease and distance from the tip to the posterior surface of the cornea. At the superotemporal corneal area where the tip of the silicone tube was located in the anterior chamber, there was more significant loss of corneal endothelial cells than in the other areas after surgery ( p = 0.006). Moreover, the amount of endothelial cell loss at the superotemporal area was negatively correlated to the distance from the tip to the posterior surface of the cornea (partial correlation coefficient by time -0.558, p = 0.031).

To minimize the loss of corneal endothelial cells after Ahmed glaucoma valve implantation, ensuring a sufficient distance from the tip of the silicone tube to the posterior surface of the cornea is important.