Serial intracameral visualization of the Ahmed glaucoma valve tube by anterior segment optical coherence tomography

Purpose To investigate serial changes of the Ahmed glaucoma valve (AGV) implant tube in the anterior chamber by anterior segment optical coherence tomography (AS-OCT). Methods Patients who had received AGV implantation without complications (n = 48) were included in this study. Each patient received follow-up examinations including AS-OCT at days 1 and 2, week 1, and months 1, 3, 6, and 12. Tube parameters were defined to measure its length and position. The intracameral length of the tube was from the tip of the bevel-edged tube to the sclerolimbal junction. The distance between the extremity of the tube and the anterior iris surface (T-I distance), and the angle between the tube and the posterior endothelial surface of the cornea (T-C angle) were defined. Factors that were related to tube parameters were analysed by multiple regression analysis. Results The mean change in tube length was -0.20 +/- 0.17mm, indicating that the tube length shortened from the initial inserted length. The mean T-I distance change was 0.11 +/- 0.07 mm and the mean T-C angle change was -6.7 +/- 5.6 degrees. Uveitic glaucoma and glaucoma following penetrating keratoplasty showed the most changes in tube parameters. By multiple regression analysis, diagnosis of glaucoma including uveitic glaucoma (P = 0.049) and glaucoma following penetrating keratoplasty (P = 0.008) were related to the change of intracameral tube length. Conclusions These results suggest that the length and position of the AGV tube changes after surgery. The change was prominent in uveitic glaucoma and glaucoma following penetrating keratoplasty. Eye (2012) 26, 1256-1262; doi:10.1038/eye.2012.131; published online 29 June 2012