Materials and Methods
The study protocol was approved by the institutional review board of Kim's Eye Hospital, Seoul, Korea. All participants provided informed consent before enrollment into the study and all procedures conformed to the guidelines set out in the Declaration of Helsinki. We reviewed medical records of the patients who underwent AGV implantation at Kim's Eye Hospital, Seoul, Korea, between June 2006 and December 2013. During this period, 714 patients underwent AGV implantation as the initial GDD implantation. Among them, secondary AGV implantation was performed in 23 eyes to treat inadequate IOP control after the first AGV implantation; all of these eyes were enrolled in the present study. A second AGV implantation had been performed on patients when the previous AGV implantation was considered to have failed, based on the following criterion: an IOP≥21 mm Hg on ≥2 consecutive follow-up visits, despite the use of IOP-lowering medications. For the other eyes with inadequate IOP control or complications such as corneal decompensation or vision loss after the initial AGV implantation, additional AGV implantation was not performed. For these eyes, depending on patient willingness and consent, either cyclodestructive procedures and trabeculectomy were additionally performed or no further surgery was attempted. Data collected included details of the surgical procedure and any intraoperative or postoperative complications. Data related to visual acuity (VA), IOP, and IOP-lowering medications at each follow-up were also recorded.
In all patients, an AGV was used as the GDD for both the initial and follow-up surgery. A single surgeon performed all operations. The surgical procedure used was the same for all patients, regardless of implant size. The type of AGV (FP8 model, 96 mm2 plate surface area or FP7 model, 184 mm2 plate surface area) was chosen by the surgeon according to the conjunctival status or size. An incision of the conjunctiva was made at the limbus. The AGV was inserted through the conjunctiva and Tenon's capsule, and then sutured to the sclera. The tube was trimmed to an appropriate length and then inserted into the anterior chamber, with the bevel facing anteriorly, through a corneoscleral track created using a 23 G needle. A quadrangular donor scleral patch graft was fashioned and then fixed over the exposed part of the tube using 10-0 nylon sutures. The conjunctiva and Tenon's capsule were repaired using absorbable sutures. The postoperative regimen included topical antibiotics and corticosteroids. The surgical methods and postoperative management used for the second AGV implantation were effectively the same as those used for the initial implantation surgery, apart from the choice of site. While the superior quadrants were generally selected for implantation in the initial surgery, various sites were chosen for the follow-up surgery: the site for implantation was selected on the basis of the patient's status, the AGV usually being placed in areas that had not undergone prior surgical procedures.
Surgical success was defined as an IOP maintained below 21 mm Hg, with a minimum overall reduction of 20% in the IOP, regardless of the number of IOP-lowering medications used. The criteria used to define failure were as follows: an IOP≥21 mm Hg or <5 mm Hg on ≥2 consecutive follow-up visits, the requirement for additional glaucoma surgery, or the loss of light perception. A Kaplan-Meier survival analysis was performed to assess success rates using the criteria defined above. A Cox proportional hazard regression analysis was used to determine predictive factors for failure. Statistical analysis was performed using SPSS version 12.0 (SPSS Inc., Chicago, IL).
J Glaucoma. 2016;25(6):e620-e624. © 2016 Lippincott Williams & Wilkins