Korean J Ophthalmol Vol.23, No.2, 2009 Table 1. Patient characteristics Characteristics Number of eyes/patients Age (mean±standard deviation) (years) Gender Female Male Diagnosis (eyes) Neovascular glaucoma Secondary glaucoma after vitrectomy Uveitic glaucoma Pseudophakic glaucoma Congenital glaucoma Primary open angle glaucoma Miscellaneous Previous glaucoma surgery (eyes) None One Two or more Value 95/90 54±15 28 62 50 (52.6%) 16 (16.8%) 9 (9.5%) 9 (9.5%) 3 (3.2%) 2 (2.1%) 6 (6.3%) 81 (85.3%) 11 (11.6%) 3 (3.2%) after AGV implant surgery. The lengths of the exposed Nylon strands were about 5 mm to prevent corneal irritation. If the IOP did not reduce immediately after surgery, the stents were removed earlier, either on the first postoperative day or at 1 week. Stents were usually removed on the first day when the postoperative IOP was about 25 mmHg or greater. If the postoperative IOP was about 30% less than the pre- operative IOP or less than 25 mmHg, stent removal was post- poned until 1 week postoperatively. We assessed surgical outcomes in terms of postoperative IOP and the incidence of complications. Complete success was defined as an IOP of ≤21 mmHg and ≥6 mmHg without additional glaucoma surgery and without anti-glaucoma medi- cation. Qualified success was defined as an IOP of ≤21 mmHg and ≥6 mmHg regardless of the use of anti-glaucoma medi- cation. Failure was defined as an IOP of >21 mmHg on maximally tolerated medication or <6 mmHg. Those who Fig. 2. The mean intraocular pressure (mean±standard deviation) after Ahmed glaucoma valve implantation. The hypertensive phase occurred between 2 weeks and 1 month postoperatively. Paired t tests were used to compare the mean intraocular pressures at differ- ent time points. 88 Table 2. Mean course of intraocular pressure and number of medications IOP (mean±SD) No. of Medications (mean±SD) Preoperative 37.1±9.7 3.2±1.0 First day 16.9±12.5 0.4±0.8 First week 14.5±8.4 0.6±0.9 Second week 20.7±8.6 1.0±1.0 First month 19.9±8.0 1.5±1.2 Second month 17.1±6.2 1.6±1.2 Sixth month 15.8±5.8 1.5±1.2 First year 15.2±5.6 1.4±1.3 IOP=intraocular pressure; SD=standard deviation. required additional glaucoma surgery, implant removal, or who had phthisis bulbi were also considered failures. Hypotony was defined as an IOP of <6 mmHg. The hypertensive phase (HP) was defined as that period when the IOP rose to >21 mmHg during the first 3 postoperative months following an IOP reduction to ≤21 mmHg.10 Resolution of the HP was evaluated by comparing IOPs and the number of medications needed between 6 to 8 months postoperatively and 1 month following the maximal IOP. Resolution of HP was defined as an IOP of ≤21 mmHg in conjunction with the following: a reduction of IOP by ≥3 mmHg on the same number of medi- cations or less, or a reduction in at least one medication associated with an IOP change of <3 mmHg.10 For comparisons between two normally distributed variables, we used paired t tests, and to compare paired non-normally distributed numeric variables we used the Wilcoxon signed rank test. Additionally, the cumulative probability of success was evaluated by Kaplan-Meier survival analysis during the follow-up period for more than 12 months postoperatively. IOP data are expressed as a mean and standard deviation. Two-tailed p values of <0.05 were considered statistically significant. Statistical analysis was conducted using SPSS for Windows (version 12.0, SPSS Inc., Chicago, IL). Results A total of 95 eyes (90 Korean patients) were included in this study. Table 1 summarizes the patient characteristics. The postoperative follow-up period was at least 12 months in each patient (mean follow-up period: 20.3 months). The most common indications for surgery were neovascular glaucoma (NVG) (52.6%) and secondary glaucoma after pars planar vitrectomy (16.8%). 81 eyes (85.3%) did not have any kind of glaucoma surgery before AGV implant surgery. These eyes had refractory glaucoma in which trabeculectomy with adjunctive anti-fibrotic therapy was expected to have a low chance of success in terms of IOP control.15 The mean preoperative IOP was 37.1±9.7 mmHg, and the mean postoperative IOP was 16.9±12.5 mmHg on the first postoperative day and 15.2±5.6 mmHg at 12 months (Fig 2,