Korean J Ophthalmol Vol.23, No.2, 2009 Fig. 4. Cumulative probability of success over time, based on Kaplan Meier survival analysis. Cumulative probability at 12 months was 84.2%. definition given above. In 25 eyes (26.3%), the occurrence of the HP could not be ascertained definitely due to the use of medications, despite an IOP of 21 mmHg or less. The HP appeared after an average time of 2.7±1.5 weeks. The highest IOP in these eyes with a HP ranged from 22 to 48 mmHg, with a mean of 29.8±6.9 mmHg. HP resolution occurred in 38 of the 49 eyes (77.6%), according to the study definition. In most patients that experienced a HP, the IOP was controlled by additional medication. Needling of the bleb was done in 2 eyes, and a second implant was required in three. Complications occurred in 33 (34.7%) of 95 eyes after AGV implantation (Table 4). Eight eyes (8.4%) had more than one complication. Complications during the early postopera- tive period (within 3 months of AGV surgery) were hyphema, postoperative hypotony, a shallow anterior chamber, tube occlusion, and choroidal effusion. Late hypotony, phthisis, exotropia, plate exposure, bullous keratopathy, and corneal opacity were later complications and were encountered after 3 months postoperatively. The most common complication was hyphema in 17 eyes (17.9%). 88.2% (15 eyes) of these hyphema cases occurred in patients with NVG. Six eyes (6.3%) showed a shallow anterior chamber on the first postoperative day. The mean IOP of these 6 eyes was 9.5 mmHg, and one eye had hypotony. Suprachoroidal hemorrhage did not occur. Choroidal effusion occurred in one eye with congenital glaucoma and an IOP of Table 5. Visual acuity after AGV implant surgery Visual acuity ≥ 20/40 ≥ 20/200 ≥ Counting fingers Hand motion Light perception No light perception 90 6 mmHg, and was treated with oral prednisolone. Tube occlu- sion was observed in two eyes. These were caused by a blood clot and a vitreous strand in two pseudophakic glaucoma patients. A Nd:YAG laser was used on the tube occluded with the vitreous strand due to a high IOP. Late hypotony occurred 6 months postoperatively and lasted for more than 3 months in 2 eyes (2.1%). These eyes had shown a normal range of IOPs before the development of late hypotony, without a history of early postoperative hypotony. Phthisis occurred in 3 eyes (3.2%). All 3 of these eyes were diagnosed as NVG preoperatively. At the time of AGV implan- tation, 1 eye had had a chronic total retinal detachment with no treatment, and 1 eye had undergone vitrectomy because of total retinal detachment. The AGV was removed due to plate exposure in one eye, but the IOP after AGV removal was within the normal range with tolerable medication. Visual acuity was within one line in 55 eyes (57.9%) but had worsened two lines or more in 17 eyes (17.9%) at 1 year after surgery. Seven eyes (7.4%) that had NVG and poor vision before surgery, ranging from counting fingers at 30 cm to light perception, lost light perception during the current study. In the present study, AGV implantations were performed in 16 eyes (16.8%) with no light perception. The purpose of the operation in these patients was to control pain and maintain the eyeball by lowering the IOP (Table 5). In this study, 15 eyes (15.8%) were considered failures. 6 eyes (6.3%) had more than 21 mmHg with medication. An additional drainage device was implanted in 3 of these eyes (3.2%). Five of the 15 eyes (5.3%) failed because of hypotony and phthisis, and the implant was removed from the remaining eye (1.0%) due to plate exposure. Based on our criteria for success, complete success was achieved in 28 eyes (29.5%), and qualified success in 80 eyes (84.2%) at 1 year. Kaplan-Meier survival analysis showed a cumulative probability of success of 84.2% after 12 months (Fig. 4). D iscussion Early postoperative hypotony and its attendant complica- tions, including choroidal detachment and suprachoroidal hemorrhage, still continue to present a clinical problem in valved glaucoma implants. The incidences of early postope- rative hypotony in AGV implant surgery range from 8% to 13% using an intraocular pressure definition of <5 mmHg or Before surgery No. of eyes (%) 1 year after surgery No. of eyes (%) 3 (3.2%) 5 (5.3%) 33 (34.7%) 31 (32.6%) 7 (7.4%) 16 (16.8%) 8 (8.4%) 16 (16.8%) 21 (22.1%) 24 (25.3%) 3 (3.2%) 23 (24.2%)