AIM:To assess the efficacy and safety of improved glaucoma drainage valve implantation in the treatment of refractory glaucoma after vitrectomy.

METHODS: The improved procedure: the surgeon used a crescent knife to make a scleral sleeve with a width of about 2mm and a length of about 3mm behind the limbus 5mm to 7mm; maked a length of about 1.5mm scleral tunnel at a distance of 3.5mm from the limbus; piercing the posterior chamber by a one-time spear knife through the scleral tunnel; the drainage tube was trimmed to the proper length, then placed between the iris and intraocular lens in the posterior chamber through the scleral sleeve and scleral tunnel. Reduce the pupil, we could see the drainage tube port in the pupil margin, drainage tube mouth beveled toward the pupil edge. All patients underwent modified surgical glaucoma drainage valve implantation. Patients incorporated into the study who had secondary glaucoma after vitrectomy and intraocular lens implantation admitted to our hospital from March 2016 to August 2017. Follow-up time: 1, 3d, 1wk, 1 and 6mo, followed up every 6mo. The intraocular pressure, intraoperative and postoperative complications and related treatment methods were analyzed before and after surgery. Intraocular pressure(IOP)at different time points before and after surgery was compared using repeated measures of variance analysis.

RESULTS: A total of 26 patients were enrolled in the study. The average IOP was 42.5±8.1 mmHg preoperatively, 12.1±11.2mmHg on the first day after surgery, 14.3±5.9mmHg in the last follow-up. There was a statistically significant difference between preoperative IOP and that on the first postoperative day(P<0.001). There was no significant difference in intraocular pressure between the first day after surgery and the last follow-up(P=0.89). There were 8 eyes with IOP less than 6mmHg on the first postoperative day. There were 6 eyes with IOP higher than 6mmHg on the first postoperative day, then dropped below 6mmHg on the third postoperative day. The rate of early postoperative low intraocular pressure was 54%. IOP returned to normal after intravitreal injection of air, injection of drug(triamcinolone acetonide), or injection of viscoelastic into the anterior chamber. During the follow-up no corneal endothelial decompensation, drainage tube exposure, explosive choroidal hemorrhage, endophthalmitis and other serious complications.

CONCLUSION: Improved glaucoma drainage valve implantation is a safe, effective and less-complicated surgical procedure for the treatment of refractory glaucoma. Anterior chamber injection of viscoelastic, vitreous cavity gas injection is a simple, effective, repeatable, and easy-to-use method for the treatment of early hypotony after glaucoma valve implantation.