superior versus inferior ahmed glaucoma valve implantation

purpose: to compare the efficacy and safety of ahmed glaucoma valve (agv) implantation in the superior versus inferior quadrants. methods: this prospective parallel cohort study was performed on 106 eyes of 106 patients with refractory glaucoma. main outcome measures included intraocular pressure (iop) and rate of complications. other outcome measures included best-corrected visual acuity (bcva), number of glaucoma medications and success rate (defined as at least 30% iop reduction and 5 results: agv was implanted in the superior quadrants in 58 eyes and in the inferior quadrants in 48 eyes. baseline characteristics were comparable in the study groups, except for preoperative iop which was higher in the superior group (p=0.01). patients were followed for a mean period of 10.6±8.5 and 10.6±6.8 months in the superior and inferior groups, respectively (p=0.48). bcva was comparable between the groups at all postoperative visits. after one year, statistically significant but comparable iop reduction from baseline (p<0.001) was achieved in both groups (47.0±27.2% and 43.0±24.5% reduction for the superior and inferior groups respectively, p=0.725). mean number of glaucoma medications was comparable after one year (1.3±1.2 versus 1.9±0.8 for superior and inferior implants respectively, p=0.256). success rates were also similar after one year: 27 eyes (81.8%) versus 20 eyes (95.2%) for superior and inferior implants, respectively (p=0.227). however, the overall rate of complications such as implant exposure necessitating removal, cosmetically unappealing appearance and endophthalmitis was higher in the inferior group: 25% versus 5.2% (p=0.004). conclusions: superior and inferior agv implants have comparable intermediate efficacy in terms of iop reduction, decrease in number of glaucoma medications and preservation of vision. however, the inferior quadrants entail significantly more complications. it may be prudent to avoid agv implantation in the inferior quadrants if the superior quadrants have no contraindications to surgery.