Incidence of Conjunctival Exposure following Drainage Device Implantation in Patients with Glaucoma

Purpose To evaluate prior studies including a glaucoma drainage device and to describe the timing and incidence of conjunctival exposure. A meta-analysis of previously published articles. Methods Articles included were prospective, single cohort, or comparative parallel design, with a mean treatment period of at least 3 months and at least 30 patients per treatment arm. We limited our analysis to studies that evaluated the most common devices, including Ahmed, Baerveldt, and Molteno. Results We included 38 studies containing 45 treatment arms (16 Ahmed, 12 Baerveldt, and 17 Molteno). These studies included 3,105 patients and 3,255 eyes with an average follow-up of 26.1±3.3 months. The overall incidence of exposure was 2.0±2.6% (n=64) of eyes with an average exposure/month of 0.09±0.14%. There was no significant correlation between study length and incidence of exposure (p=0.11), although multivariate regression analysis identified length of follow-up as a risk factor for exposure (p=0.001). Among individual drainage devices, there was no significant difference in the incidence of exposure (p=0.22) or percent exposure per month (p=0.18). In addition, no difference existed in the incidence of exposure between sizes for the Baerveldt 250, 350 or 500 mm (p=0.7), number of plates for the Molteno Single or Double (p=0.3), nor between the composition of the Ahmed Silicone or Polypropylene (p=0.7). Conclusions This study suggests that tube exposure of glaucoma implants is unusual and the incidence does not differ between the Ahmed, Baerveldt, and Molteno implants. However, exposure appears to occur at any time within the first 5 years following implantation.