Effect of Lens Status on the Outcomes of Glaucoma Drainage Device Implantation

OBJECTIVE:To assess the effect of lens status and cataract surgery on glaucoma drainage device (GDD) efficacy. DESIGN:Retrospective cohort study. SUBJECTS:243 eyes of 216 patients that underwent GDD implantation with ≥ one follow-up visit within 3-years postoperatively. Exclusion criteria included GDD combined with other ophthalmic procedures. 90-94% of GDDs were Ahmed implants; 83-90% had adjunctive mitomycin-C. METHODS:Outcomes were compared between phakic eyes (group A), eyes phakic at time of implantation but subsequently underwent cataract surgery within three years (group B), and pseudophakic eyes (group C). Outcomes were measured at 1, 3, 6, 12, 24, and 36 months after tube shunt implantation. Multivariable regression models were performed, adjusting for baseline characteristics. MAIN OUTCOME MEASURES:Intraocular pressure (IOP) after GDD implantation. Secondary outcomes included change in visual acuity (VA), number of glaucoma eye drops, and rate of failure, defined as additional glaucoma surgery, vision decrease to no light perception, or IOP persistently ≤ 5 mmHg or > 21 mmHg or not reduced from baseline by 20%. RESULTS:There were 65 eyes in group A, 52 in group B, and 126 in group C. Within group B, cataract surgery was performed a mean of 1.3±0.7 years after GDD implantation. There were no statistically significant differences in mean IOP or medications between the three groups at all time points up to three years postoperatively. Significant improvement in VA was noted in groups A and B compared to group C at six months, one year, and two years after implantation; however, by post-operative year three, change in VA was similar across groups. There were no significant differences in the failure rate amongst groups (p=0.68). IOP and medications up to 12 months after cataract surgery were similar compared to preoperative baseline. Group B had significantly more short-term (p=0.02) and long-term (p<0.001) postoperative complications than groups A or C, driven primarily by hypotony. CONCLUSIONS:There were no differences in IOP, glaucoma medications, or rate of failure three years after GDD implantation based on lens status or after undergoing subsequent cataract surgery. These results may inform the management of patients with co-existing glaucoma and cataract.