Purpose
To describe one year clinical outcomes of patients undergoing pars plana tube shunt surgery with an Ahmed Glaucoma Implant (PP AGI).
Methods
Records of patients with a pars plana vitrectomy and aqueous tube shunt surgery at the Cole Eye Institute between 2001 and 2013 were retrospectively reviewed. Patients were identified by CPT codes for pars plana vitrectomy (67036) and aqueous shunt to extraocular reservoir (66180) or revision of shunt to extraocular resevoir (66185). Only those with an Ahmed Glaucoma Implant (model FP-7 or FP-8) were included in the study. Patients with less than one year follow up data were excluded. Data collected included demographics, pre and post operative visual acuity, intraocular pressure (IOP), number of medications, and complications. Statistical analysis was performed with Stata version 10. Changes in visual acuity were tested using the Wilcoxon signed rank test for matched samples. Differences in IOP were tested using the paired t-test. Differences in medications were tested using the student’s t-test. Risk factors for failure were assessed using univariate exact logistic regression.
Results
Complete data was available on 57 patients with an average follow up time of 38.5 months. Average age of patients was 64.1 years with a range from one to 88 years. OAG (43.9%), developmental (19.3%), and inflammatory/uveitic glaucoma (12.3%) were the leading diagnoses amongst those undergoing a PP AGI. One third of patients (29.8%) had previously undergone a glaucoma filtering procedure. Visual acuity stayed the same or improved in 73.7% (p=0.07). IOP was lowered from 31.2 mm Hg to 16.3 mm Hg (<0.001). A decrease in the number of medications from 2.9 preoperatively to 0.9 postoperatively was observed (p<0.001). The leading complication was corneal decompensation (14%). Two patients required subsequent glaucoma surgery. Two patients experienced a complication related to the posterior segment. There was no plate or tube erosion. Overall surgical success was defined as IOP between six and 21 on or off medications, no loss of light perception vision, and no further glaucoma surgical intervention. Success was achieved in 78.9% of patients (CI=66.1-88.6). Risk factors for failure were assessed but none were found to be statistically significant.
Conclusions
PP AGI surgery is a safe surgical option for complex glaucoma cases. Corneal decompensation remains a challenge, however, issues of plate or tube erosion are uncommon.