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R. S. Ramchandran, R. R. Allingham, P. Challa, L. W. Herndon, T. Kim, P. J. Lee, E. A. Postel; Effectiveness of Pars Plana Tube Insertion for Refractory Glaucoma. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3962.
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To report the visual outcome and intraocular pressure control achieved after pars plana tube shunt implantation in eyes with refractory glaucoma.
Retrospective consecutive case series. The medical records of patients who underwent pars plana vitrectomy with concurrent implantation of a pars plana Ahmed S2 glaucoma tube shunt at the Duke University Eye Center from January 1, 1999 to December 31, 2004 were retrospectively reviewed. In total, 16 eyes of 16 patients were identified as having available data. Eight eyes had neovascular glaucoma (NVG) due to proliferative diabetic retinopathy or central retinal vein occlusion, 5 eyes had corneal decompensation, 2 eyes had uveitic-glaucoma-hyphema syndrome, and 1 eye had traumatic glaucoma. The primary outcome measures were visual acuity, intraocular pressure (IOP) recordings, and IOP lowering medication use at various time points over 24 months. The mean and median for each measure were calculated and Wilcoxon signed-rank tests were performed to determine the significance of the change in visual acuity, IOP, and IOP lowering medication use.
At 3 months post-implant, median best-corrected snellen visual acuity improved significantly from hand-motion vision to 20/400 (range hand-motion to 20/25) (p<0.02), and remained at or above this level through the 24th postoperative month. Postoperative IOP improvement included the following: IOP reduction from a median of 32 mmHg preoperatively to 20 mmHg on the first postoperative day (p<0.009), decrease in the median number of medications required from 3 postoperatively (range 0 to 4) to 1 (range 0 to 2) (p<0.001) at postoperative 1 week, decrease in the number of eyes requiring IOP lowering medication from 95% preoperatively to about 40% by the first postoperative week (P<0.005). Each of these improvements in IOP control continued through the postoperative 24th month. Surgery associated adverse events included a suprachoroidal hemorrhage in 1 eye, 5 eyes with tube blockage; 1 due to tube kink, 4 due to fibrin (relieved with intravitreal tissue plasminogen activator in 2).
This study reviews the outcomes of a valved implant, the Ahmed S2, which appears to have a similar effectiveness in preserving visual acuity, in complication rates, and in controlling IOP. Post-implant visual acuity was stable or improved in most eyes. However, given the risks associated with pars plana tube insertion combined with vitrectomy in these severely diseased eyes, a larger, prospective, study is needed to determine the efficacy and safety of this technique.
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