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Jonathan D. Tung, Mauro T. Leite, Robert N. Weinreb, Linda M. Zangwill, Pamela A. Sample, Felipe A. Medeiros; Comparison Of The Rates Of Visual Field Loss Before And After Primary Trabeculectomy. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4409.
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To compare the rates of visual field loss before and after successful primary trabeculectomy.
This was a longitudinal observational study. All participants were recruited from the Diagnostic Innovations in Glaucoma Study (DIGS). To be included, patients had to have a minimum of 8 reliable visual fields (4 before and 4 after the surgery) and a follow-up of at least 4 years. All participants had open angles at presentation. Indications for trabeculectomy included evidence of progressive glaucomatous damage and/or uncontrolled intraocular pressure (IOP). Trabeculectomies were performed with mitomycin-C (69%), fluorouracil (21%), or neither (10%) at the discretion of the surgeon. Surgeries were considered successful if the mean post-operative IOP was at least 20% less compared to the mean pre-operative IOP. Rates of visual field loss before and after trabeculectomy were calculated using visual field mean deviation (MD) change over time. Linear mixed models were built to evaluate the effect of surgery on the rates of visual field loss over time. Estimates of the rates of change before and after surgery for individual eyes were obtained by best linear unbiased prediction (BLUP).
Twenty-nine eyes from 27 patients with successful trabeculectomy were included. The mean ± SD follow-up time was 11.2 ± 3.5 years (range 5 to 19 years). The average pre-operative IOP was significantly higher than the average post-operative IOP (20.8 ± 5.6 mmHg vs 9.0 ± 3.3 mmHg; P<0.001). The average IOP reduction was 11.8 mmHg ± 5.3 (range 3.2 mmHg to 22.6 mmHg). The rate of MD change before the procedure was -0.31 dB/year, significantly greater than the -0.05 dB/year after trabeculectomy (P=0.03).
Trabeculectomy resulting in at least a 20% reduction in IOP was effective in reducing the rates of visual field progression in our population.
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