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M. Singh, T. Aung, T. A. Tun, C. Zheng, P. T. K. Chew; Quantitative Analysis of the Change in Bleb Morphology Over Time After Successful Trabeculectomy. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3370.
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To measure the change in bleb morphology over 6 months after successful trabeculectomy, using anterior segment optical coherence tomography (ASOCT).
In this IRB-approved prospective longitudinal case series we included eyes with glaucoma that had undergone standardized fornix-based trabeculectomy with mitomycin-C augmentation from September 2006 - June 2007, and had successful outcome. Success was defined as postoperative intraocular pressure (IOP) ≤ 18mmHg without ocular hypotensive medication (if preoperative IOP > 18mmHg with or without medication) or IOP reduction of more than 20% (if preoperative IOP ≤ 18mmHg without medication), 6 months after trabeculectomy. Blebs were imaged at 1 week, 3 months and 6 months after surgery using ASOCT (Visante OCT prototype, Carl Zeiss Meditec Inc., Dublin, CA, USA), obtaining a single radial line scan through the site of maximal bleb elevation. Total bleb height (hB), bleb cavity height (hC), cross sectional area of the bleb cavity (AC), cross sectional area of the bleb wall (AW) and total cross sectional area of the entire bleb (AB) in each image were calculated using custom software. Statistical significance was determined using the paired t-test.
70 eyes were included with a mean follow up of 6.6 ± 1.5 months. The mean age of patients was 66.2 ± 9.0 years. Mean preoperative IOP was 17.6 ± 5.2 mm Hg with a mean of 1.8 ± 1.0 medications. Mean IOP at 6 months was 12.4 ± 3.3 mmHg with no medications. Mean hB increased from 1.15 ± 0.37 mm at 1 week to 1.33 ± 0.44 mm at 3 months (p=0.003) and 1.42 ± 0.49 mm at 6 months (p<0.0001). Mean AW increased from 3.92 ± 0.84 mm² at 1 week to 4.38 ± 0.74 mm² at 3 months (p=0.0008) and 4.31 ± 0.87 mm² (p=0.005) at 6 months. Mean AB changed from 5.07 ± 1.86 mm² at 1 week to 5.88 ± 2.42 mm² at 3 months (p=0.03) and 5.90 ± 2.24 mm² at 6 months (p=0.02). There was no significant change in mean hC or mean AC at 3 or 6 months compared to values at 1 week.
Changes in bleb morphology over time can be quantified using ASOCT. In successful blebs, there is an increase in bleb height, bleb cross sectional area and bleb wall cross sectional area over time, without a change in bleb cavity height or cross sectional area.
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