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Edward Yung, Jonathan P Wright, Alan G Fong, Kevin Kaplowitz, Robert A Honkanen; Wound healing after Trabeculectomy in rabbits: Ultrasound Biomicroscopy (UBM) correlation with clinical findings.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5147.
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© ARVO (1962-2015); The Authors (2016-present)
Evaluation of wound healing in rabbits after trabeculectomy has previously been based on serial clinical examinations and IOP monitoring. We hypothesize that anterior segment ultrasound biomicroscopy can be used to demonstrate objective findings of wound healing and bleb failure correlating to clinical findings in an experimental rabbit model.
Four eyes of four male New Zealand white rabbits underwent limbal-based trabeculectomy ab externo by the same surgeon (RH) without the use of antifibrotic agents. Each eye underwent serial evaluation after surgical intervention with the current standard of Moorefield clinical bleb grading. Ultrasound biomicroscopy was carried out using the Vevo 770 Ultrasound Imaging System (ViewSonic, Toronto, CA) with a RMV704 probe to evaluate the criteria of bleb height, size of cystic spaces, the presence of hypoechoic areas, and visibility of scleral tract. Clinical bleb failure was defined as a Moorfield bleb grading height of 1 or maximal area grading of less than 2. Statistical significance was evaluated with the Student’s t-test.
Average follow up time was 40.5 days post-operatively after trabeculectomy. Mean peak Moorfield bleb height grading was 2.75 ± 0.96, and was demonstrated 2 days post-operatively. Average time to clinical bleb failure was between 11 and 14 days by bleb grading. Ultrasound biomicroscopy evaluation demonstrated baseline conjunctival/bleb thickness of 0.3 ± 0.07 mm. Peak bleb height was 2.95 ± 1.97 mm 2 days after trabeculectomy (p=0.054), followed by a rapid decline in bleb height by post-operative day 9 (1.27 ±0.29 mm, p=0.14). Complete loss of cystic bleb spaces was found by post-operative day 14 in all 4 cases. Loss of hypoechoic regions was demonstrated after an average of 10.75 ± 2.36 days post-operatively and occurred in all four eyes by post-operative day 14.
Our results demonstrate that UBM yields objective indicators of bleb failure that correlate well with clinical findings. Thus, this imaging modality can be a valuable adjunct to clinical examination for evaluating bleb survival in experimental rabbit models of glaucoma filtering surgery. Further studies with a larger population size will be needed to determine statistical significance.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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