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Andrew Scott, Dawn A Sim, Pearse Andrew Keane, Ashkan Khalili, Marcus Fruttiger, Jonathan C Clarke, Peng Tee Khaw, Catherine A Egan, Adnan Tufail; A novel system for vascularity grading of drainage blebs after trabeculectomy surgery using Optical Coherence Tomography Angiography. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2723. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Vascularity of blebs reflects inflammation and this is one of the most important predictors of the likelihood of glaucoma filtration surgery failure and poor intraocular pressure control. The Moorfields Bleb grading system (MBGS) is a highly reproducible system which requires evaluators to grade blebs including vascularity based on comparisons to standard photos. This system however fails to capture vessels deeper to the conjunctiva. It is now possible to perform rapid, non-invasive angiography using optical coherence tomography (OCT).
We developed a method to acquire OCT angiography images of trabeculectomy blebs and surrounding conjunctiva and sclera using the Avanti Angiovue spectral domain OCT (Optovue, Inc. Fremont, CA, USA). The flow imaging is based on split-spectrum amplitude decorrelation angiography (SSADA) and was made possible in the conjunctiva by the cornea-anterior module lens (CAM L) attachment. We acquired concurrent OCT angiographic and colour photographic images on 5 trabeculectomy blebs that were previously graded on the vascularity scale of the MBGS as avascular (grade 1), normal (grade 2), mild vessel inflammation (grade 3) , moderate vessel inflammation (grade 4) and severe vessel inflammation (grade 5) and scored for 3 zones: central bleb, bleb edge and non-bleb conjunctiva.
OCT angiography of blebs and surrounding conjunctiva using angioretina module with CAM L attachment was possible and provided detailed imaging of the deeper vessels within tenon capsule and the deeper vascular plexus not captured by colour photograph.
OCT angiography has for the first time provided an insight into the perfusion of all layers of the bleb and surrounding conjunctiva. This has potential for a novel system of vascularity grading and may be a powerful research tool to better understand, predict and modify outcomes of glaucoma surgery.
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