Title : Morphological and functional assessment of filtering blebs on anterior segment optical coherence tomography
Glaucoma has been surgically treated by various surgical procedures and one of them is trabeculectomy. Bleb morphology in addition to various characteristics by classification systems is an important clinical parameter that indicates bleb function and predicts bleb-related complications. Successful blebs are elevated and diffuse with a cystic pattern, but failed blebs are either flat, encapsulated or profusely vascularized. Filtering bleb function can be evaluated subjectively by slit-lamp examination, but the connective tissue hinders the observation at depth. Ultrasound biomicroscopy (UBM) and in vivo confocal microscopy are not viable options for bleb evaluation in the early postoperative period, due to the increased risk of bleb infection and its damage. Indiana Bleb Appearance Grading Scale (IBAGS) and Moorfields Bleb Grading System have been introduced for objective clinical evaluation and classification of filtering blebs. Cross-sectional non-invasive imaging modalities like anterior segment optical coherence tomography (AS-OCT) can depict the internal structures of blebs and thus provide complementary information to slit-lamp biomicroscopy about the morphological structure and functionality of filtering blebs. AS-OCT helps to provide a high-resolution, non-contact, cross-sectional objective evaluation of filtering blebs and their internal visualization and may be used to predict the functioning of blebs at a later stage.
AS-OCT could be considered a useful tool for examining the internal structures of the filtering blebs for evaluating their function. Bleb morphology, which is not visible on the slit-lamp, can be imaged on AS-OCT. It can differentiate functional from scarred blebs and planning like needling and bleb revision for encapsulated blebs can be done to make them functional. Blebs with thick walls, more height, and multiple hypo-reflective spaces control IOP effectively. They can be considered successful blebs for long-term months and predict the success of trabeculectomy.