Anterior-segment OCT (AS-OCT) and intraoperative OCT (iOCT) for trans-conjunctival needle revision (TCNR) of trabeculectomy bleb

Trabeculectomy is one of the most commonly performed glaucoma procedures to control intraocular pressure. A major complication of trabeculectomy surgery is failure due to the formation of excessive fibrotic tissue. Fibrosis of the conjunctiva to the underlying scleral or fibrosis of the scleral flap itself can limit flow. Transconjunctival needle revision (TCNR) is an effective way to resurrect a failing trabeculectomy, however, it is difficult to predict the likelihood of success based on the clinical examination. The anatomy of a trabeculectomy bleb can be complex with multiple loculations of fluid, with or without the presence of a Tenon’s cyst. Accordingly, it can be difficult to determine the location and extent of the fibrotic barrier to the egress of aqueous humor since it is difficult to visualize the fibrotic tissue with slit lamp biomicroscopy or intraoperatively with the surgical microscope. Intraoperative optical coherence tomography (iOCT) has become available but its use in glaucoma surgery remains limited. Pre-operative Anterior Segment OCT (AS-OCT) and iOCT of the filtering bleb may provide information on the morphology of the bleb and extent and location of fibrotic tissue. Furthermore, iOCT may impact surgical decision-making and provide information on whether adequate lysis of fibrotic adhesions has been performed at the conclusion of the case. The aim of this prospective study is to assess the feasibility and utility of pre-operative AS-OCT and iOCT-assisted TCNR of trabeculectomy bleb. Furthermore, we will assess whether pre-operative AS-OCT can be used to predict TCNR success. We aim to recruit 20 patients with glaucoma with trabeulectomy-failure clinically attributed to fibrosis (as defined by elevated intraocular pressure and bleb morphology at the time of slit lamp biomicroscopy) who has been advised and consented to undergo TCNR by a glaucoma specialist at Northwestern Medicine. These patients will undergo detailed slit lamp exam and pre-operative AS-OCT (Spectralis, Heidelberg) of the filtering bleb as part of a routine clinic visit. During the TCNR procedure, iOCT (Zeiss Artevo 800, Carl Zeiss Meditec AG) integrated with operating microscope will be used to image the bleb during surgery to assess for lysis of adhesions and formation of hyporeflective cavity inside the bleb. Patients will be followed post-operatively for a minimum of 3 months for monitoring of intraocular pressure and presence of complications.