Precise Identification of Filtration Openings on the Scleral Flap by Three-Dimensional Anterior Segment Optical Coherence Tomography

Abstract

To elucidate the potential of three-dimensional anterior segment optical coherence tomography (3D AS-OCT) for identifying filtration openings where aqueous humor flows from the sclera into the subconjunctival space. We used 3D AS-OCT and custom software to identify filtration openings, which were defined by pits and/or troughs in fluid-filled cavities in both horizontal and vertical rasters and corresponding C-scan images of scleral flap margin in the blebs. We measured bleb parameters, and at least three different reviewers surveyed the complete 3D images of the internal structure of the filtration blebs and associated findings. We identified filtration openings in 118 (95%) of 124 eyes. Among these 118 eyes, we found only a single filtration opening in 90 eyes (76%) and two or more filtration openings in the remaining 28 eyes (24%). Filtration openings were located in the middle third of the scleral flap margins in 57 eyes (63%) of the 90 eyes. The pattern of incision and sutures used for closure of the conjunctival flap affected the location of the openings, but additional laser suture lysis did not. In 6 (5%) of the 124 eyes, filtration openings could not be identified because of high reflectivity and/or elevated bleb wall (2 eyes), and no fluid-filled cavities because a sponge-like structure masked the filtration openings just above the scleral flap (4 eyes). 3D AS-OCT allows, in most cases, detailed evaluation of internal morphology of filtration blebs and precise identification of filtration openings on the scleral flap margins after trabeculectomy.