In Vivo Imaging and Impression Cytology Analysis of Conjunctival Changes as Potential Indicators for Ab-interno Gelatin Microstent Implantation Surgery Outcomes

Trabeculectomy and XEN45 gel stent implantation are glaucoma surgeries that creates an aqueous humor (AH) shunt towards the subconjunctival space (filtration bleb). Once the AH reaches the subconjunctival space, it is removed by different paths such as the trans-bleb wall route. For this reason, the conjunctiva is considered an essential structure that may condition the glaucoma filtering procedures outcomes. As part of the inflammatory response, an unbalanced fibrosis during the postoperative period may lead to a bleb cavity scarring and failure; for this reason, bleb massage and antifibrotic injections (i.e., 5-Fluoruracil) are frequently required as part of the postoperative care of these procedures. There have been described several risk factors, such as intraocular pressure (IOP) lowering medications, previous surgical interventions or ocular surface disease that may predispose to an early failure. These preoperative factors fail to aim to predict the surgical outcomes.

However, ocular biomarkers may overcome this limitation. There are promising studies that have analyzed the role of in vivo confocal microscopy (IVCM), anterior-segment optical coherence tomography (AS-OCT) and conjunctival cytology impression as clinical tools that may improve the filtration bleb assessment at a cellular level.