Digital Analysis of Intraoperative Fluorescein Channelography in Human Eyes During Ab-Interno Canaloplasty

Ab-interno canaloplasty (AbiC) is a minimally invasive glaucoma surgery designed to enhance physiological aqueous humor outflow by circumferential dilation of Schlemm's canal. While fluorescein channelography has been used intraoperatively during ab-externo canaloplasty to visualize outflow pathways, its quantitative application during AbiC has not yet been evaluated. This study introduces a standardized workflow for quantitative analysis of intraoperative fluorescein channelography during AbiC, with the aim of assessing aqueous humor outflow patterns and their potential predictive value for surgical outcomes. For this purpose, AbiC was performed with fluorescein-dyed viscoelastic and early and late phase channelography images were acquired intraoperatively. A step-by-step image analysis workflow using the open-source image analysis software was developed to quantify subconjunctival fluorescein staining. Three complementary approaches were applied: Measurement of circumferential staining intensity using concentric rings around the cornea, Quadrant-based analysis of segmental staining, and qualitative assessment of focal staining patterns corresponding to possible sites of trabecular meshwork alteration. Exemplary cases suggested that extensive and homogeneous fluorescein staining across quadrants was associated with sustained intraocular pressure reduction and medication independence, whereas limited and heterogenous staining were observed in eyes with less favourable outcomes. This workflow therefore enables a reproducible, quantitative assessment of aqueous humor outflow during AbiC, without requiring expertise in image analysis, and can be used to predict the success of minimally invasive glaucoma surgery.