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

Summary

This study presents a standardized open-source workflow for quantifying intraoperative fluorescein channelography during ab-interno canaloplasty, which can be used to assess aqueous humor outflow patterns and potentially predict the postoperative outcome with regard to intraocular pressure.

Abstract

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.

Introduction

Glaucoma is a multifactorial disease with progressive optic neuropathy and one of the most common causes of blindness worldwide^1,2. Various factors have been identified that contribute to pathogenesis of glaucoma - including structural vulnerability of the lamina cribrosa, impaired ocular perfusion, genetics and autoimmune processes - but the only modifiable risk factor remains elevated intraocular pressure (IOP)^3,4,5,6,7,

Protocol

Ethical Statement:

This study was conducted in accordance with the Declaration of Helsinki. It was considered non-interventional as it was a retrospective review of patient data collected as part of regular medical practice. No prospective therapeutic approaches were pursued, and all treatments were given routinely as part of standard care. The Bonn Ethics Committee reviewed the study protocol and waived informed consent given the non-interventional design (no. 2026-220). Patient data were de-identified prior to analysis.

1. AbiC and Intraoperative Channelography

Results

Patients over the age of 18 with a diagnosis of glaucoma who had undergone AbiC either standalone or in combination with cataract surgery were included. In addition, channelography images had to be available at least in the early or late phase. A previous selective laser trabeculoplasty was not an exclusion criterion, in contrast to other glaucoma surgical procedures. In addition, no patients with advanced glaucoma damage were included in the study.

So far, we have been able to include a total.......

Discussion

This workflow provides a step-by-step guide to use open-source image analysis software to quantify the amount of aqueous humor outflow after AbiC. The features of open-source image analysis software provide easy-to-use templates that do not require any coding knowledge and can be applied by physicians without technical support. This approach will help to evaluate aqueous humor outflow after AbiC to assess its potential predictive value for surgical outcomes. Rather than representing a direct functional measurement, the w.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Balanced Salt Solution	Bausch & Lomb	Ref.: BL705004
Bi-manual irrigation/aspiration probes	Zeiss	Ref.: 303060-0165-000
Cefuroxim	Laboratoires Théa	PZN: 09755705	Pre-mixed by the pharmacy
Dexamethasone	Dr. Winzer	PZN: 02192162
FIJI (ImageJ)	n/a	n/a	Open-source image analysis software
Fluorescein dye	Alcon	PZN: 01467007
Healon Pro Viscoelastic	Johnson & Johnson	Ref.: 10-3100-12
Hydroxymethylcellulose	Johnson & Johnson	Ref.: 10310012
Iodine solution	Mundipharma	PZN: 03930490
iPrism S gonioprism lens	Glaukos	Ref.: OTB/LH-2
iTrack Advance Canaloplasty System	Nova Eye Medical	Ref.: Track-ADS	Microcatheter-based canaloplasty system
Lumera 700 Surgical Microscope + Calysto	Zeiss	Ref.: 6726521526	Ophthalmic surgical microscope
Proxymetacaine hydrochloride	PUREN Pharma GmbH & Co. KG	PZN: 11055866
Sterile cannula	Braun	Ref.: 4657683