Ab Externo Canaloplasty Alone or Combined with Phacoemulsification for Advanced Primary Open-Angle Glaucoma

Summary

This protocol evaluates and compares the clinical efficacy, safety, and patient-reported outcomes of ab externo canaloplasty performed alone or in combination with phacoemulsification in eyes with advanced primary open-angle glaucoma, providing a standardized approach for assessing long-term intraocular pressure control, structural preservation, and quality-of-life improvement.

Abstract

Advanced primary open-angle glaucoma (POAG) requires surgical strategies that achieve effective reduction of intraocular pressure (IOP) while preserving optic nerve structure and function. This study aims to compare the long-term clinical performance of ab externo canaloplasty (AC) alone versus AC combined with phacoemulsification (AC + phaco) in patients with advanced POAG. In this retrospective comparative study, 140 patients with advanced POAG were assigned to AC (n = 70) or AC + phaco (n = 70). Over 24 months of follow-up, both procedures significantly reduced IOP and medication use. However, AC + phaco achieved greater mean IOP reduction (45.5% vs. 36.1%; p < 0.001), higher retinal nerve fiber layer thickness (62.55 ± 6.03 µm vs. 60.82 ± 6.51 µm; p = 0.047), larger neuroretinal rim area (0.91 ± 0.12 mm² vs. 0.85 ± 0.12 mm²; p = 0.009), and improved visual field stability. Quality-of-life measures favored AC + phaco, with improved patient-reported visual function and fewer vision-related limitations. These findings demonstrate that both AC and AC + phaco are safe and effective surgical options for advanced POAG. AC + phaco may be preferentially selected in patients with coexisting cataract or in cases requiring enhanced long-term IOP control and structural preservation, without increasing surgical risk.

Introduction

Primary open-angle glaucoma (POAG) is a progressive optic neuropathy and the second leading cause of irreversible blindness worldwide¹. It is characterized by the degeneration of retinal ganglion cells and optic nerve fibers, resulting in progressive visual field loss and eventual visual disability. Due to its insidious onset and largely asymptomatic early course, POAG is often diagnosed only after substantial structural and functional damage has occurred. With increasing global life expectancy, urbanization, and population aging, the burden of POAG continues to rise, particularly in low- and middle-income regions where access to early screenin....

Protocol

All procedures described in this protocol were reviewed and approved by the Institutional Human Research Ethics Committee of the Third People's Hospital of Dalian University of Technology (Approval No. 2025-176-001). The study was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki. Informed consent was obtained from all participants prior to enrollment.

1. Patient recruitment and screening

NOTE: Patients were recruited consecutively and concurrently from the glaucoma outpatient clinic of the Third People's Hospital of Dalian University of Technology between January 2020 and ....

Results

A total of 200 patients were assessed for eligibility. After excluding patients who did not meet the inclusion criteria or declined to participate, 140 patients with advanced POAG were enrolled and allocated into two groups: AC (n = 70) and AC + phaco (n = 70) (Figure 1).

Baseline clinical characteristics were comparable between the AC group and the AC + phaco group (Table 1). No statistically significant differences were observed between groups i.......

Discussion

The efficacy of Schlemm’s canal–based strategies in slowing the progression of POAG is demonstrated by the consistent IOP reduction pattern observed in both groups. However, statistical analysis showed that the AC + phaco group achieved superior pressure-reducing effects at all postoperative time points. These results are supported by Zhang and Wang³⁸ and Seethe et al.³⁹, who reported significantly greater IOP reduction with combined canaloplasty and phacoemulsi.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Equipment
Automated perimeter (HFA 24-2 SITA-Standard)	Carl Zeiss Meditec	ZEISS-HFA3-860	Visual field indices: MD, PSD at 6, 12, 24 months.
Canaloplasty microcatheter	Nova Eye Medical (iTrack)	NOVA-ITRACK-250	360° Schlemm’s canal catheterization for viscodilation.
Fundus camera / Imaging system	ZEISS (VISUCAM)	ZEISS-VISC-524	Optic disc and posterior pole documentation.
Goldmann applanation tonometer	Haag-Streit AG	HS-GAT-870	Standard IOP measurement; three consecutive readings averaged.
Gonioscopy lens (4-mirror)	Volk Optical	VOLK-G4	Pre-/post-operative angle assessment.
Ophthalmic operating microscope	ZEISS (OPMI Lumera series)	ZEISS-LUMERA-T	Microsurgical visualization.
Phacoemulsification system	Alcon (CENTURION)	ALC-CENT-PHACO	Divide-and-conquer technique; used only in PCP+Phaco group.
Slit-lamp biomicroscope	Topcon	TOP-SLD701	Anterior segment examination and postoperative monitoring.
Spectral-domain OCT (RNFL/GCC)	Heidelberg Engineering (SPECTRALIS)	HE-SDOCT-SPC	Peripapillary RNFL thickness and neuroretinal rim area acquisition.
Consumable
Balanced salt solution (BSS)	Alcon	ALC-BSS-500	Irrigation during anterior segment surgery.
Foldable posterior chamber IOL	Alcon (AcrySof IQ)	ALC-SN60WF	IOL power individualized; acrylic lens implantation.
Microsurgical sutures, Nylon 10-0	Ethicon	ETH-NYL-10-0	Watertight scleral flap closure.
Ophthalmic viscosurgical device (OVD), 1.0% Sodium hyaluronate	Johnson & Johnson Vision (Healon)	JJ-HEALON-10	Maintains anterior chamber; viscodilation support.
Viscodilation cannula (27G)	Nova Eye Medical	NOVA-VD-27G	Controlled viscoelastic delivery into Schlemm’s canal.
Drug
Moxifloxacin 0.5% Ophthalmic solution	Alcon (Vigamox)	ALC-VIG-05	Postoperative topical antibiotic.
Prednisolone acetate 1% Ophthalmic suspension	Allergan (Pred Forte)	AGN-PF-1	Postoperative topical steroid taper.
Timolol 0.5% / Brimonidine 0.2% / Dorzolamide 2% / Latanoprost 0.005%	Various (Generic/Branded)	GLC-RESCUE-SET	IOP-lowering agents as needed per protocol.
Software/Instrument
EQ-5D Instrument (License)	EuroQol Research Foundation	EQ-5D-LIC	General health-related quality of life.
GQL-15 Questionnaire (Permission)	Instrument Owner/Publisher	GQL-15-PERM	Glaucoma-specific disability index.
NEI VFQ-25 Questionnaire (License/Permission)	National Eye Institute	NEI-VFQ25-LIC	Vision-related quality of life assessment.
SPSS Statistics v26	IBM	IBM-SPSS-26	Statistical analysis: t-tests, ANOVA, repeated measures, Kaplan–Meier.