Navigating the Angles: A Retrospective Analysis of One-year Outcomes of Gonioscopy-assisted Transluminal Trabeculotomy in Primary Open-angle Glaucoma

Summary

Gonioscopy-assisted transluminal trabeculotomy significantly reduces intraocular pressure and medication in patients with primary open-angle glaucoma. Postoperative angle changes include forward iris insertion, narrowing angle width, pigment reduction and accumulation, and frequent PAS formation, predominantly in the nasal quadrant. These effects remain stable through the 12-month follow-up.

Abstract

This study aimed to evaluate postoperative angle changes following gonioscopy-assisted transluminal trabeculotomy (GATT) in patients with primary open-angle glaucoma (POAG) over 1 year of follow-up. We conducted a retrospective analysis of 60 eyes from 41 POAG patients who underwent GATT, assessing intraocular pressure (IOP), number of ocular hypotensive medications, and gonioscopic findings preoperatively and at 3, 6, and 12 months postoperatively using the Spaeth classification. Postoperative IOP and medication use were significantly reduced throughout follow-up. Gonioscopic examination revealed forward movement of the iris root insertion in all quadrants, most notably inferiorly, with angle width narrowing up to 10°, primarily in the nasal quadrant. Overall pigment angle decreased initially, then gradually increased, with the nasal quadrant showing the highest pigment levels; the pigment pattern changed from diffuse preoperatively to stacked postoperatively. Peripheral anterior synechia (PAS) developed in 39 eyes (65%) and stabilized by 3 months, with the nasal quadrant most affected and showing a gradually increasing extent of involvement. Regarding the trabeculotomy cleft, 28 eyes (46.7%) maintained a widely patent opening, 29 (48.3%) showed a narrow opening, and 3 (5%) were completely closed. Angle rebleeding sites varied among patients, occurring most frequently in the nasal quadrant. In conclusion, GATT significantly reduced IOP and medication use over 12 months, with characteristic angle changes including forward iris insertion, narrowing angle width, altered pigment distribution with accumulation, predominant PAS formation in the nasal quadrant, and variable rebleeding sites.

Introduction

Primary open-angle glaucoma (POAG) is characterized by progressive optic neuropathy driven primarily by elevated intraocular pressure (IOP) due to impaired aqueous humor outflow through the trabecular meshwork (TM)-Schlemm's canal pathway^1,2. While traditional filtering surgeries create alternative drainage pathways, they are associated with significant complications and bleb-related morbidity. Gonioscopy-assisted transluminal trabeculotomy (GATT), an ab interno circumferential trabeculotomy, has emerged as a minimally invasive alternative that targets the pathological resistance directly by incising the T....

Protocol

Study design
All research procedures involving human participants were conducted in accordance with the Declaration of Helsinki and approved by the Institutional Review Board (IRB) of Chengdu First People's Hospital (Approval ID: CDFPR-2024-GATT-018)⁹. Written informed consent was obtained from all participants prior to enrollment, detailing the surgical procedure, potential risks, and longitudinal follow-up requirements. The study employs a retrospective cohort design with standardized data collection protocols implemented in November 2018, enabling analysis of consecutive patients through November 2023.

Results

This retrospective study analyzed gonioscopic data from 60 eyes of 41 patients with POAG, comprising 36 male eyes (60%) and 24 female eyes (40%), with a mean age of 51.8 ± 15.4 years. Following GATT, both IOP and the number of ocular hypotensive medications were significantly reduced compared to baseline (both P < 0.001; Table 1). Significant morphological alterations in the angle structure were observed postoperatively when comparing preoperative and 1-year follow-up gonioscopic findings (

Discussion

This study demonstrates that GATT effectively lowers IOP and reduces medication dependence in POAG patients by restoring physiological aqueous humor drainage through trabecular meshwork incision. Our serial gonioscopic observations revealed characteristic postoperative anatomical changes: anterior displacement of the iris root insertion, overall angle narrowing, fluctuating angle pigmentation, and progressive peripheral anterior synechiae (PAS) formation predominantly in the nasal quadrant. It is important to note that w.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Anterior segment OCT system (RTVue 100-2)	Optovue	Retinal nerve fiber layer analysis
Balanced salt solution / irrigation solution	Alcon (BSS)	Anterior chamber irrigation
Carbamazepine retractor / iris retractor	ASICO	Used during surgical exposure
Diclofenac sodium ophthalmic solution	Novartis	Postoperative NSAID
Eyelid speculum	Rhein Medical	Maintains eyelid opening during surgery
Four-mirror gonioscopy lens	Volk	Angle visualization
Humphrey Field Analyzer HFA-750i	Carl Zeiss Meditec	Visual field testing
Illuminated microcatheter for trabeculotomy	Ellex	360° canalization of Schlemm's canal
Levofloxacin ophthalmic solution	Santen Pharmaceutical	Postoperative antibiotic
Microforceps	DORC	Manipulation of catheter and tissue
Microknife 25G	Alcon	Goniotomy incision
Pilocarpine ophthalmic drops	Novartis	Postoperative miotic
Prednisolone acetate ophthalmic suspension (Pred Forte)	Allergan	Topical corticosteroid
Proparacaine hydrochloride 0.5% ophthalmic solution	Bausch & Lomb	Topical anesthetic
SPSS Statistics 25.0	IBM	Statistical analysis software
Slit-lamp biomicroscope	Zeiss	Anterior segment examination
Snellen visual acuity chart	Precision Vision	Visual acuity testing
Viscoelastic ophthalmic surgical device	Bausch & Lomb	Maintains anterior chamber depth during surgery