Keratometric Change After XEN, Trabeculectomy and Tube Shunts

Glaucoma, Open-Angle Clinical Trial

— Topo-XEN  

Official title:

Comparison of Keratometric Change After Xen Gel Stent Implantation, Trabeculectomy, and Tube Shunts

Clinical Trial Details — Status: Recruiting

Administrative data

• NCT number: NCT04602923
• Other study ID #: 20.240
• Status: Recruiting
• Phase: N/A
• Start date: November 4, 2020
• Est. completion date: December 2025

Study information

• Verified date: February 2023
• Source: Centre hospitalier de l'Université de Montréal (CHUM)
• Contact: Marie-Catherine Tessier, MSc
• Phone: 1-514-890-8000
• Email: marie-catherine.tessier.chum[@]ssss.gouv.qc.ca
• Is FDA regulated: No
• Study type: Interventional

Clinical Trial Summary

The main goal of this study is to assess the severity of postoperative corneal astigmatism induced by implantation of the XEN Gel Stent compared to that induced by traditional filtering surgery (trabeculectomy and GDDs). Corneal astigmatism can be assessed using corneal topography, a non-invasive tool which provides an accurate estimate of corneal curvature in all meridians. To the best of our knowledge, no study has yet attempted to quantify the amount of astigmatism induced by the XEN Gel Stent.

Description:

Following glaucoma surgery, patients often experience decreased visual acuity (VA) which can partly be explained by induced changes to the optical properties of the cornea. Corneal astigmatism can be assessed using corneal topography, a non-invasive tool which provides an accurate estimate of corneal curvature in all meridians. Obtained keratometric measures (termed K values) can allow clinicians to quantify the amount of astigmatism before and after surgical intervention.

Multiple studies have been previously published to evaluate induced postoperative astigmatism after trabeculectomy. However, only two studies have characterized the impact of GDDs on keratometric values. To the best of our knowledge, no study has yet attempted to quantify the amount of astigmatism induced by the XEN Gel Stent.

Assessing the impact of the XEN implant on corneal astigmatism is important to better characterize the expected course of postoperative visual rehabilitation, the impact of novel glaucoma devices on corneal properties and the predictability of refractive outcomes after XEN implantation. Compared to traditional filtering surgery, the XEN Gel Stent is inserted without opening the conjunctiva and is implanted further from the corneal limbus (5 mm). These factors may allow for a reduced amount of surgically induced corneal astigmatism.

We hypothesize that the XEN Gel Stent implantation induces less corneal astigmatism compared to traditional filtering surgery, such as the trabeculectomy and GDDs (BGI or AGV).

The main goal of this prospective interventional comparative study is to assess the severity of postoperative corneal astigmatism induced by implantation of the XEN Gel Stent compared to that induced by traditional filtering surgery (trabeculectomy and GDDs).

Secondary objectives are evaluation of visual acuity recovery as well as IOP reduction and other parameters between groups.

Glaucoma surgery (XEN Gel Stent, trabeculectomy or GDD implantation) will be performed by the ophthalmologists in charge of the study according to standard procedures. For each patient, the most appropriate type of glaucoma surgery will be recommended by the ophthalmologist regardless of patients' participation in the study, as dictated by the specific nature of their glaucoma and following current standards of care.

Recruitment information / eligibility

• Status: Recruiting
• Enrollment: 90
• Est. completion date: December 2025
• Est. primary completion date: January 2025
• Accepts healthy volunteers: No
• Gender: All
• Age group: 18 Years and older

Eligibility

Inclusion Criteria:

• Eyes with an IOP above target and/or progressing on maximally tolerated medical therapy;

• Patients aged 18 years or older;

• Ability to provide informed consent;

• Ability to be followed for the entire duration of the study.

Exclusion Criteria:

• Patients less than 18 years old;

• Inability to provide informed consent;

• Inability to be followed for the entire duration of the study;

• Patients undergoing surgery combined with cataract extraction;

• Presence of severe dry eye disease;

• Presence of ocular comorbidities other than glaucoma, such as corneal or retinal disease.

Related Conditions & MeSH terms

• Glaucoma
• Glaucoma Eye
• Glaucoma Secondary
• Glaucoma, Angle-Closure
• Glaucoma, Open-Angle

Intervention

Diagnostic Test:
• Corneal topography: OPD-Scan
Corneal topography photography, taken by specular reflection (OPD-Scan) by measuring corneal curvature, thickness and topography.
• Corneal topography: Pentacam
Corneal topography photography, taken by Scheimpflug imaging (Pentacam) by measuring corneal curvature, thickness and topography.

Locations

Country	Name	City	State
Canada	Centre Hospitalier de l'Université de Montréal (CHUM)	Montreal	Quebec

Sponsors (2)

Lead Sponsor	Collaborator
Centre hospitalier de l'Université de Montréal (CHUM)	Allergan

Country where clinical trial is conducted

Canada, 

References & Publications (9)

Banitt M. Evaluation and management of glaucoma after keratoprosthesis. Curr Opin Ophthalmol. 2011 Mar;22(2):133-6. doi: 10.1097/ICU.0b013e328343723d. — View Citation

Chan HHL, Kong YXG. Glaucoma surgery and induced astigmatism: a systematic review. Eye Vis (Lond). 2017 Nov 17;4:27. doi: 10.1186/s40662-017-0090-x. eCollection 2017. — View Citation

Chatzara A, Chronopoulou I, Theodossiadis G, Theodossiadis P, Chatziralli I. XEN Implant for Glaucoma Treatment: A Review of the Literature. Semin Ophthalmol. 2019;34(2):93-97. doi: 10.1080/08820538.2019.1581820. Epub 2019 Feb 21. — View Citation

Koivusalo R, Valimaki J. Effect of glaucoma drainage implant surgery on corneal topography: a prospective study. Acta Ophthalmol. 2020 May;98(3):305-309. doi: 10.1111/aos.14247. Epub 2019 Sep 8. — View Citation

Lavia C, Dallorto L, Maule M, Ceccarelli M, Fea AM. Minimally-invasive glaucoma surgeries (MIGS) for open angle glaucoma: A systematic review and meta-analysis. PLoS One. 2017 Aug 29;12(8):e0183142. doi: 10.1371/journal.pone.0183142. eCollection 2017. — View Citation

Miraftabi A, Lotfi M, Nilforushan N, Abdolalizadeh P, Jafari S. Ocular biometric changes after Ahmed glaucoma valve implantation. Eur J Ophthalmol. 2021 Jan;31(1):120-124. doi: 10.1177/1120672119889528. Epub 2019 Nov 21. — View Citation

Pakravan M, Alvani A, Esfandiari H, Ghahari E, Yaseri M. Post-trabeculectomy ocular biometric changes. Clin Exp Optom. 2017 Mar;100(2):128-132. doi: 10.1111/cxo.12477. Epub 2016 Sep 29. — View Citation

Quigley HA, Broman AT. The number of people with glaucoma worldwide in 2010 and 2020. Br J Ophthalmol. 2006 Mar;90(3):262-7. doi: 10.1136/bjo.2005.081224. — View Citation

Saheb H, Ahmed II. Micro-invasive glaucoma surgery: current perspectives and future directions. Curr Opin Ophthalmol. 2012 Mar;23(2):96-104. doi: 10.1097/ICU.0b013e32834ff1e7. — View Citation

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Keratometric values (OPD-Scan)	Change in simulated keratometric (K) values obtained by OPD-Scan between the indicated timepoints.	Baseline, 2 months, 6 months, 12 months
Primary	Keratometric values (Pentacam)	Change in simulated keratometric (K) values obtained by Pentacam between the indicated timepoints.	Baseline, 2 months, 6 months, 12 months
Secondary	Best-corrected visual acuity change	Evaluation of visual acuity change, measured using the Snellen chart.	Baseline, 2 months, 6 months, 12 months
Secondary	Intraocular pressure change	Evaluation of intraocular pressure control, measured using gold standard Goldmann applanation tonometry.	Baseline, 2 months, 6 months, 12 months
Secondary	Visual field change change	Evaluation of visual field change. Visual field change will be calculated using the mean deviation (MD) values and pattern standard deviation (PSD) values measured using automated Humphrey 24-2 perimetry.	Baseline, 6 months, 12 months
Secondary	Retinal nerve fiber layer thickness change	Evaluation of retinal nerve fiber layer (RNFL) thickness change (µm), using the average RNFL thickness values measured using Spectral Domain Optical Coherence Tomography (SD-OCT). The change in thickness (µm) will be calculated between the time points described.	Baseline, 6 months, 12 months
Secondary	Ganglion cell layer thickness change	Evaluation of ganglion cell layer (GCL+) thickness. This GCL+ thickness is measured using the values for the average ganglion cell layer and inner plexiform layer thickness of the retina (value called "Average GCL + IPL thickness") obtained by Spectral Domain Optical Coherence Tomography (SD-OCT). The change in thickness (µm) will be calculated between the time points described.	Baseline, 6 months, 12 months