Vessel Evaluation in Patients with Primary Open-Angle Glaucoma, Normal Tension Glaucoma and Healthy Controls

Abstract

Purpose

To compare changes in central retinal arterial equivalent (CRAE), central retinal vein equivalent (CRVE), arteriovenous ratio (AVR), tortuosity and fractal dimension in primary open-angle glaucoma (POAG), normal-tension glaucoma (NTG) and in a control group (CG) on fundus photographs. Further, to provide further evidence of vascular change in glaucoma patients using a novel method of tortuosity.

Patients and Methods

The primary endpoint was the change in CRAE, CRVE, AVR, fractal dimension and tortuosity of the retinal vasculature from baseline, retrospectively analyzed from 2011 to 2017 at the University Eye Hospital Tuebingen. Fundus photos of POAG (N = 49), NTG (N = 38) and CG (N = 18) were computer evaluated and analyzed in the quantities mentioned above.

Results

CRAE in NTG and POAG and CRVE in NTG significantly decreased (P = 0.02, P = 0.01; P = 0.03) whereas CRVE in POAG increased insignificantly (P = 0.72). In NTG, AVR decreased significantly (P = 0.05), but to a lesser extent than in POAG (P < 0.001). In CG, CRAE decreased insignificantly (P = 0.10), CRVE decreased significantly (P = 0.03) and AVR increased insignificantly (P = 0.77). In POAG tortuosity calculated using standard methods as well as our novel method, increased significantly (P = 0.015–0.04), whereas it did not occur in NTG (P = 0.18–0.57) and CG (P = 0.11–0.21). Fractal dimensions in POAG decreased significantly (P = 0.001–0.002), whereas in NTG and CG changes were insignificant (P = 0.33–0.92).

Conclusion

Based on a retrospective analysis of fundus photographs, specific retinal vasculature features of the retinal vasculature display significant alterations associated with NTG and POAG. The assessment of tortuosity using our novel method was consistent with previously established methods for analyzing tortuosity.

Keywords:

• AVR
• CRAE
• CRVE
• tortuosity of vessels
• fractal dimensions

Data Sharing Statement

For code availability of the vessel-segmentation, vessel-classification and optic-disc-detection/segmentation algorithm we refer to the respective original publications [28, 29, 30].

Ethics Approval and Consent to Participate

This study was approved by the ethics commission of Tuebingen in March 2020 (project number: 048/2020BO2) and followed the tenets of the Declaration of Helsinki. In this retrospective study, data was evaluated anonymously after its collection by one person, complying with medial confidentiality.

Acknowledgments

The authors acknowledge support by the High Performance and Cloud Computing Group at the Zentrum für Datenverarbeitung of the University of Tübingen, the state of Baden-Württemberg through bwHPC and the German Research Foundation (DFG) through grant no INST 37/935-1 FUGG. Part of the work concerning the development of algorithms for fundus analysis was supported by a grant of the Charlotte and Tistou Kerstan Foundation.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis, and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

Siegfried Wahl and Iliya V Ivanov are employees of Carl Zeiss Vision International GmbH. Siegfried Wahl reports salary from Carl Zeiss Vision International GmbH, during the conduct of the study. The authors report no other potential conflicts of interest for this work.

Additional information

Funding

The Department of Ophthalmology and Ueffing Marius received partial financial support from the Tistou und Charlotte Kerstan Foundation.