OCT-Angiography detects longitudinal microvascular changes in glaucoma: a systematic review

Author: Miguel A, Silva A, Barbosa-Breda J, Azevedo L, Abdulrahman A, Hereth E, Abegão Pinto L, Lachkar Y, Stalmans I.

Geographical coverage: Not reported

Sector: Glaucoma

Sub-sector: Screening, diagnosis

Equity focus: Not reported

Study population: Patients with glaucoma

Review type: Effectiveness review

Quantitative synthesis method: Narrative synthesis (a meta-analysis was planned but could not be conducted due to marked heterogeneity in methods of the included studies)

Qualitative synthesis method: Not applicable

Background

Optical coherence tomography angiography (OCTA) is a non-invasive imaging technology that produces high-resolution images of retinal and optic nerve vascular structures without the need for contrast agents. OCTA offers advantages over traditional optical coherence tomography (OCT), particularly in challenging cases such as myopic eyes. It can detect reductions in vessel density (VD), even in advanced stages of disease where OCT may fail to show measurable changes. Although previous studies and meta-analyses have shown OCTA’s value in diagnosing glaucoma, no systematic review has been conducted on longitudinal VD changes in glaucoma patients.

Objectives

To conduct a systematic review of studies investigating longitudinal changes in peripapillary and macular vessel density (VD) in patients with glaucoma.

Main findings

OCTA appears to be a promising tool for monitoring microvascular changes in glaucoma.

From 4,516 records screened, 10 studies were included in the review. Follow-up durations ranged from 3 months to 2.6 years. Outcomes varied significantly across studies. The annual rate of vessel density (VD) change in glaucoma patients ranged from 0.036 to 1.08 units and 1.3% to 3.2%, with glaucoma patients showing significantly greater changes compared to healthy controls.

Five studies examined VD changes after glaucoma surgery. Findings were inconsistent, with some reporting a temporary decrease in VD and others showing an increase three months postoperatively.

Due to methodological heterogeneity—differences in devices, regions of interest, measurement slabs, and time points—a meta-analysis could not be performed. Findings were synthesised narratively.

Methodology

Searches were conducted in Medline, SCOPUS, ISI Web of Science, and Google Scholar to identify longitudinal studies involving patients with primary open-angle glaucoma (POAG) and reporting OCTA-based measurements of glaucomatous changes. Studies published from inception up to 20 September 2019 with a minimum follow-up of three months were eligible for inclusion.

Reference lists of included studies, relevant reviews, grey literature, and unpublished data were also screened. Authors were contacted to obtain missing information. No language or geographical restrictions were applied.

Two reviewers independently screened articles for inclusion and assessed study quality using the Cochrane Risk of Bias Tool and the STROBE checklist. Any disagreements were resolved through discussion or by consulting a third reviewer. Data were synthesised by two reviewers. Planned subgroup analyses included glaucoma subtype, device used, minimum scan quality, and surgical versus non-surgical studies.

Applicability / External validity

The review noted that variability in study design, devices, and VD measurement methods limits the ability to draw strong clinical conclusions. The authors recommended the adoption of standardised protocols in future research to improve reliability and clinical applicability of OCTA in glaucoma monitoring.

Geographic focus

The geographic origin of the included studies was not reported.

Summary of quality assessment

There is high confidence in the conclusions drawn by this review, given the systematic methodology and use of established quality appraisal tools.