Optical coherence tomography angiography in glaucoma

Methodological quality of the review:  Low confidence

Authors: Bojikian KD, Chen PP, Wen JC

Region: Not reported

Sector:  Glaucoma

Sub-sector: Optical coherence tomography angiography; diagnosis

Equity focus: None specified

Review type: Other review

Quantitative synthesis method: Narrative synthesis

Qualitative synthesis method: Not applicable

Background:

Glaucoma is the leading cause of irreversible blindness worldwide. Several techniques exist for the diagnosis and follow-up of patients. Optical coherence tomography (OCT) angiography (OCTA) is a recently developed technique that provides a quantitative assessment of the microcirculation of the retina and choroid in a fast, noninvasive way. Despite it being a novel technique, several publications have already been done in the glaucoma field. However, a summary of findings is lacking.

Objectives:

To assess the role of OCTA in glaucoma diagnosis and follow-up.

Main findings:

In total, 80 references were included in the review. The authors report that OCTA

1) has a high repeatability and reproducibility,

2) has good discriminatory power to differentiate normal eyes from glaucoma eyes,

3) is more strongly correlated with visual function than conventional OCT,

4) has good discriminatory power to differentiate early-glaucoma eyes from normal eyes (that is, at least equal to that of OCT),

5) reaches a floor effect at a more advanced disease stage than OCT, and

6) is able to detect progression in glaucoma eyes.

The authors note that OCTA has the advantage of being a reliable, objective technique with a high repeatability and reproducibility. OCTA is also faster than visual field testing and relies much less on patient cooperation.

When compared to standard OCT, OCTA

• had a comparable discriminatory power to differentiate between normal and glaucoma eyes,
• combined with OCT resulted in the best AUC to differentiate between normal and glaucoma eyes,
• parameters were more strongly correlated with visual function than OCT parameters, and
• offers a clear benefit in GS/PPG and advanced glaucoma cases.

Given these promising results, the authors believe that OCTA may in the future become a part of everyday glaucoma management, alongside OCT and visual field testing.

Methodology: 

The authors included studies evaluating the role of OCTA in glaucoma patients. Only original research published in English was included. No publication year restrictions were applied by the authors. Animal studies, in vitro studies, and reviews were excluded.

The authors conducted a search on Embase, Web of Science and Medline from inception. Abstracts from the 2017 abstract book from the Annual Meeting of the Association for Research in Vision and Ophthalmology (ARVO) were included. In addition, the authors also screened references of studies.

The authors used four types of OCT algorithms in the selected studies:

• the split-spectrum amplitude decorrelation angiography (SSADA) algorithm described in detail by Jia et al.,
• the OCT-based microangiography (OMAG) described in detail by Zhang and Wang,
• the OCTA ratio analysis (OCTARA) described by Stanga et al., and
• the speckle variance OCTA described in detail by Xu et al.

Applicability/external validity:

The authors do not discuss the applicability or external validity of findings.

Geographic focus

Not reported

Summary of quality assessment:

Overall, there is low confidence in the conclusions about the effects of this study. Important limitations of this study include the lack of detail on the methods used to extract data of included studies; the lack of clarity on the risk of bias of included studies and limitations of the search strategy used by the authors.