Optical coherence tomography angiography and microvascular changes in diabetic retinopathy: a systematic review

Authors: Johannesen SK, Viken JN, Vergmann AS, Grauslund J.

Geographical coverage: Not reported

Sector: Biomedical

Sub-sector: Diagnosis

Equity focus: Not reported

Study population: Patients with diabetes mellitus

Review type: Other review

Quantitative synthesis method: Not applicable

Qualitative synthesis method: Narrative synthesis

Background: Optical coherence tomography angiography (OCTA) is a rapid and non-invasive examination of the retinal blood flow that uses motion of erythrocytes to detect the flow in the retinal capillaries. It also has the ability to separate the superficial retinal layer (SRL) and deep retinal layer (DRL), as well as detect microvascular details and capillary changes.

Objectives: To use optical coherence tomography angiography (OCTA) to evaluate foveal microvascular changes in diabetes by comparing the area of foveal avascular zone (FAZ) in healthy controls and patients with diabetes with no diabetic retinopathy (NDR), as well as different stages of diabetic retinopathy (DR).

Main findings: The search identified 358 articles through database searches, of which only 12 were included in this review. Of the 12 included studies, nine were cross-sectional and three were retrospective. Several of the studies provided information for more than one diabetic group. In general, there was a trend towards a larger area of FAZ in patients with diabetes. As compared to healthy controls, this was reported in patients with no diabetic retinopathy (five of eight studies), non-proliferative diabetic retinopathy (seven of eight studies) and proliferative diabetic retinopathy (six of six studies). Overall, this review found a trend of increased foveal capillary drop-out in patients with diabetes as compared to healthy controls, which was particularly evident for patients with advanced levels of DR. The review authors noted the need for longitudinal studies to examine whether OCTA findings could predict long-term structural and functional outcomes.

Methodology: Searches were done in PubMed, EMBASE and the Cochrane Library on 10 September 2017. English language and human subject limits were applied. Studies were included if they compared patients with diabetes mellitus (DM) with patients without DM and with healthy eyes, specified stage of DR, used OCTA as a method for investigation, and reported measurements of area of FAZ in each study group.

The search and screening of the articles were performed by two independent reviewers. The findings were synthesised narratively.

Applicability/external validity:

The authors did not discuss the applicability or external validity of the results.

Geographic focus:

The review authors did not report the geographical distribution of the included studies.

Summary of quality assessment:

The study’s conclusions are met with low confidence due to important limitations identified. The authors conducted searches within PubMed, EMBASE and the Cochrane Library for pertinent articles. However, they did not indicate whether they explored grey literature sources. The review also lacks information on whether reference lists of included articles were examined or if there was any engagement with authors or experts. Restrictions were placed on the inclusion of articles based on the English language. Details regarding the assessment of the risk of bias in the studies and whether data extraction was independently performed by two reviewers are not provided. Additionally, the review does not address the issue of heterogeneity among the studies.