Optical coherence tomography features of neovascularisation in proliferative diabetic retinopathy: a systematic review

Authors: Vaz-Pereira S, Morais-Sarmento T, Esteves Marques R.

Geographical coverage: The USA, Canada, Japan, Saudi Arabia, Venezuela, the UK, Brazil, France, Egypt, Iran, China, Germany, Korea, Switzerland, Singapore, Portugal, Italy and Poland

Sector: Biomedical

Sub-sector: Diagnosis

Equity focus: Not reported

Study population: Patients with proliferative diabetic retinopathy

Review type: Other review

Quantitative synthesis method: Not applicable

Qualitative synthesis method: Narrative synthesis method

Background: Complications of diabetic retinopathy (DR), diabetic macular edema (DME) or proliferative diabetic retinopathy (PDR), are leading causes of blindness. Optical coherence tomography (OCT), a non-invasive imaging technique, is commonly used for DME but comparatively less utilised for evaluating neovascularisation in PDR. Advances in OCT imaging and the advent of OCT angiography (OCTA) have demonstrated considerable promise in the context of PDR.

Objectives: To describe the tomographic features of PDR, namely of retinal (NVE) or disc (NVD) neovascularisation, intraretinal microvascular abnormalities (IRMA), retinal nonperfusion areas (NPA), status of the posterior vitreous, vitreoschisis and vitreous and subhyaloid/sub‑ILM hemorrhages.

Main findings: Of 1,530 studies identified through databases and hand-searches, 60 were included in this qualitative systematic review. The included studies were conducted in various countries around the globe and were of moderate-to-good methodological quality.

OCT proved effective in identifying NVD and NVE, aiding in characterising disease activity and assessing the response to laser and/or anti-vascular endothelial growth factor (VEGF) therapies. The absence of posterior vitreous detachment, with the posterior hyaloid serving as a scaffold, was found to be a determining factor for neovascular growth. OCTA enabled a more detailed characterisation of neovascular complexes, associated NPAs and disease activity, allowing for the quantification of flow index and neovessel area. However, changes in OCTA blood flow signal after local therapies did not always align with structural regression. Widefield and ultra-widefield OCTA demonstrated high sensitivity in detecting PDR, contributing value to disease staging and monitoring. In comparison to fluorescein angiography, OCTA exhibited greater sensitivity in identifying microvascular changes indicative of disease progression.

More research is needed to advance and improve imaging modalities to attain greater benefits in clinical settings.

Methodology: The search was conducted in PubMed and EMBASE to find articles evaluating OCT and/or OCTA findings in patients with PDR. Features of neovascular complexes (NVCs), intraretinal microvascular abnormalities (IRMAs), retinal non-perfusion areas (NPAs), status of the posterior vitreous and subhyaloid/sub-internal limiting membrane (ILM) haemorrhages were focused. The articles published in English, French, Spanish or Portuguese, and published until 19 December 2019, were included. The risk of bias of the included studies was assessed using the Newcastle-Ottawa Scale for observational studies.

Two reviewers conducted the title and abstract, and full-text screening independently. The authors checked reference lists of the included studies to identify additional relevant articles. Data extraction and quality assessment of the included studies were also conducted by two reviewers independently. The authors synthesised the findings narratively.

Applicability/external validity: The authors of the review are confident that they have encompassed the entirety of the literature on the tomographic findings of proliferative diabetic retinopathy (PDR). However, they acknowledge that the representativeness of the cases reviewed may pose challenges to the general applicability of the results.

Geographic focus: The included studies were conducted in various countries around the globe, including the USA, Canada, Japan, Saudi Arabia, Venezuela, the UK, Brazil, France, Egypt, Iran, China, Germany, Korea, Switzerland, Singapore, Portugal, Italy and Poland. The authors did not discuss the applicability of findings to low and middle income settings.

Summary of quality assessment: Overall, there is low confidence in the conclusions about the effects of this study. PubMed and EMBASE were searched to identify relevant articles published in English, French, Spanish or Portuguese. The screening and data extraction were conducted independently by two reviewers. The risk of bias was assessed, and the review did discuss important differences in the results of the included studies. Limitations were acknowledged. However, no source of grey literature was searched. The authors did not report contacting authors/experts.