OCTA detects early diabetic retinopathy, but not yet screening-ready

Optical coherence tomography angiography (OCTA) can detect retinal microvascular damage in diabetic eyes well before retinopathy becomes clinically visible, according to a new systematic review of 21 studies. Reduced vessel density stood out as the most reliable early warning sign across the literature, but the authors stopped short of endorsing the technology for everyday use, pointing to inconsistent measurements and an absence of standardised imaging protocols as barriers to routine screening.¹

The review, published in the European Journal of Ophthalmology by Loukia A. Politi and colleagues at Aristotle University of Thessaloniki, synthesises evidence on whether OCTA-derived parameters can flag preclinical disease in patients with diabetes who have no or early-stage diabetic retinopathy (DR).¹ DR remains largely asymptomatic until vision-threatening complications set in, and any tool that reliably identifies microvascular injury earlier could reshape how at-risk patients are monitored.

Study design and findings

Following PRISMA methodology, the investigators searched PubMed, PubMed Central, and the Cochrane database through December 2025 and included 21 studies comprising 3,348 eyes—1,014 healthy controls and 2,115 diabetic eyes with no or early retinopathy. Study quality was appraised with the Newcastle-Ottawa Scale. A meta-analysis was deemed unfeasible because of substantial heterogeneity across imaging devices, scan protocols, and analysis methods.¹

Vessel density (VD) was the most consistently reported signal, with reduced density in early DR observed in 13 of 15 studies and a general trend towards progressive reduction as disease severity increased. Findings for the foveal avascular zone (FAZ) were mixed: enlargement was reported in 9 of 17 studies, with inconsistent correlation to progression. Microaneurysms were more frequently identified in diabetic eyes in 3 of 5 studies, and increased vessel tortuosity in 2 of 5. Among the 3 studies reporting diagnostic accuracy, sensitivities ranged from 66.7% to 93.6% and specificities from 70.9% to 91.7%.¹

Clinical context

Diabetic retinopathy is a leading cause of vision loss among working-age adults worldwide. An estimated 103 million people had DR in 2020, a figure anticipated to reach roughly 160 million by 2045 as diabetes prevalence climbs.² Current standard-of-care screening, as reflected in the American Academy of Ophthalmology's Diabetic Retinopathy Preferred Practice Pattern, relies on periodic dilated fundus examination and colour fundus photography to grade retinopathy once clinically visible lesions—microaneurysms, haemorrhages, and neovascularisation—are present.³ That paradigm, by design, detects disease that has already reached the retinal surface, leaving a window of subclinical microvascular change unaddressed.

How OCTA works

OCTA is a non-invasive imaging modality that uses motion contrast from repeated scans to generate high-resolution, depth-resolved maps of retinal and choroidal blood flow, without the dye injection required for conventional fluorescein angiography. Because it quantifies perfusion at the level of the superficial and deep capillary plexuses, it can theoretically capture capillary dropout, FAZ remodelling, and flow deficits before they become ophthalmoscopically visible. Prior systematic reviews and meta-analyses have likewise reported reduced parafoveal vessel density and FAZ enlargement in patients with diabetes who lack clinical retinopathy, supporting biological plausibility for the current findings.^4,5

Interpretation

The consistency of the vessel density signal across independent studies is the review's most clinically meaningful takeaway, aligning with a growing body of OCTA literature. The authors concluded that current evidence is insufficient for routine clinical implementation. The variability in FAZ results, the small number of diagnostic-accuracy studies, and wide performance ranges argue against adopting any single parameter as a standalone screening threshold today.¹

Limitations and next steps

The principal limitation is heterogeneity. Differences in OCTA hardware, scan dimensions, segmentation algorithms, and definitions of early disease precluded quantitative pooling and complicated cross-study comparison—an obstacle that efforts to standardise OCTA biomarkers in diabetic retinal disease are attempting to address.⁶ Most included studies were cross-sectional, limiting inferences about whether early OCTA changes predict progression to vision-threatening DR.

The authors call for larger, prospective, standardised studies with harmonised imaging protocols and normative reference ranges before OCTA can be positioned as a screening or risk-stratification tool. As a narrative literature review, the analysis was not prospectively registered.¹

REFERENCES

1. Politi LA, Pitoulias AG, Pitoulias MG, Topouzis F. Diagnostic potential of OCTA for early detection of diabetic retinopathy: a literature review. Eur J Ophthalmol. Published online August 8, 2026. doi:10.1177/11206721261476180. https://journals.sagepub.com/doi/10.1177/11206721261476180

2. Teo ZL, Tham YC, Yu M, et al. Global prevalence of diabetic retinopathy and projection of burden through 2045: systematic review and meta-analysis. Ophthalmology. 2021;128(11):1580-1591. doi:10.1016/j.ophtha.2021.04.027. https://www.aaojournal.org/article/S0161-6420(21)00321-3/fulltext

3. American Academy of Ophthalmology. Diabetic Retinopathy Preferred Practice Pattern. Updated 2024. https://www.aao.org/education/preferred-practice-pattern/diabetic-retinopathy-ppp

4. Optical coherence tomography angiography for detection of microvascular changes in early diabetes: a systematic review and meta-analysis. PubMed record. 2024. https://pubmed.ncbi.nlm.nih.gov/38738481/

5. Early detection of microvascular impairments with optical coherence tomography angiography in diabetic patients without clinical retinopathy: a meta-analysis. PubMed record. 2020. https://pubmed.ncbi.nlm.nih.gov/32976846/

6. Standardization of optical coherence tomography angiography imaging biomarkers in diabetic retinal disease. Ophthalmic Res. https://karger.com/ore/article/64/6/871/829022/Standardization-of-Optical-Coherence-Tomography