Wider OCTA scan protocols captured greater burden of nonperfusion and microvascular abnormalities, with NPI serving as a robust standalone biomarker across protocols, and combining NPI and IRMA counts improving staging performance when imaging is limited to smaller fields.
Key Findings
Results
NPI and IRMA counts increased with wider scan protocols across all DR severities, with higher neovascularization detection in PDR on wider scans.
Three scan protocols were compared: 6×6 mm, 12×12 mm, and 29×24 mm
110 eyes from 74 treatment-naïve patients with DR were included in this cross-sectional study
NPI, IRMA counts, and NV counts were the primary quantitative biomarkers analyzed
Wider scan fields captured greater burden of nonperfusion and microvascular abnormalities across all DR severity stages
Results
The 29×24 mm scan protocol provided the highest diagnostic performance for NPI in discriminating PDR from NPDR.
AUC for NPI with 29×24 mm scans discriminating PDR from NPDR was 0.86 (95% CI = 0.79–0.93)
This outperformed NPI measured with smaller scan protocols (6×6 mm and 12×12 mm)
ROC analysis was used to evaluate discriminative performance across scan protocols
Results
The 29×24 mm scan protocol provided the highest diagnostic performance for NPI in discriminating advanced-stage DR from early-stage DR.
AUC for NPI with 29×24 mm scans discriminating advanced DR (severe NPDR and PDR) from early DR (mild-moderate NPDR) was 0.92 (95% CI = 0.88–0.97)
Advanced-stage DR was defined as severe NPDR and PDR; early-stage DR was defined as mild-to-moderate NPDR
Performance was superior to that achieved with 6×6 mm and 12×12 mm scan protocols
Results
Combining NPI and IRMA counts on 6×6 mm scans outperformed NPI alone for discriminating advanced from early DR.
Combined NPI and IRMA counts AUC for advanced vs. early DR: 0.87 (95% CI = 0.81–0.94)
NPI alone AUC for advanced vs. early DR on 6×6 mm scans: 0.81 (95% CI = 0.72–0.89)
The combination metric provided a statistically meaningful improvement over the standalone NPI biomarker in the smaller field of view
Results
Combining NPI and IRMA counts on 6×6 mm scans outperformed NPI alone for discriminating PDR from NPDR.
Combined NPI and IRMA counts AUC for PDR vs. NPDR on 6×6 mm scans: 0.82 (95% CI = 0.74–0.91)
NPI alone AUC for PDR vs. NPDR on 6×6 mm scans: 0.73 (95% CI = 0.62–0.83)
This finding supports combining biomarkers as a compensatory strategy when wide-field imaging is unavailable
Results
NPI served as a robust standalone biomarker for DR staging across all three scan protocols.
NPI demonstrated diagnostic utility regardless of whether the 6×6 mm, 12×12 mm, or 29×24 mm protocol was used
Performance improved progressively with wider scan fields, but NPI remained informative even on the smallest protocol
The study concluded that 'NPI serves as a robust standalone biomarker across protocols'
Conclusions
OCTA scan protocol selection influences quantitative assessment of DR biomarkers and may guide imaging strategies for clinical staging.
The study was cross-sectional and included treatment-naïve patients only, limiting generalizability to treated populations
The findings suggest that protocol choice should be considered when interpreting or comparing OCTA-based DR biomarker measurements
The authors conclude that protocol selection 'may guide imaging strategies for clinical staging'
What This Means
This research suggests that the size of the area imaged during eye scans for diabetic retinopathy (a common diabetes complication affecting the retina) significantly affects how well doctors can detect and measure disease severity. The study used a technology called optical coherence tomography angiography (OCTA), which creates detailed maps of blood vessels in the retina without requiring dye injections. By comparing three different scan sizes—a small 6×6 mm area, a medium 12×12 mm area, and a large 29×24 mm area—in 110 eyes of 74 diabetic patients, the researchers found that larger scans detected more signs of disease, such as areas of poor blood flow (nonperfusion) and abnormal blood vessel growth.
The study found that a measure called the nonperfusion index (NPI), which quantifies how much of the retina lacks adequate blood supply, was the most reliable single indicator across all scan sizes for identifying more advanced stages of diabetic retinopathy. However, larger scan areas gave significantly better results: the largest scan achieved an accuracy (AUC) of 0.92 for distinguishing advanced from early disease, compared to 0.81 for the smallest scan. Importantly, when only smaller scans are available, combining NPI with counts of abnormal blood vessel structures (IRMAs) improved diagnostic accuracy, raising performance from 0.81 to 0.87 for distinguishing disease stages.
This research suggests that clinics and hospitals using OCTA to monitor diabetic retinopathy should be aware that the scan size they choose will affect what they detect and how accurately they can stage disease severity. Wider scans are preferable when available, but combining multiple measurements can partially compensate for the limitations of smaller scans. These findings could help standardize how OCTA is used in clinical practice for diabetic eye disease and may influence decisions about which patients need more comprehensive imaging.
Song W, Tan R, Jayakrishnan A, Oo H, Zhuang L, Seah W, et al.. (2026). Impact of Optical Coherence Tomography Angiography Scan Protocols on Quantitative Microvascular Biomarkers in Diabetic Retinopathy.. Translational vision science & technology. https://doi.org/10.1167/tvst.15.10.18