Postural changes in retinal vascular parameters and risk of diabetic retinopathy progression in type 2 diabetes mellitus: a pilot study.

Background: To investigate whether postural changes in retinal vascular parameters, measured using smartphone-based imaging, differ between healthy individuals and patients with diabetes mellitus (DM), and whether these changes independently predict diabetic retinopathy (DR) progression over a 5-year period.

Methods: Retinal images were captured using a smartphone with a clip-on adapter lens in sitting and supine positions. Vascular parameters (caliber, fractal dimension, tortuosity, branching) were quantified using the Singapore I Vessel Assessment software. Cross-sectional analyses compared postural-induced vascular responses between 38 healthy controls and 49 DM participants. DM participants were followed for 5 years, with DR progression defined as ≥ 2-step increase in severity on the Early Treatment Diabetic Retinopathy Study scale. Cox proportional hazards models evaluated associations between baseline postural changes and DR progression.

Results: Healthy controls exhibited significant arteriolar and venular constriction upon moving from sitting to supine (P < 0.05). In contrast, participants with DM showed diminished or paradoxical responses that did not reach statistical significance. Significant linear trends were observed for arteriolar caliber, fractal dimension, and simple tortuosity across healthy controls, DM with and without DR (all P-trend < 0.05). Greater arteriolar tortuosity was associated with a 2.41-fold higher risk of DR progression (HR = 2.41, 95% CI: 1.37-4.23; P = 0.002), while wider venular branching angles correlated with a 45% lower risk (HR = 0.55, 95% CI: 0.35-0.87; P = 0.011). Adding these parameters improved predictive discrimination beyond established factors (arteriolar tortuosity: C-statistic 0.630-0.740; venular branching angle: 0.630-0.683; P < 0.05).

Conclusions: Smartphone-based imaging of retinal vascular responses to postural changes provides additional prognostic value for DR progression, potentially enhancing early risk stratification and proactive management.