The longitudinal relationship between carotid arterial disease and retinopathy complicating type 2 diabetes: The Fremantle diabetes study phase II

To investigate whether i) ultrasonographically-assessed carotid arterial disease (CAD) is associated with diabetic retinopathy (DR) progression and retinal microangiopathy measured by optical coherence tomography angiography (OCTA), and ii) baseline DR prevalence and/or OCTA parameters are associated with CAD progression in type 2 diabetes. Participants in the Fremantle Diabetes Study Phase II ( n = 164, mean age 69.7 years, 55.5% males) in whom carotid ultrasonography/OCTA was performed in 2018–2019 were restudied a mean 3.7 years later. Generalized estimating equations assessed associations between baseline CAD indices and new/worsening DR and OCTA parameter changes, and between baseline DR status/OCTA parameters and changes in CAD metrics. Carotid stenosis (focal wall thickening ≥50% or intima-media thickness (IMT) > 1.5 mm) and carotid bifurcation IMT ≥1 mm at baseline were independently associated with reductions in superficial capillary plexus parafoveal vessel density (regression coefficients (95% CI) 0.73 (0.02 to 1.43) and 0.88 (95% CI: 0.06 to 1.69); P = 0.043 and 0.035, respectively). There were no independent associations between CAD parameters and new/worsening DR. There were no significant associations between baseline DR/OCTA parameters and new/worsening carotid stenosis. CAD may contribute to early DR in type 2 diabetes but we found no evidence of a bidirectional relationship. • Carotid artery disease (CAD) and diabetic retinopathy (DR) may interact in diabetes. • CAD and retinal vessel density were quantified at 0 and 4 years in type 2 diabetes. • CAD metrics were associated with a reduction in retinal vessel density at 4 years. • DR/retinal vessel density were not associated with CAD progression over time. • CAD may contribute to DR with implications for clinical management.