Chorioretinal microvascular changes in slow flow coronary phenomenon: a multi-center study.

We compared chorioretinal microvascular of Slow Coronary Flow Phenomenon (SCFP) patients using Optical Coherence Tomography Angiography (OCTA) to healthy controls. We recruited 21 patients from September 2023 until January 2024 from two referral centers. We enrolled 21 age-sex-matched controls retrospectively. Patients were referred to obtain OCTA in our outpatient ophthalmology clinic. The OCTA and Enhanced Depth Imaging (EDI) OCT findings were measured. Whole image and perifoveal Vascular Density (VD) of superficial and deep capillary plexuses and Parafoveal VD of superficial layer were diminished in SCFP groups compared to controls (p < 0.05) while both superficial and deep foveal VD and deep parafoveal VD were spared. Sub-Foveal Choroidal Thickness (SFCT) was significantly thinned compared to controls (p < 0.05), while central macular thickness, choroidal vascularity index, and choriocapillaris flow were similar between groups. SFCT was the only independent predictor of SCFP on multivariable regression analysis. Parafoveal superficial VD and SFCT showed the strongest ability to distinguish between SCFP patients and healthy controls (AUC: 0.80, 0.79, respectively). Additionally, whole image and perifoveal VD in both superficial and deep capillary plexus demonstrated at least moderate discriminatory power. We found that decreased retinal microvascular density may serve as a potential biomarker for the diagnosis of SCFP. Additionally, SCFP patients had considerably thinner SFCTs than controls. Parafoveal superficial VD and SFCT showed the highest potential in distinguishing between individuals with SCFP and healthy individuals. SCFP is likely linked to anomalies in the small blood vessels of the retina and choroid. However, further studies are needed to confirm this association and to control for the potential confounding effects of diabetes and hypertension.