Localization of Microvascular Changes in Systemic Disease Without Retinopathy Using Optical Coherence Tomography Angiography (OCTA)

<b>Background</b>: This study aimed to evaluate the location of retinal fractal dimension (FD) abnormalities in individuals with diabetes mellitus (DM) and hypertension (HTN) without retinopathy. <b>Methods:</b> The annular zone of 6 mm × 6 mm OCTA images centered on the fovea was partitioned into thin annuli and analyzed using fractal analysis to measure FDs. <b>Results:</b> The cohort (<i>n</i> = 114) had an average age of 55.7 years, with 87% self-identifying as male; 29% (<i>n</i> = 33) had HTN, 8% (<i>n</i> = 9) had DM, and 11% (<i>n</i> = 12) had both. Individuals with DM showed significantly lower FDs in the C5 partition of the deep vascular plexus (DVP), located 1.77 mm to 2.14 mm from the foveal center compared to controls without DM (1.57 ± 0.003 vs. 1.58 ± 0.006; <i>p</i> = 0.014). Those with both DM and HTN exhibited significantly lower FDs in the entire superficial vascular plexus (SVP) annulus (1.84 ± 0.01 vs. 1.85 ± 0.007; <i>p</i> = 0.006), as well as the C3 (1.58 ± 0.02 vs. 1.60 ± 0.02; <i>p</i> = 0.008), C4 (1.57 ± 0.002 vs. 1.57 ± 0.01; <i>p</i> = 0.036), C5 (1.56 ± 0.01 vs. 1.57 ± 0.008; <i>p</i> < 0.001), and C6 (1.58 ± 0.01 vs. 1.59 ± 0.008; <i>p</i> < 0.001) partitions of the SVP (1.03 mm to 2.50 mm from the foveal center) and the C4 (1.57 ± 0.008 vs. 1.58 ± 0.008; <i>p</i> = 0.015) and C5 (1.57 ± 0.01 vs. 1.58 ± 0.006; <i>p</i> = 0.012) partitions of the DVP (1.40 mm to 1.77 mm from the foveal center) compared to the controls with neither DM nor HTN. <b>Conclusions:</b> While our study examined FDs in a predominantly male veteran population, our findings align with prior studies that reported lower FDs in DM and HTN cohorts. Our study further localizes these microvascular changes, with the most prominent differences occurring at C5 and C6 of the SVP, representing an area between 1.77 and 2.50 mm from the center of the fovea. These data lay the groundwork for developing screening protocols to identify individuals at risk of developing vasculopathies.