Abstract Body (Do not enter title and authors here): Introduction
Atenolol is a widely prescribed beta-blocker for managing systemic hypertension, but its potential impact on ocular microvasculature remains poorly understood. Investigating these effects may support more informed treatment decisions for patients with coexisting cardiovascular and ocular conditions.

Methods
BPH/2J mice, an established model of neurogenic hypertension driven by elevated sympathetic tone, were administered atenolol (3 mg/kg/day) via drinking water over two months. Retinal and limbal vasculature were imaged in vivo using visible-light optical coherence tomography angiography (vis-OCTA) (Fig. 1a). Compared with established OCT operating within the near-infrared spectral range, vis-OCT provides a three-fold improvement in spatial resolution and higher sensitivity in motion contrast in small vessels. For anterior imaging, a robotic arm with 6 degrees of freedom was used to acquire eight 45° field-of-view scans for a full 360° view of the limbus. Vascular remodeling was assessed by quantifying vessel diameter and fractal dimension from en-face angiograms. Image processing and structural analysis were performed using custom MATLAB scripts and ImageJ plugins.

Results
Vis-OCTA revealed significant remodeling of the limbal vasculature in atenolol-treated BPH/2J mice. After two months of treatment, limbal vessel diameter increased to 14.80 ± 1.23 μm compared to 11.57 ± 0.94 μm in controls (p < 0.01), accompanied by a rise in fractal dimension from 1.317 ± 0.062 to 1.450 ± 0.044 (p < 0.05) (Fig. 1b). In contrast, retinal vasculature exhibited only modest changes, with vessel diameter increasing from 7.60 ± 0.38 μm in controls to 8.25 ± 0.66 μm in the atenolol group (p = 0.09), and a slight elevation in fractal dimension from 1.953 ± 0.005 to 1.960 ± 0.005 (p = 0.07) (Fig. 1c). Reductions in systolic, diastolic, and mean arterial pressure were observed, confirming the systemic efficacy of atenolol.

Conclusions
Despite not being a direct vasodilator, our findings suggest that atenolol induces structural remodeling in the ocular microvasculature. Compared to the retina, the more pronounced changes observed in limbal vessels may reflect regional differences in adrenergic regulation. Moreover, the degree of limbal remodeling showed a weak but measurable correlation with blood pressure reduction (R² = 0.35), suggesting that anterior segment vessels may serve as a noninvasive marker of individual responsiveness to systemic beta-blocker therapy.