TAcute Effects of Standardized Cervical Flexion on Intraocular Pressure, Choroidal Thickness, and Peripapillary Capillary Density: A Prospective Self-Controlled Study

INTRODUCTION: Cervical flexion is a common posture in modern life, yet its acute effects on ocular hemodynamics are unknown. This study evaluates the acute effects of standardized cervical flexion on intraocular pressure (IOP), choroidal thickness (CT), and optic nerve head microvasculature in healthy adults.
METHODS: This prospective, controlled study was conducted with 80 healthy volunteers (mean age 26.8±3.1 years). IOP, multi-point CT (EDI-OCT), and OCTA parameters [radial peripapillary capillary (RPC) density and foveal avascular zone (FAZ) area] were measured in neutral seated position and after 5 minutes of 45-60° cervical flexion.
RESULTS: Cervical flexion induced significant IOP increase in both eyes (Right: +1.9±0.8 mmHg, p = 0.001; Left: +1.8±0.9 mmHg, p = 0.001). Significant thinning was observed in most choroidal regions, most notably subfoveally (-13.2±18.7 µm, p = 0.003), while the temporal location (p = 0.011) showed a trend not meeting Bonferroni correction. RPC density reduction (-1.3±1.8%, p = 0.012) is close to reported test-retest variability (25). FAZ area remained unchanged (p = 0.874). IOP increase was greater in emmetropic than myopic participants (p = 0.028). A negative correlation was found between IOP increase and subfoveal CT reduction (r = -0.41, p = 0.001).
DISCUSSION AND CONCLUSION: Brief cervical flexion causes acute IOP elevation, choroidal thinning, and reduced peripapillary capillary density. These findings underscore the importance of postural standardization in IOP assessment and reveal an acute hemodynamic stress pathway associated with neck-flexed posture.

Keywords: Cervical flexion, Intraocular pressure, Choroidal thickness, OCT angiography, Posture, Hemodynamics