Quantitative Changes in Iris Vessel Area Density During Valsalva Maneuver in Healthy Eyes

Purpose: To quantify changes in iris vessel area density (VAD) during the Valsalva maneuver (VM) and explore their associations with anterior segment parameters in healthy subjects. Methods: This prospective cross-sectional study included 82 healthy volunteers, with one eye randomly selected for analysis. Iris VAD was quantified at baseline and during VM using optical coherence tomography angiography. Anterior segment parameters and intraocular pressure (IOP) were also assessed under both conditions. Results: Compared to baseline, significant reductions in total iris VAD were observed during VM (P = 0.029), with more pronounced decreases in the inner and outer iris regions (both P < 0.010). Concurrently, VM led to a significant elevation in IOP (P < 0.001), reductions in anterior chamber depth (P = 0.020) and volume (P < 0.001), and an increase in crystalline lens rise (P = 0.004). During VM, smaller values were observed in scleral spur angle (SSA500, P = 0.006; SSA750, P = 0.002), angle opening distance (AOD500, P = 0.014; AOD750, P = 0.001), anterior chamber angle (ACA750, P = 0.013), and trabecular-iris space area (TISA750, P = 0.004). Regression analysis revealed that axial length (AL), changes in TISA750, and changes in lens thickness were associated with VM-induced iris VAD changes (all P < 0.05). Conclusions: VM reduced iris microcirculation in healthy individuals, particularly in those with shorter AL, accompanied by structural anterior segment changes. Translational Relevance: This study provides microvascular evidence of VM-induced iris hypoperfusion and suggests that hemodynamic mechanisms contribute to anterior segment alterations during VM.