Astrophysical plasma environments and quantum-gravity-inspired spacetime regularization collectively modify photon dynamics near compact objects, yet their coupled impact on photon sphere structure remains unquantified. This study examines the photon sphere radius ( $r_{\mathrm{ph}}$ ) for static Hayward regular black holes immersed in a cold, non-magnetized plasma with a power-law density profile ( $\omega _{p}^{2} \propto r^{-k}$ ). The modified condition for circular photon orbits, incorporating the regularization parameter $l$ and plasma strength $K$ , was numerically solved across physical parameter ranges. Results demonstrate a consistent inward shift of $r_{\mathrm{ph}}$ relative to the Schwarzschild vacuum case, with individual increases in $l$ (to $1.0M$ ) or $K$ (to 0.5) reducing $r_{\mathrm{ph}}$ by up to $12.7\%$ and over $18\%$ , respectively. Crucially, combined effects exhibit nonlinear synergy: the contraction exceeds additive expectations, peaking at $l \approx 0.8M$ and $K \approx 0.3$ with a residual shift $\Delta r_{\mathrm{ph}}/M \approx -0.32$ and a total shift $\delta r_{\mathrm{ph}}^{\mathrm{total}}/M \approx -0.32$ for typical accretion parameters ( $k = 1.5$ ). This synergy, arising from the combined amplification by plasma gradients and quantum-corrected curvature, enhances sensitivity to plasma strength by $60\%$ compared to singular geometries. The corresponding 4– $12\%$ reduction in black hole shadow diameter underscores the significance of these interactions for interpreting next-generation interferometric observations of strong-gravity lensing features.
