Influence of Fermi surface geometry and Van Hove singularities on the optical response of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>Sr</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mi>RuO</mml:m

Motivated by the sensitivity of ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}$ to Fermi surface reconstructions under strain, we investigate how Fermi surface geometry and Van Hove singularities influence the optical Hall response and polar Kerr effect. Within a three-orbital model, we explore the impact of chemical potential and interlayer hopping on superconducting pairing and response functions. We find that ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ and ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}+ig$ symmetries are the leading candidates for the quasi-two-dimensional (quasi-2D) orbital, while a chiral $p$-wave state in quasi-1D orbitals is essential for generating an accessible Kerr angle. The Lifshitz transition is shown to affect coherence factors and density-of-states peaks, producing sharp signatures in ${T}_{c}$ and optical transport. Interorbital charge transfer further enhances these effects by modifying the balance between the contributions of the quasi-1D and quasi-2D orbitals. These results provide a framework for interpreting Kerr effect experiments in multiorbital superconductors.