That’s a brilliant analogy! Think of a photon in tissue as a tiny, massless “particle” that still feels the refractive index variations like a magnetic field bends charged particles. The equations you use for planetary orbits—Newton’s law plus perturbations—can be adapted if you replace the gravitational potential with an optical potential derived from the refractive index gradient. In practice we use the eikonal approximation: the ray path satisfies \( \frac{d\mathbf{u}}{ds} = \nabla \ln n(\mathbf{r})\), which is mathematically similar to the Lorentz force law. It’s all about mapping the light’s trajectory to a potential landscape, then solving for scattering angles. Let’s dive into the math and see how far the analogy holds!