We explore the lattice dielectric properties of strongly anharmonic rutile TiO2 using first principles anharmonic lattice dynamics methods. We employ the modified self-consistent approach, including third and fourth-order anharmonicity to accurately determine the \(\Gamma \) point phonon frequencies crucial for evaluating optical properties. The calculated optical phonon frequencies and linewidths at the \(\Gamma \) point show much closer agreement with experimental measurements than those obtained through perturbative methods. Notably, We show that the four-phonon scattering process contributes as much as the third-order anharmonic term to phonon linewidths of some phonon modes. Analysis of the frequency dependence of phonon linewidths further unveils that experimentally observed but unidentified peaks in the dielectric function can be attributed to two-phonon processes. These findings highlight the critical role of the selfconsistent approach in predicting the optical properties of materials with strong anharmonicity.