This thesis develops MRI-based methods for treatment planning and longitudinal characterization of uveal melanoma in proton beam therapy. It combines anatomical, quantitative, and dynamic contrast-enhanced MRI to assess tumor morphology and perfusion before and after treatment. The results demonstrate that MRI enables accurate tumor measurements and clinically relevant follow-up, including in challenging post-intervention settings. The work establishes MRI biomarkers that support personalized planning and response assessment in ocular oncology.