Compared with conventional radiation techniques, proton therapy provides highly conformal dose distributions while reducing irradiation of surrounding normal tissues. Combining proton beams with different energies generates an extended Spread-Out Bragg Peak (SOBP) to cover the target. Passive scattering uses a range modulator wheel (RMW) to adjust proton energy and broaden the Bragg peak. In this study, a proton therapy nozzle comprising an RMW, compensator, and collimators was simulated for ocular tumor treatment using the GATE Monte Carlo code. A three-dimensional computational eye phantom including the lens, aqueous humor, cornea, choroid, retina, sclera, vitreous body, optic nerve, and tumor was developed to evaluate ocular dose distributions. The designed RMW generated a relatively uniform SOBP with a target length of 3.0 mm, a distal dose gradient (DDF) of 0.9 mm, and a d90 of 21.5 mm. The tumor dose was normalized to 100%, while relative doses were 52% for the lens, 63% for the aqueous humor, 62% for the cornea, 60% for the retina, 51% for the choroid, 44% for the sclera, 67% for the vitreous body, and 1% for the optic nerve. The results indicate that the RMW and compensator produced the intended SOBP and localized dose distribution within the modeled tumor geometry. These findings demonstrate the potential of the proposed nozzle configuration for achieving target-specific dose distributions while limiting irradiation of critical ocular structures. The developed computational framework provides a useful platform for investigating ocular proton-nozzle design and treatment-planning strategies.