Initial investigations are aimed at determining the suitability of the patient for proton beam radiotherapy, estimating the likely outcomes, and planning treatment. The benefits and risks of all the therapeutic options are discussed.7 The tumor size and location are defined by slit-lamp examination and/or ophthalmoscopy as well as by color photography and ultrasonography. Secondary effects of the tumor on the eye, such as retinal detachment, are identified in addition to any unrelated, concurrent ocular disease. The axial length of the eye is measured to enable a computerized, 3D model of the eye to be generated. This is done using the EyePlan system developed at Clatterbridge.