Despite advancements in the field of artificial vision, retinal prostheses continue to face substantial limitations. The future success of these devices depends on their ability to activate target neurons with improved spatiotemporal resolution, while avoiding off-target stimulation. Manually programming these devices in clinic using a trial-and-error process will place an excessive burden on both clinicians and patients. We applied the Taguchi method for design of experiments to patient-specific field-cable models of retinal prostheses to identify multi-electrode stimuli that focalize retinal activation, thus improving spatial resolution. We improved focality in all eight tested regions with a unique return electrode configuration, supporting the need for individualized current focusing strategies. This work lays the foundation for personalized, automated device programming, which will be essential for future retinal prostheses with thousands of electrodes.