Oblique multi-periscopic prism for field expansion of homonymous hemianopia

Oblique Fresnel peripheral prisms have been used for field expansion in homonymous hemianopia mobility such as walking and driving. However, limited field expansion, low image quality, and small eye scanning range limit their effectiveness. We developed a new oblique multi-periscopic prism using a cascade of rotated half-penta prisms, which provides 42° horizontal field expansion along with 18° vertical shift, high image quality, and wider eye scanning range. Feasibility and performance of a prototype using 3D-printed module are demonstrated by raytracing, photographic depiction, and Goldmann perimetry with patients with homonymous hemianopia.