Peripheral Field Expension Device

Schepens Eye Research Institute
posted on 03/04/2009

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Stroke, head injury, tumors commonly cause peripheral vision loss in a condition called hemianopia. Various devices (mirrors, prism, reversed telescopes) have been considered to improve patient’s awareness of obstacles on their blind side and improve mobility but none were very effective. The “Peli System” of field expansion (the simultaneous seen field is larger with the device) involves a monocular sector prism that expends the field via peripheral diplopia and confusion. The new system shifts the field expansion property of peripheral prisms from the upper and lower peripheral visual fields toward the central visual field while maintaining the lateral field expansion. The image-shifting device does not interfere with the normal vision of the wearer and can be fitted onto one or both carrier lenses of a pair of spectacles. There are about 800,000 stroke survivors per year in the US, about a third have hemianopia.