Optical Prism Designs Expands Vision Field for the Sight-Impaired

BOSTON, May 24, 2016 — A series of novel optical designs may address the limitations of current peripheral prism eyeglasses and help further expand the field of vision for patients with hemianopia, a condition in which the visual fields of both eyes are cut in half.
Current high power prism segments embedded in a regular spectacle lens can expand the upper and lower visual fields of patients by as much as 30°. However, this technology does not expand the central area of the visual field.


By embedding the current prism in a spectacle lens that has prismatic power in the opposite direction, the image shifting effect is increased by the summation of the power of both prism types. This design allows for up to 36° of expansion to the visual field on the patient’s blind side. This design permits 5° of scanning range to the blind side with full effect. Courtesy of Massachusetts Eye and Ear.


With the goal of increasing the visual field provided by current technology, researchers from the Schepens Eye Research Institute of Massachusetts Eye and Ear and Harvard Medical School explored new optical techniques to create even higher power image shifting devices designed to bend the light farther than the 30° limit of conventional prisms. They developed, implemented and tested three novel eyeglass designs aimed at increasing the prism power to reduce the central gap in the vision field while maintaining wide lateral expansion.
One design involved inserting the peripheral prisms into carrier lenses that included yoked prisms in the opposite directions. By embedding the current prism in a spectacle lens that had prismatic power in the opposite direction, the image shifting effect increased by the summation of the power of both prism types. This design allows for up to 36° of expansion to the visual field on the patient’s blind side and permits five degrees of scanning range to the blind side.
A second design involved the use of bi-part double Fresnel prisms. Two Fresnel segments are combined, attached at the base and angled to each other to increase the power of the peripheral prism. This design allows for up to 43° of expansion to the visual field on the patient’s blind side and an increase to 14° of scanning range to the blind side……..
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Source: Photonics Media

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