Individuals with visual field loss report collisions with other pedestrians or objects and are commonly not permitted to drive. All of these factors severely restrict their independence and quality of life. Various visual aids developed for field expansion to detect collision in mobility but had limited success. The novel concept of vision multiplexing by shifting, combined with binocular visual confusion, has been a proven effective aid for patients with homonymous hemianopia. This approach uses peripheral unilateral prisms (prisms on one eye) and thus shows a shifted view from the blind field in the eye with the prism while the fellow eye sees the normal view. With binocular visual confusion, patients with homonymous hemianopia sees both shifted view and normal view together and achieve true field expansion using unilateral prisms. However, this approach results in the rivalry between two different views from two eyes, which alternates and reduce the detection performance in half. To overcome this limitation, we invented a new optical element, multiplexing prism, which provides simultaneous (monocularly) superimposed views of the shifted and direct see-through fields of view. Bilateral fitting of multiplexing prisms (prisms on both eyes) shows both shifted and see-through views in each eye and thus may reduce the binocular rivalry and provide three-dimensional information of shifted and see-through views. However, as a trade-off, the contrast of each view is reduced in half. Here, we will study the impact of these factors on the collision detection in field expansion of patients with homonymous hemianopia using virtual reality walking simulator and find the best configuration with less rivalry. The multiplexing prism is also the only possible field expansion solution for patients with acquired monocular vision. Losing sight of an eye is one of the common field loss in the US and increase the risk of collision with other pedestrians from the nasal side of the seeing eye. Since the multiplexing prism provides both see-through and shifted views simultaneously, fitting the multiplexing prism on the nose bridge provides recover of the visual field up to 90, which recovers almost normal binocular visual field size. Here we propose to implement, tune, and test the effectiveness of the multiplexing prism as an aid for patients with acquired monocular vision and develop a hang-on multiplexing prism glasses for easy wearing/taking off. We will test the device in a clinical trial with virtual reality walking simulator.
Visual confusion is the core mechanism for field expansion in patients with field loss to detect collision in mobility. Collision detection performance with binocular visual confusion using unilateral peripheral prisms is reduced by binocular rivalry, and thus we develop new monocular visual confusion devices. We will reveal the visual mechanism of monocular visual confusion with considering contrast reduction, providing stereoscopic depth cues, and coherency of motion flows and study the impact in the field expansion of patients with homonymous hemianopia using head-mounted displays and of patients with acquired monocular vision using multiplexing prism.
