User perspectives on the usefulness of prism glasses as a visual aid for people with Progressive Supranuclear Palsy

Introduction: This study examined how and why people with Progressive Supranuclear Palsy (PSP), a rare neurodegenerative disease associated with progressive gaze paralysis, use yoked ‘recumbent’ prism glasses.Method: Patients completed an online (N=65) or in-person (N=20) version of a Prism Use in PSP questionnaire.Results: 72.3% of patients had heard of prism glasses and 51% had tried them. The prism users were split into a group of yoked, recumbent users (N=27) and a group of peripheral prism users (N=10). 22% of recumbent prism users continued to use their glasses, compared to 60% of peripheral prism users. Only 17% recumbent prism users agreed that prism glasses were useful, whereas 62% disagreed or strongly disagreed. Patients with gaze paralysis in only 1 direction gave higher liking and usefulness ratings than those with more global oculomotor problems. Recumbent prisms were most frequently used when eating (33.1% of users) and reading (18%). At least one side effect was experienced by 41% of recumbent users, with disorientation the most common (34.6%). However, 23% of users reported no side effects. Weight and problems fitting over existing eyewear were the most commonly reported barriers to use. Discussion: Few people with PSP agreed that recumbent prisms were useful aids, suggesting they are not as helpful to patients as was previously thought, although there was some evidence for better success in patients with paralysis in only one gaze direction.Implications for Practitioners: Recumbent prism glasses are most likely to benefit people with PSP whose gaze paralysis is in one direction when eating and reading. However, weight and problems with fitting over existing glasses present significant barriers to use. Many users also experience disorientation, so practicing the desired task while wearing the glasses may be helpful. Recumbent prism glasses may be less beneficial patients with advanced gaze paralysis.