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Community-Based Trial of a Peripheral Prism Visual Field Expansion Device for Hemianopia
Alex R. Bowers, PhD;
Karen Keeney, MSBA;
Eli Peli, MSc, OD
Arch Ophthalmol. 2008;126(5):657-664.
Objective To determine the functional utility for general mobility of peripheral prism glasses, a novel visual field expansion device for hemianopia, in a large-scale, community-based, multicenter study with long-term follow-up.
Methods Forty-three participants with homonymous hemianopia were fitted with temporary press-on Fresnel peripheral prism segments of 40 prism diopters. Follow-up questionnaires evaluating functional benefits for mobility were administered in the office at week 6. Participants who continued wearing the prisms were interviewed again by telephone after a median of 12 months. Primary outcome measures included clinical success (a clinical decision to continue wear) and 5-point ratings of prism helpfulness for obstacle avoidance when walking.
Results Thirty-two participants (74%) continued prism wear at week 6, and 20 (47%) were still wearing the prisms after 12 months (median time, 8 hours per day). These participants rated the prism glasses as very helpful for obstacle avoidance and reported significant benefits for obstacle avoidance in a variety of mobility situations. Success rates varied among clinic groups (27%-81%), with higher rates at the clinics that fitted more patients.
Conclusion Our results demonstrate the functional utility of peripheral prism glasses as a general mobility aid for patients with hemianopia.
Author Affiliations: Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts (Drs Bowers and Peli); and Chadwick Optical, Inc, White River Junction, Vermont (Ms Keeney).
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