NCT00494676

Clinical Trial of Peripheral Prism Glasses for Hemianopia

Community-based Multi-center Randomized Control Trial of Peripheral Prism Glasses for Hemianopia

• Status: Completed
• Phase: N/A
• Study type: Interventional
• Enrollment: 73 (actual)
• Sponsor: Alexandra Bowers · Academic / Other
• Sex: All
• Age: 18 Years
• Healthy volunteers: Not accepted

Summary

The purpose of this study is to evaluate the functional utility for general mobility (walking) of new high power permanent peripheral prism glasses, which provide visual field expansion device for patients with homonymous hemianopia (the complete loss of half the field of vision on the same side in both eyes). The efficacy of real peripheral prism glasses will be assessed relative to sham peripheral prism glasses.

Detailed description

Patients with hemianopic field loss are unaware of objects in their blind (non-seeing) hemi-field and often experience difficulties with mobility and navigation, such as walking into obstacles on the side of the field loss. In 2000, Peli (2000) described a new peripheral-prism design of prismatic correction for hemianopia, which addresses many of the inadequacies of existing designs of hemianopic visual aids, and produces true field expansion (i.e. the simultaneously seen field is larger with the device than without). In collaboration with the Schepens Eye Research Institute (Boston, MA), Chadwick Optical Inc (White River Junction, VT) has developed a permanent form of Fresnel prism segments, which are made from an acrylic material and can be embedded in a plastic spectacle lens. These permanent prisms offer better cosmesis, optical quality and durability than the temporary 40 prism-diopter press-on Fresnel prism segments used in previous evaluations of the peripheral prism system. In this study we will evaluate new high-power (57 prism diopter) permanent peripheral prism glasses. The study will employ a crossover design in which each participant will wear a pair of real prism glasses (high-power, 57 prism diopter) and a pair sham prism glasses (low-power, 5 prism diopters, that provide little field expansion) in counterbalanced order. The efficacy of the real prism glasses relative to the sham prism glasses will be assessed for general mobility (walking). We expect that participants will prefer the real prism glasses over the sham prism glasses as the former will be more helpful for obstacle detection when walking. Prism glasses will be fitted by Low Vision Practitioners at community-based Vision Rehabilitation Clinics. After wearing the first pair of glasses for 4 weeks, participants will return for an in-office follow up visit, at which a questionnaire will be administered to record their experiences of wearing the glasses. The second pair of prism glasses will then be fitted. Another questionnaire will be administered 4 weeks later to record the experiences of wearing the second set of glasses. At the end of the period of wearing the second pair of prism glasses, a clinical decision will be made as to whether the participant should continue to use the real prism glasses (e.g. if a participant finds the prism glasses helpful for obstacle avoidance when walking). For participants who continue with the prism glasses, a final telephone follow-up interview will be conducted after about 6 months.

Conditions

• Homonymous Hemianopia

Interventions

Type	Name	Description
DEVICE	High power (57 prism diopter) peripheral prism glasses	All patients will wear two pairs of prism glasses in a crossover design: the high power peripheral prism glasses and sham peripheral prism glasses. Each pair of prism glasses will be worn for four weeks
DEVICE	Low power sham peripheral prism glasses	Low power (5 prism dioptre) prism glasses that provide only about 2 degrees of visual field expansion.

Timeline

• Start date: 2007-09-01
• Primary completion: 2009-07-01
• Completion: 2010-04-01
• First posted: 2007-07-02
• Last updated: 2017-04-04
• Results posted: 2013-09-13

Locations

13 sites across 2 countries: United States, United Kingdom