Clinical Trial: Clinical Trial of Peripheral Prism Glasses for Hemianopia

Study Status: Completed
Recruit Status: Completed
Study Type: Interventional

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

Brief 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 Summary:

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 u
Sponsor: Alexandra Bowers

Current Primary Outcome: Overall Proportion Saying "Yes" to Real Prism Glasses [ Time Frame: Evaluated after 4 weeks of wearing each type of prism glasses ]

Original Primary Outcome:

• Clinical success: the proportion of participants fitted with each type of prism glasses for whom the clinical decision is to continue using the glasses (i.e. participants who find the glasses helpful for obstacle avoidance when walking). [ Time Frame: Evaluated after 4 weeks of wearing each type of prism glasses ]
• Rating of how helpful each type of prism glasses are in avoidance of obstacles when walking [ Time Frame: Evaluated after 4 weeks of wearing each type of prism glasses ]

Current Secondary Outcome:

• Mobility Change Score (All Participants Who Completed Crossover) [ Time Frame: Evaluated after 4 weeks of wearing each type of prism glasses ]
  Perceived difficulties with mobility were quantified using a 5-point rating scale (no difficulty to extreme difficulty) for 7 situations (items) relevant to people with hemianopia, including at home, in stores, outdoors, in unfamiliar areas, in familiar areas, in crowded areas, and noticing objects off to the side when walking. The questionnaire was administered at baseline (without prisms) and after each period of the crossover. Interval scale measures of perceived difficulty with overall mobility for each participant were estimated using Rasch analysis of the responses to all seven items (Winsteps software, version 3.70.0.226). Rasch measures were expressed as logits (log odds ratios). Mobility change scores for real and sham prisms were defined as the difference in perceived difficulty relative to baseline (in logits).
• Mobility Change Score (Only Participants Who Continued Prism Wear in the Long Term) [ Time Frame: Evaluated after 4 weeks of wearing each type of prism glasses ]
  Perceived difficulties with mobility were quantified using a 5-point rating scale (no difficulty to extreme difficulty) for 7 situations (items) relevant to people with hemianopia, including at home, in stores, outdoors, in unfamiliar areas, in familiar areas, in crowded areas, and noticing objects off to the side when walking. The questionnaire was administered at baseline (without prisms) and after each period of the crossover. Interval scale measures of perceived difficulty with overall mobility for each participant were estimated using Rasch analysis of the responses to all seven items (Winsteps software, version 3.70.0.226). Rasch measures were expressed as logits (log odds ratios). Mobility change scores for real and sham prisms were defined as the difference in perceived difficulty relative to baseline (in logits).
• Mobility Change Score (Only Participants Who Discontinued Prism Wear in the Long Term) [ Time Frame: Evaluated after 4 weeks of wearing each type of prism glasses ]
  Perceived difficulties with mobility were quantified using a 5-point rating scale (no difficulty to extreme difficulty) for 7 situations (items) relevant to people with hemianopia, including at home, in stores, outdoors, in unfamiliar areas, in familiar areas, in crowded areas, and noticing objects off to the side when walking. The questionnaire was administered at baseline (without prisms) and after each period of the crossover. Interval scale measures of perceived difficulty with overall mobility for each participant were estimated using Rasch analysis of the responses to all seven items (Winsteps software, version 3.70.0.226). Rasch measures were expressed as logits (log odds ratios). Mobility improvement scores for real and sham prisms were defined as the difference in perceived difficulty relative to baseline (in logits).

Original Secondary Outcome:

• Ratings of mobility difficulties in various situations without and with each type of prism glasses [ Time Frame: Evaluated at baseline and after 4 weeks of wearing each type of prism glasses ]
• Long-term clinical success: proportion of participants fitted with each type of prism glasses who continue to use and find them helpful for mobility after 6 months [ Time Frame: Evaluated 6 months after the clinical decision to continue with the prism glasses ]

Dates:
Date Received: June 28, 2007
Date Started: September 2007
Date Completion:
Last Updated: April 1, 2017
Last Verified: April 2017