Clinical Trial of Peripheral Prism Glasses for Hemianopia

Not Applicable

Completed

Conditions: Homonymous Hemianopia

Interventions: Device: High power (57 prism diopter) peripheral prism glasses
Device: Low power sham peripheral prism glasses

Registration Number: NCT00494676

Lead Sponsor: Alexandra Bowers

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 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.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 73

Inclusion Criteria

At least 18 years of age.
Sighted in both eyes, with monocular visual acuity (best corrected vision), of at least 20/50 in each eye.
Complete homonymous hemianopia of more than 3 months duration
Refractive error within the -5 dioptre to +5 dioptre range
No significant cognitive impairment
No history of wearing the Peli system of peripheral prisms for hemianopic field expansion (patients who have worn another type of prismatic correction for hemianopia such as yoked prisms or the Gottlieb VAS system can participate in the study)
No physical or mental disabilities, including cognitive dysfunction, balance problems or other deficits that could impair ability to walk or use the peripheral prism spectacles.
Able to walk (using a cane or walker is OK) or control the movements of their own wheelchair.
In sufficiently good health to attend four in-office visits.

Exclusion Criteria

Diagnosis of dementia
Diagnosis of visual neglect
History of seizures in the last 6 months
Incomplete hemianopia

Study & Design

Study Type: INTERVENTIONAL

Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Real prism glasses first, then sham	Low power sham peripheral prism glasses	Participants in this arm will receive high power (57 prism diopter) peripheral prism glasses in the first period of the crossover and low power sham peripheral prism glasses in the second period
Real prism glasses first, then sham	High power (57 prism diopter) peripheral prism glasses	Participants in this arm will receive high power (57 prism diopter) peripheral prism glasses in the first period of the crossover and low power sham peripheral prism glasses in the second period
Sham prism glasses first, then real	Low power sham peripheral prism glasses	Participants in this arm will receive low power sham peripheral prism glasses in the first period of the crossover and high power (57 prism diopter) peripheral prism glasses in the second period
Sham prism glasses first, then real	High power (57 prism diopter) peripheral prism glasses	Participants in this arm will receive low power sham peripheral prism glasses in the first period of the crossover and high power (57 prism diopter) peripheral prism glasses in the second period

Primary Outcome Measures

Name	Time	Method
Overall Proportion Saying "Yes" to Real Prism Glasses	Evaluated after 4 weeks of wearing each type of prism glasses	At the end of each crossover period, participants were asked a yes/no question: "If the study were to end today, would you want to continue with these prism glasses (i.e. the prism glasses worn in that period)?" The primary outcome was the overall difference, across the two periods of the crossover, between the proportion of participants saying "yes" to real prism glasses and the proportion saying "yes" to sham prism glasses.

Secondary Outcome Measures

Name	Time	Method
Mobility Change Score (All Participants Who Completed Crossover)	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)	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)	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).

Trial Locations

Locations (13): Emory Optical Low Vision
🇺🇸
Atlanta, Georgia, United States
Indiana University School of Optometry, Low Vision Rehabilitation and Primary Care Services
🇺🇸
Bloomington, Indiana, United States
Schepens Eye Research Institute
🇺🇸
Boston, Massachusetts, United States
Vista Center for the Blind and Visually Impaired
🇺🇸
Palo Alto, California, United States
Illinois Eye Institute
🇺🇸
Chicago, Illinois, United States
NSU Oklahoma College of Optometry,
🇺🇸
Tahlequah, Oklahoma, United States
UAB Center for Low Vision Rehabilitation
🇺🇸
Birmingham, Alabama, United States
Visual Health@Jupiter Eye Center
🇺🇸
Jupiter, Florida, United States
Academy Eye Associates
🇺🇸
Durham, North Carolina, United States
Vision Care Specialists, P.C.
🇺🇸
Southborough, Massachusetts, United States
Manchester Royal Eye Hospital
🇬🇧
Manchester, United Kingdom
Seven Lakes Eye Care
🇺🇸
West End, North Carolina, United States
University of Kansas Medical Center
🇺🇸
Prairie Village, Kansas, United States