Homonymous Hemianopia
Conditions
Keywords
Hemianopia, Mobility, Rehabilitation, Low vision
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.
Interventions
DEVICEHigh 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
DEVICELow power sham peripheral prism glasses
Low power (5 prism dioptre) prism glasses that provide only about 2 degrees of visual field expansion.
Sponsors
Chadwick Optical Inc.
National Eye Institute (NEI)
Alexandra Bowers
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
TREATMENT
Masking
DOUBLE (Subject, Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| 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
| Measure | Time frame | Description |
|---|---|---|
| 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). |
Countries
United Kingdom, United States
Participant flow
Recruitment details
Participants were recruited at 13 study sites, including Dr. Peli's lab at Schepens, 11 vision rehabilitation clinics in the US, and one in the UK. The clinics included university, hospital and private-practice clinics. Each site recruited a median of 7 participants (range 3 to 12). Data were collected in the period October 2007 to January 2010.
Pre-assignment details
97 subjects were screened for eligibility of which 73 met the study criteria and were enrolled. The main reasons for not meeting the inclusion criteria were incomplete hemianopia and spatial neglect.
Participants by arm
| Arm | Count |
|---|---|
| Entire Study Population Includes groups allocated to receive real prism glasses first and sham prism glasses first | 73 |
| Total | 73 |
Withdrawals & dropouts
| Period | Reason | FG000 | FG001 |
|---|---|---|---|
| Allocation | Withdrawal by Subject | 2 | 4 |
| First Intervention | Withdrawal by Subject | 1 | 3 |
| Second Intervention | Withdrawal by Subject | 1 | 1 |
Baseline characteristics
| Characteristic | Entire Study Population |
|---|---|
| Age, Continuous | 56 years STANDARD_DEVIATION 16 |
| Duration of hemianopia | 18 Months |
| Sex: Female, Male Female | 26 Participants |
| Sex: Female, Male Male | 47 Participants |
| Side of hemianopia Left hemianopia | 48 Participants |
| Side of hemianopia Right hemianopia | 25 Participants |
Adverse events
| Event type | EG000 affected / at risk |
|---|---|
| deaths Total, all-cause mortality | — / — |
| other Total, other adverse events | 0 / 67 |
| serious Total, serious adverse events | 0 / 67 |
Outcome results
Primary
Overall Proportion Saying Yes to Real 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.
Time frame: Evaluated after 4 weeks of wearing each type of prism glasses
Population: Only participants who completed the crossover were included in this analysis
| Arm | Measure | Group | Value (NUMBER) |
|---|---|---|---|
| Entire Study Population | Overall Proportion Saying Yes to Real Prism Glasses | Said yes to real prism glasses | 39 participants |
| Entire Study Population | Overall Proportion Saying Yes to Real Prism Glasses | Said yes to sham prism glasses | 22 participants |
Comparison: The analysis used a McNemar test for data combined across both periods of the crossover. We estimated that 70% and 35% of participants would say yes to the real and sham prisms, respectively. For a 2-tailed test, the minimum sample size to detect a 35% difference in yes responses to real and sham prisms was 57 participants, assuming 30% overlap (30% said yes to both pairs of glasses), power of 90% and α of 1%. Assuming an attrition rate of 20%, we planned to enroll 68 participants.p-value: =0.00195% CI: [1.8, 21]McNemar
Secondary
Mobility Change Score (All Participants Who Completed Crossover)
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).
Time frame: Evaluated after 4 weeks of wearing each type of prism glasses
Population: Only participants who completed the crossover were included in this analysis
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Entire Study Population | Mobility Change Score (All Participants Who Completed Crossover) | Mobility change score for real prisms | 1.9 logits | Standard Deviation 3.3 |
| Entire Study Population | Mobility Change Score (All Participants Who Completed Crossover) | Mobility change score for sham prisms | 1.3 logits | Standard Deviation 2.5 |
Comparison: Mobility improvement scores were normally distributed. A paired t-test was used to conduct a within-subjects comparison of the crossover differences in mobility scores between real and sham prism glasses. An alpha level of 5% was used to indicate statistical significance for secondary analysesp-value: =0.0995% CI: [-0.1, 1.3]t-test, 2 sided
Secondary
Mobility Change Score (Only Participants Who Continued Prism Wear in the Long Term)
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).
Time frame: Evaluated after 4 weeks of wearing each type of prism glasses
Population: This is a subgroup analysis of the mobility change scores for real and sham prism glasses evaluated during the crossover. The subgroup includes only those participants who completed the crossover and continued to wear prism glasses in the long term.
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Entire Study Population | Mobility Change Score (Only Participants Who Continued Prism Wear in the Long Term) | Mobility change score for real prisms | 3.0 logits | Standard Deviation 3.2 |
| Entire Study Population | Mobility Change Score (Only Participants Who Continued Prism Wear in the Long Term) | Mobility change score for sham prisms | 1.1 logits | Standard Deviation 2.4 |
p-value: =0.00295% CI: [0.7, 3]t-test, 2 sided
Secondary
Mobility Change Score (Only Participants Who Discontinued Prism Wear in the Long Term)
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).
Time frame: Evaluated after 4 weeks of wearing each type of prism glasses
Population: This is a subgroup analysis of the mobility change scores for real and sham prism glasses evaluated during the crossover. The subgroup includes only those participants who completed the crossover and then discontinued wearing prism glasses.
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Entire Study Population | Mobility Change Score (Only Participants Who Discontinued Prism Wear in the Long Term) | Mobility change score for real prisms | 1.1 logits | Standard Deviation 3.3 |
| Entire Study Population | Mobility Change Score (Only Participants Who Discontinued Prism Wear in the Long Term) | Mobility change score for sham prisms | 1.6 logits | Standard Deviation 2.7 |
p-value: =0.2195% CI: [-1.2, 0.3]t-test, 2 sided