Obstacle Negotiation in Older People With and Without Vision Impairment

Study Overview
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Brief Summary
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Falls are common among people with vision impairment and can lead to devastating health consequences. Understanding the functions of vision and how the visual characteristics of obstacles in the walking path impact the gait of people with vision impairment is necessary to create strategies to prevent falls in this population. The purpose of this study is to determine how adults with vision impairment change their gait behavior when stepping over obstacles that vary in height and contrast to the ground. We will then determine the mechanisms of gaze behavior that correlate to the gait behavior.

Official Title
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Impact of Stepping Over Obstacles of Different Contrast and Height on Gait and Eye Movements in Older Adults With and Without Vision Impairment

Conditions
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Low Vision

Intervention / Treatment
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* Other: Obstacle characteristics


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age 18 or over Able to walk independently Either have normal vision, or impaired vision. Impaired vision is defined as binocular visual acuity of 20/25 or worse with or without a central scotoma; and/or binocular visual field that is restricted to an average of 100 degrees in diameter or less Control subjects will have visual acuity of 20/40 or better. Exclusion Criteria: Not cleared by a medical provider for moderate physical activity Self-report or have a history of: vestibular disorder or deafness Medical history of any condition that affects the ability to walk for up to 2 hours with breaks, such as feeling dizzy or faint, chest pain, palpitations, pain or numbness in the legs, shortness of breath, Cognitive limitations either by self-report or a score on the Mini Mental State Exam below 24 (out of 30) Walking or gait abnormalities, such as those caused from an injury, surgery, severe arthritis, or neurological condition such as Parkinson's disease Unable to walk without any walking aids such as a walker, cane, guide dog, or oxygen tank. Does not speak English

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Low Vision Group<br>At a single study visit, the group of low vision participants will be asked to perform a series of short walking trials. During each trial they will walk at a self-selected speed along a walkway (6 meters in length) that may or may not contain an obstacle to step over. The trials will be randomly varied with regard to an obstacle's presence, height, and contrast from the walkway surface. Repeated trials of each condition variation will be performed during the visit. | Other: Obstacle characteristics<br>* In the walking trials, when an obstacle is present, the obstacle height and obstacle contrast level will be varied across the trial repetitions. Each participant will be exposed to obstacles of two heights: the first will be 1 centimeter in height, and the second will be approximately 20% of the subject's leg length (ranging in physical height between 15 - 22 centimeters to cover a range of leg lengths in the population). Obstacles (of both heights) will also be painted such that their measured luminance (or contrast) level against the floor luminance is varied. High contrast obstacles will have ≥80% Michelson contrast and low contrast obstacles will have ≤30% Michelson contrast.<br>|
| Active Comparator: Control Group<br>At a single study visit, the group of age-matched participants without low vision will be asked to perform a series of short walking trials. During each trial they will walk at a self-selected speed along a walkway (6 meters in length) that may or may not contain an obstacle to step over. The trials will be randomly varied with regard to an obstacle's presence, height, and contrast from the walkway surface. Repeated trials of each condition variation will be performed during the visit. | Other: Obstacle characteristics<br>* In the walking trials, when an obstacle is present, the obstacle height and obstacle contrast level will be varied across the trial repetitions. Each participant will be exposed to obstacles of two heights: the first will be 1 centimeter in height, and the second will be approximately 20% of the subject's leg length (ranging in physical height between 15 - 22 centimeters to cover a range of leg lengths in the population). Obstacles (of both heights) will also be painted such that their measured luminance (or contrast) level against the floor luminance is varied. High contrast obstacles will have ≥80% Michelson contrast and low contrast obstacles will have ≤30% Michelson contrast.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Vertical foot clearance, lead limb | Distance from lowest point of foot (heel or toe) to top of obstacle | During a single intervention visit (Study Visit 2), up to 2-3 hours in duration. | 
| Foot placement variability | Standard deviation of position of toe to obstacle over 2-4 steps before the obstacle | During a single intervention visit (Study Visit 2), up to 2-3 hours in duration. | 
| Obstacle crossing speed | Speed from lead toe off immediately before the obstacle to trail heel down immediately after the obstacle. | During a single intervention visit (Study Visit 2), up to 2-3 hours in duration. | 
| Gaze sequencing | Sequence of fixations from start of trial to end of trial, normalized to the total duration and divided into 100 equal segments | During a single intervention visit (Study Visit 2), up to 2-3 hours in duration. |