Vestibular adaptation and substitution exercises will be performed by the experimental group (GS). Adaptation exercises involve head movement while maintaining focus on a target, which may be stationary or moving. Typical progression of adaptation exercises involve increased velocity of head movement, movement of both target and head, target placed in a distracting visual pattern and maintenance of a challenging posture. During active eye-head exercise, a large eye movement to a target is made prior to the head moving to face the target, potentially facilitating use of preprogrammed eye movements.

The placebo exercises will consist of saccadic eye movements while the head is stationary and will be performed by the control group. These eye movements will be performed against a plain background in order to eliminate retinal slip and, therefore, eliminate the error signal for vestibular adaptation.

As a result of their disequilibrium, subjects report decreased confidence that they can maintain their balance in a variety of situations. The Activities-specific balance confidence scale (ABC) was developed to measure the subject's confidence with their balance across a range of 16 activities of increasing challenge. Items are rated on a rating scale that ranges from 0 - 100% with a score of zero representing no confidence and a score of 100 representing complete confidence. An overall score is calculated by averaging the items with higher scores indicating higher (better) balance confidence.

This measure assesses walking speed over a short distance. Subjects were asked to walk at their preferred gait speed for a distance of 30 feet which allowed 5 feet for acceleration and deceleration at the beginning and end of the walk. The time it took to walk 20 feet was recorded using a calibrated stopwatch and gait speed (ft/s) was calculated.

Control group intervention includes standard balance rehabilitation plus placebo eye exercises.

Standard balance rehabilitation: All subjects perform balance and gait exercises in addition to eye exercises and receive a written home exercise program (HEP) of balance and gait exercises to improve postural stability and mobility. Walking for endurance is included in the HEP. Each participant receives a customized balance and gait HEP based on identified impairments and is progressed according to ability and level of assistance at home.

Control exercises: Placebo eye exercises consist of saccadic eye movements while the head is stationary. These eye movements are performed against a plain background in order to eliminate retinal slip and, therefore, eliminate the error signal for vestibular adaptation.

Total of all reporting groups

This scale was used to measure perceived level of dizziness after one minute of horizontal head movement at 1 Hz. This technique uses a 10-cm line with one end being no symptoms (score = 0) and the other representing the worse possible symptoms (score = 10) and is commonly used to assess perception of pain. The subject is asked to place a mark on the 10-cm line at a point which indicates the intensity of his/her perception of symptoms of dizziness and the distance along that line is measured. Scores range from 0 to 10 with higher scores indicating worse perceived dizziness.

This scale was used to measure perceived level of unsteadiness while walking. This technique uses a 10-cm line with one end being no symptoms (score = 0) and the other representing the worse possible symptoms (score = 10) and is commonly used to assess perception of pain. The subject is asked to place a mark on the 10-cm line at a point which indicates the intensity of his/her perception of symptoms of unsteadiness and the distance along that line is measured. Scores range from 0 to 10 with higher scores indicating worse perceived unsteadiness.

The dynamic gait index (DGI) assesses an individual's ability to modify balance while walking in the presence of external demands. The 8 items of the DGI include walking while changing speed and turning the head, walking over and around obstacles, and stair climbing. Scoring of the DGI is based on a 4-point scale from 0 to 3 with 0 indicating severe impairment and 3 indicating normal ability. A maximum total score of 24 is possible and scores of < 20 indicate high risk for falling.

As a result of their disequilibrium, subjects report decreased confidence that they can maintain their balance in a variety of situations. The Activities-specific balance confidence scale (ABC) was developed to measure confidence with balance across a range of 16 activities of increasing challenge. Items are rated on a rating scale that ranges from 0 - 100% with a score of zero representing no confidence and a score of 100 representing complete confidence. An overall score is calculated by averaging the items with higher scores indicating higher (better) balance confidence.

This measure assesses walking speed over a short distance. Subjects were asked to walk at their preferred gait speed for a distance of 30 feet which allowed 5 feet for acceleration and deceleration at the beginning and end of the walk. The time it took to walk 20 feet was recorded using a calibrated stopwatch and gait speed (ft/s) was calculated.

Control group (CON) intervention includes standard balance rehabilitation plus placebo eye exercises.

Standard balance rehabilitation: All subjects perform balance and gait exercises in addition to eye exercises and receive a written home exercise program (HEP) of balance and gait exercises to improve postural stability and mobility. Walking for endurance is included in the HEP. Each participant receives a customized balance and gait HEP based on identified impairments and is progressed according to ability and level of assistance at home.

Placebo eye exercises: Saccadic eye movements are performed while the head is stationary. These eye movements are performed against a plain background in order to eliminate retinal slip and, therefore, eliminate the error signal for vestibular adaptation.

This scale was used to measure perceived level of unsteadiness while walking. This technique uses a 10-cm line with one end being no symptoms (score = 0) and the other representing the worse possible symptoms (score = 10) and is commonly used to assess perception of pain. The subject is asked to place a mark on the 10-cm line at a point which indicates the intensity of his/her perception of symptoms of unsteadiness and the distance along that line is measured. Scores range from 0 to 10 with higher scores indicating worse perceived unsteadiness.

Repeated Measure (RM) ANOVA

The dynamic gait index (DGI) assesses an individual's ability to modify balance while walking in the presence of external demands. The 8 items of the DGI include walking while changing speed and turning the head, walking over and around obstacles, and stair climbing. Scoring of the DGI is based on a 4-point scale from 0 to 3 with 0 indicating severe impairment and 3 indicating normal ability. A maximum total score of 24 is possible and scores of < 20 indicate high risk for falling.

As a result of their disequilibrium, subjects report decreased confidence that they can maintain their balance in a variety of situations. The Activities-specific balance confidence scale (ABC) was developed to measure the subject's confidence with their balance across a range of 16 activities of increasing challenge. Items are rated on a rating scale that ranges from 0 - 100% with a score of zero representing no confidence and a score of 100 representing complete confidence. An overall score is calculated by averaging the items with higher scores indicating higher (better) balance confidence.

This measure assesses walking speed over a short distance. Subjects were asked to walk at their preferred gait speed for a distance of 30 feet which allowed 5 feet for acceleration and deceleration at the beginning and end of the walk. The time it took to walk 20 feet was recorded using a calibrated stopwatch and gait speed (ft/s) was calculated.

Control group (CON intervention includes standard balance rehabilitation plus placebo eye exercises.

Standard balance rehabilitation: All subjects perform balance and gait exercises in addition to eye exercises and receive a written home exercise program (HEP) of balance and gait exercises to improve postural stability and mobility. Walking for endurance is included in the HEP. Each participant receives a customized balance and gait HEP based on identified impairments and is progressed according to ability and level of assistance at home.

Placebo eye exercises: Saccadic eye movements are performed while the head is stationary. These eye movements are performed against a plain background in order to eliminate retinal slip and, therefore, eliminate the error signal for vestibular adaptation.