A Standardized Obstacle Course for Assessment of Visual Function in Ultra Low Vision and Artificial Vision

Podsumowanie

We describe an indoor, portable, standardized course that can be used to evaluate obstacle avoidance in persons who have ultralow vision. The course is relatively inexpensive, simple to administer, and has been shown to be reliable and reproducible.

Streszczenie

We describe an indoor, portable, standardized course that can be used to evaluate obstacle avoidance in persons who have ultralow vision. Six sighted controls and 36 completely blind but otherwise healthy adult male (n=29) and female (n=13) subjects (age range 19-85 years), were enrolled in one of three studies involving testing of the BrainPort sensory substitution device. Subjects were asked to navigate the course prior to, and after, BrainPort training. They completed a total of 837 course runs in two different locations. Means and standard deviations were calculated across control types, courses, lights, and visits. We used a linear mixed effects model to compare different categories in the PPWS (percent preferred walking speed) and error percent data to show that the course iterations were properly designed. The course is relatively inexpensive, simple to administer, and has been shown to be a feasible way to test mobility function. Data analysis demonstrates that for the outcome of percent error as well as for percentage preferred walking speed, that each of the three courses is different, and that within each level, each of the three iterations are equal. This allows for randomization of the courses during administration.

Abbreviations:
preferred walking speed (PWS)
course speed (CS)
percentage preferred walking speed (PPWS)

Wprowadzenie

Low vision rehabilitation assessments must determine whether intervention results in improvement in function. Performance metrics typically involve computer based reading or functional assessments^1-9 as well as quality of life questionnaires^10-15. Being able to also assess the low vision patient's ability to navigate around obstacles might also provide clues to functional improvements¹⁸ particularly in the case of artificial vision devices. Geruschat et al. recently published navigation outcomes with a retinal implant chip, highlighting the need for a standard metric in this area¹⁷. Currently there are no widely accepted, objective, validated, and comprehensive standards for determining capacity for obstacle avoidance.

Development of a functional test that would correlate to navigation performance for persons with low vision or "ultra low vision" as produced by artificial vision would be desirable, but has remained an elusive goal. The burgeoning field of artificial vision devices such as retinal implant chips^18-24 or sensory substitution devices such as the BrainPort ²⁵ and The vOICe²⁶, necessitates a test of obstacle avoidance that might correlate to increased navigational abilities conferred by these devices. Such an assessment would not only allow subjects to understand their own limitations as they traverse their surroundings, but might provide a means for measuring improvement with orientation and mobility training or between iterations of vision enhancement prototype devices. Ideally, there might be some ability to assess an individual's risk for fall accidents²⁷.

Our goal was to create an obstacle course that would be useful for evaluation of navigation ability in patients using artificial vision devices and transferrable to the field of low vision in general. A review of the published literature on obstacle courses and visual impairment was undertaken using the PubMed database. There have been numerous attempts at creating standardized obstacle courses^{16,17,28-31,34}. Most of these are not portable in the sense that it would be difficult to exactly reproduce the setting, particularly for outdoor courses. Maguire et al. describe obstacle course which is used to show mobility performance in patients with Leber's Congenital Amaurosis. This course has the benefit of being portable and small, but it is not clear whether different iterations have been made available to prevent memorization effects, nor are there any provisions for obstacles which are not on the floor, texture changes, or stepovers. Leat provides an incisive description of potential pitfalls in designing a course and puts forth a description of an outdoor course which unfortunately would not be able to be reproduced exactly in an alternative location³⁰. Velikay-Parel et al. described a mobility test for use with retinal implant chips. This design had the benefit of being portable and simple to execute. While this course could be reproduced at an alternative site, no specific details on course construction are provided. Moreover, and more concerning was that they showed the learning effect reached asymptotic levels due to course familiarity, therefore being able to prevent course memorization altogether might eliminate the concern for loss of learning effect over time¹⁸. None of the courses described so far have been widely adopted by the low-vision or rehabilitation communities.

The authors subsequently consulted with a team of six low vision occupational therapists and orientation and mobility specialists from the Western Pennsylvania School for Blind Children (Pittsburgh, PA) and the Blind and Vision Services Rehabilitation of Pittsburgh (Homestead, PA) regarding proposed course design. Desirable attributes of a functional obstacle course identified included: Portability for easy assembly/disassembly and storage, flexibility to test under both dim and bright lighting conditions, and to mirror "real life" situations by including obstacles that represent objects in a patient's home environment that are sturdy enough to withstand repeated collision while being ductile in order to prevent patient injury. In addition it was deemed necessary to have several types of environments designed in such as way so that when administered in a randomized order prevents course memorization. In addition, the course should demonstrate reproducible results in multiple settings, have strong inter and intra rater reliability and be an objective measure of spatial awareness.

The culmination of this effort was development of an obstacle course which could reasonably be expected to be reproduced in a standard institutional hallway. The course is designed to test different skill sets, all important for navigation. Each level of the course attempts to focus several particular types of obstacles encountered in everyday navigation activities. The first course evaluates the ability to navigate through relatively high contrast targets that are all placed on the floor, but requires a large number of turns. The second course evaluates the ability to navigate through obstacles that are both high and low contrast, floor texture changes, and objects suspended in air. The final course evaluates the ability to navigate Styrofoam obstacles that are low contrast, surface glare changes on the floor, the addition of nonStyrofoam obstacles (fabric), floor tile color changes, obstacles that must be stepped over, and obstacles that are not on the floor. The courses are labeled 1, 2, and 3 for ease of labeling, but this designation should not be construed as increasing in level of difficulty. Within each level, there are three versions of the course, which can be randomized to prevent course memorization.

Protokół

1. Course Construction

1. Install course floor. Course dimensions are 40 ft long by 7 ft wide consisting of 280 1 ft² portable floor tiles (beige event floor tiles). Place with black trim around perimeter only (Figure 1).
2. Paint the adjacent walls to match the floor tiles creating a somewhat monochromatic environment. Colors we used with greyscale values are provided (Table 5). If the specific colors are not available, we recommend taking a tile to a hardware store for color matching.
3. Install lighting according to the lighting template (Figure 1). Connect lights to dimmer switch.
4. Paint obstacles according to painting instructions (Figure 2).

2. Prepare Testing Area

1. Adjust lighting to desired condition and check with light meter at the beginning, middle, and end of the hallway containing the course.
2. Make sure that the video camera is set to record and that placement of the camera is appropriate to capture the subjects as they walk through the course. We recommend a ceiling mount or alternatively the camera can be hand held.

3. Record Preferred Walking Speed PWS

1. Position subject in center of walkway (course column "D"). Note: toes should be behind border of walkway. Read instructions to the subject (Figure 3).
2. Begin stopwatch once foot crosses black border and onto pathway. Stop time once foot crosses black border at other end of walkway. Record time as PWS1. Turn subject around and repeat procedure in opposite direction. Record time as PWS2. Average PWS1 and PWS2 and record as final PWS.

4. Obstacle Course Navigation

1. From the randomization scheme, set up the first course (Figure 4). Floor tiles should be used as the grid upon which the obstacles are mapped. Refer to the provided diagram for correct mapping of the obstacles. It is helpful to number the tiles along the vertical and horizontal axis with an indelible marker to permit easy placement of the obstacles. It is also helpful to label the obstacles according to the provided diagrams in an inconspicuous location.
2. Guide subject to start of 40 ft walkway. Read instructions to the subject (Figure 3). Subject should be positioned in center of walkway (column "D") with toes behind border. Begin stopwatch once foot crosses black border and onto pathway. Stop time once foot crosses black border at other end of walkway. Record this time as Course Speed (CS).
3. Record when obstacles are hit, grading the severity of the hit on a 3 point scale. The course run should be videotaped for later confirmation by an independent observer.

5. Obstacle Identification

1. Upon completion of course navigation task, turn subject around to face the course and position at center of course (column D). Note: make sure that any obstacles that require repositioning in order to view correct color from end of course is rotated. Read instructions to subject (Figure 3). At this time the first object identification task will be administered. Ask the subject to turn around and tell the Research Assistant the total number of objects they can discern within 30 sec. This number should be recorded.
2. Tell the subject to walk back through the course and point to each obstacle they can see. It does not matter if they collide with the obstacle. The number of obstacles they can see is recorded. It is helpful to record which obstacles they are able to detect. This is not timed.

Items 4 and 5 should be repeated for each course version that is run.

Wyniki

Subjects

Six sighted blindfolded, sighted, and 36 completely blind but otherwise healthy adult (age range 19-85 years), male (n=29) and female (n=13) subjects were enrolled in one of three studies involving testing of the BrainPort sensory substitution device (Wicab, Madison WI). All studies were approved by the University of Pittsburgh IRB and all subjects signed an approved informed consent document. All studies were a within subjects, repeated measures design such that each subject acted as th...

Dyskusje

We describe an indoor, portable, easily reproducible, and relatively inexpensive course that can be used to evaluate obstacle avoidance in persons who are blind or have low vision. Most current obstacle course designs and tests (i.e. TUGS) are difficult to compare across sites and observers, or are permanent instillations which cannot readily be performed at alternate locations^16,17,30. Our goal was to create a course that could be standardized for use at different locations and with different observe...

Materiały

Name	Company	Catalog Number	Comments
Event Floor Tiles, beige	Snaplock Industries, Salt Lake City UT		Beige
Event Floor Tiles, black trim	Snaplock Industries, Salt Lake City UT		Male loop
Event Floor Tiles, black trim	Snaplock Industries, Salt Lake City UT		Female loop
Event Floor Tiles, Edging	Snaplock Industries, Salt Lake City UT		Black
Wall Paint: Satin Premium Plus Internal Satin Enamel Custom Color Match	Behr, Inc Santa Ana CA	custom	Greyscale value = 45
Obstacle paint	Valspar Paints, Wheeling, IL	DuJour (#70002-6)	DuJour Greyscale value = 15
Obstacle paint	Valspar Paints, Wheeling, IL	Fired Earth (#6011-1)	Fired Earth Greyscale value = 95
Styrofoam obstacles	Universal Foam Products, Orlando CA	custom
Con-Tact Brand Contact Paper	Lowe's Home Improvement	639982	Solid Black
Con-Tact Brand Contact Paper	Lowe's Home Improvement	615542	Stainless Steel
Con-Tact Brand Contact Paper	Lowe's Home Improvement	614416	Solid White
3 ft x 6 ft Standard tuff Olefin Floor Mat	Commercial Mats and Rubber A Division of Georgia Mills Direct Saratoga Springs, NY		Charcoal
3 ft x 6 ft Standard tuff Olefin Floor Mat	Commercial Mats and Rubber A Division of Georgia Mills Direct Saratoga Springs, NY		Smoke
Fisher Scientific Traceable Dual Range Light Meter	Fisher Scientific	06-662-63	International Light, Newburyport MA, USA
5 1/2 in Clamp Light	Lowe's Home Improvement	203198
GE 65-Watt indoor incandescent flood light bulb	Lowe's Home Improvement	163209