HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Geruschat, D. R. Articles by Turano, K. A. Search for Related Content PubMed PubMed Citation Articles by Geruschat, D. R. Articles by Turano, K. A.

Estimating the Amount of Mental Effort Required for Independent Mobility: Persons with Glaucoma

¹From the Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and the ²Maryland School for the Blind, Baltimore, Maryland.

PURPOSE. To validate the use of the secondary-task method to estimate the amount of mental effort required for independent travel and to determine how the amount of mental effort varies with characteristics of the environment.

METHODS. Reaction time (RT) to a secondary task (randomly presented vibrations) was obtained in 28 persons with glaucoma as they walked in four different environments: hallway, high-pedestrian area, approach-to-stairs area, and stairs. Cronbach's was used to assess the reliability of the secondary-task RT measures from the split-half measures of the high-pedestrian area. The construct validity of the RT measures as an estimate of mental effort was assessed by (1) the association between the RT scores and the item measure scores for similar environments derived from a Rasch analysis of perceived difficulty ratings obtained in a separate group of 83 persons with glaucoma and (2) the association between the RT scores and the severity of visual field loss.

RESULTS. Reliability was supported by a Cronbach's coefficient of 0.89. Construct validity was also supported by the data: (1) Log RT scores were linearly related to the Rasch analysis item measures for comparable mobility situations (P = 0.008), and (2) the log RT, averaged across the four environments, was linearly related to the mean deviation score of the Humphrey Visual Field Analyzer (estimate of visual field loss; P = 0.003; Carl Zeiss Meditec, Inc., Dublin, CA). A comparison of the log RT scores obtained in the four environments showed significantly higher log RT scores in the stairs area than in the high-pedestrian and hallway environments, whereas the log RT scores in the high-pedestrian and hallway environments were not significantly different.

CONCLUSIONS. The findings in this study demonstrate the reliability and construct validity of the secondary-task RT measure as an estimate of the amount of mental effort required to travel independently. It is sensitive to environmental characteristics and the loss in a walker's visual field. The method could be an objective way to document those who may benefit from professional intervention and to evaluate the effectiveness of an intervention.