Application of Rasch Analysis to Timed Instrumental Activities of Daily Living in Low Vision: A Validation Study.

SIGNIFICANCE: This work validates Rasch analysis of a performance-based low vision outcome measure evaluated in patients' own homes to ensure real-world relevance. Inclusion of sources of variance from the patient's home environment in functional outcome measures introduced nonuniform variance in measurements but did not preclude estimation of valid measures. PURPOSE: This study aimed to validate Rasch analysis of a performance-based outcome measure with real-world relevance. METHODS: Low vision patients (N = 161) receiving services from an occupational therapist performed Timed Instrumental Activity of Daily Living (TIADL) tasks in their homes. Rasch analysis was applied to error count and performance time data. Internal validity was assessed with evaluations of the accuracy and precision of estimated measures. External validity was assessed by comparing TIADL measures with measures estimated from the Activity Inventory (i.e., from self-reported difficulty ratings). RESULTS: Task measures were well targeted to person measures estimated from task performance time but were poorly targeted for measures estimated from task performance errors, for which most task trials (72%) were performed without error at baseline. Error-based person measures had larger standard errors with a smaller pseudo- R2 than time-based person or task measures and error-based task measures. Person measure infits for time- and error-based estimates conformed to expected values. The linear regressions between time-based person and task measures and corresponding error-based estimates had slopes of approximately 0.5, an observation consistent with larger estimation error variance for error-based measures than for time-based measures. Time-based TIADL person measures ( x ) and Activity Inventory person measures (estimated from all items, y ) were colinear but weakly correlated ( R = 0.19). CONCLUSIONS: Functional ability measures estimated from performance times of instrumental activity of daily living tasks in patients' homes demonstrate good internal and external validity. The ceiling effect from the infrequency of task performance errors in our data set limits use of TIADL error data to measure rehabilitation outcomes.

Utilization and Abandonment of Low Vision Devices Prescribed on a Mobile Clinic.

SIGNIFICANCE: Device utilization and abandonment for patients seen on a mobile clinic are explored. Findings are informative for resource allocation in a novel low vision rehabilitation (LVR) delivery model. This study also explores the relationships between device abandonment and LVR patient-reported functional outcomes. PURPOSE: This prospective cohort study investigated low vision device utilization and abandonment in a novel mobile clinic delivery model. METHODS: A device abandonment questionnaire was administered by telephone 3 months and 1 year after mobile clinic LVR. Participants (n = 65) had previously met the U.S. definition of legal blindness and were prescribed a total of 154 devices at their low vision consultative visits. Trends in device utilization and correlations with clinical and demographic participant characteristics, as well as functional outcomes as assessed by Massof Activity Inventory, are explored. RESULTS: An average of 2.6 device recommendations were made per participant. Digital magnification, optical magnifiers, and filters were most frequently recommended. At 3 months, 29% of participants abandoned at least one device, although only 17% of received devices were abandoned. There was no significant difference in the number of devices used, abandoned, or not received at 3 months versus 1 year after LVR. Devices prescribed for reading goals were most frequently used and least often abandoned, whereas glare control and distance magnification devices were more frequently abandoned. Neither patient characteristics nor Massof Activity Inventory change score was predictive of device abandonment. There was no significant difference in the odds of device abandonment in comparison with a previous study that assessed academic outpatient LVR clinics using the same questionnaire. CONCLUSIONS: Although more device recommendations are given per patient on the mobile clinic, there is no significant difference in device abandonment for patients seen on the mobile clinic versus other outpatient LVR delivery models.