Anticipatory action planning in blind and sighted individuals

Measuring visually guided motor performance in ultra low vision using virtual reality

Introduction

Ultra low vision (ULV) refers to profound visual impairment where an individual cannot read even the top line of letters on an ETDRS chart from a distance of 0.5 m. There are limited tools available to assess visual ability in ULV. The aim of this study was to develop and calibrate a new performance test, Wilmer VRH, to assess hand-eye coordination in individuals with ULV.

Methods

A set of 55 activities was developed for presentation in a virtual reality (VR) headset. Activities were grouped into 2-step and 5-step items. Participants performed a range of tasks involving reaching and grasping, stacking, sorting, pointing, throwing, and cutting. Data were collected from 20 healthy volunteers under normal vision (NV) and simulated ULV (sULV) conditions, and from 33 participants with ULV. Data were analyzed using the method of successive dichotomizations (MSD), a polytomous Rasch model, to estimate item (difficulty) and person (ability) measures. MSD was applied separately to 2-step and 5-step performance data, then merged to a single equal interval scale.

Results

The mean ± SD of completion rates were 98.6 ± 1.8%, 78.2 ± 12.5% and 61.1 ± 34.2% for NV, sULV and ULV, respectively. Item measures ranged from -1.09 to 5.7 logits and - 4.3 to 4.08 logits and person measures ranged from -0.03 to 4.2 logits and -3.5 to 5.2 logits in sULV and ULV groups, respectively. Ninety percent of item infits were within the desired range of [0.5,1.5], and 97% of person infits were within that range. Together with item and person reliabilities of 0.94 and 0.91 respectively, this demonstrates unidimensionality of Wilmer VRH. A Person Item map showed that the items were well-targeted to the sample of individuals with ULV in the study.

Discussion

We present the development of a calibrated set of activities in VR that can be used to assess hand-eye coordination in individuals with ULV. This helps bridge a gap in the field by providing a validated outcome measure that can be used in vision restoration trials that recruit people with ULV, and to assess rehabilitation outcomes in people with ULV.

The effects of visual impairment on motor imagery in children and adolescents

BACKGROUND

While the development of motor imagery (MI) has been extensively studied in sighted children, it is not clear how children with different severities of visual impairment (VI) represent motor actions by using the motor representations constructed through the remaining intact senses, especially touch.

AIMS

Mental chronometry and generation/manipulation of MI were examined in children with and without VI.

METHODS AND PROCEDURES

Participants included 64 youth with and without VI (33 without visual impairments, 14 moderate-to-severe, and 17 blind). Mental chronometry was assessed with the imagined Timed-Up-and-Go-Test (iTUG), and generation/manipulation of MI with the Controllability-of-Motor-Imagery-Test (CMI). In addition, the effect of working memory performance (Letter-Number-Sequencing) and physical activity upon MI were evaluated.

RESULTS

Mental duration for the iTUG was significantly shorter than the active durations. Results also provided evidence of better haptic representation than motor representation in all participants; however, only for the CMI-regeneration condition controls outperformed children with visual impairments and blindness (CVIB). Exercise and working memory performance showed a significant contribution only on a few MI tests.

CONCLUSION AND IMPLICATIONS

Our results suggest a possible relationship between motor performance, body representation deficits and visual impairment which needs to be addressed in the evaluation and treatment of CVIB. The design of new rehabilitation interventions that focus on strengthening adequate body perception and representation should be proposed and tested to promote motor development in CVIB.