Difficulties With Goals of the Dutch ICF Activity Inventory: Perceptions of Those With Retinitis Pigmentosa and of Those Who Support Them

PURPOSE: To provide a comprehensive overview of the perceived difficulties with visual activities and participation by those with retinitis pigmentosa (RP), and as perceived by those who support people with RP. Further, to examine the performance of the Dutch ICF Activity Inventory (D-AI) using Rasch analysis. METHODS: Three hundred fifty people with RP and 75 supporters of people with RP provided demographic information and completed the D-AI at goal level (47 goals). RESULTS: Following removal of four goals, the D-AI behaved well in Rasch analysis, but with limitations to its unidimensionality. The most difficult goals for people with RP related to mobility and to work-related activities. Greater difficulty was associated with higher visual impairment registration status, use of mobility aids, and longer duration of visual impairment. For those with less severe visual loss, goals relating to communicating with people were relatively more difficult. In more severe loss, goals involving good central vision (e.g., dealing with correspondence) were relatively more difficult. The perceptions of supporters matched those of the people with RP relatively well, but with a tendency for supporters to overestimate the difficulty of goals, which related to administration and domestic chores, and to underestimate difficulty with goals relating to communication with people. CONCLUSIONS: The results indicate important areas of rehabilitation to address in addition to orientation and mobility in those with RP, including work-related activities and goals involving good central vision. Both people with RP and those supporting them could benefit from help addressing difficulties with communication

Relative Difficulties of Daily Living Tasks with Retinitis Pigmentosa

Purpose: To determine the relative difficulty of activity of daily living tasks for people with retinitis pigmentosa (RP). Methods: Participants with RP (n = 166) rated the difficulty of tasks (n = 43) underpinning the Dutch Activity Inventory goals of mobility indoors and outdoors, shopping, and using public transport. Demographic characteristics were also determined. Responses were Rasch analyzed to determine properties of the scale, derive unidimensional subscales, and consider differential item functioning (DIF). Results: After removal of one ill-fitting item, the remaining 42 tasks formed a scale with reasonable Rasch parameters but poor unidimensionality. The most difficult tasks were orienting in poor and bright light both indoors and outdoors, and avoiding peripheral obstacles outdoors. Eight subscales were derived with unidimensional properties, each of which could be considered as requiring similar skills. DIF identified that tasks from the “poor light and obstacles” subscale were more difficult for those younger than the median age, nonusers of mobility aids, and those not registered or registered sight impaired. Tasks from the “finding products” and “public transport” subscales were more difficult for those older than the median age, with longer duration of visual loss, users of mobility aids, and those registered severely sight impaired. Conclusions: The most difficult tasks for people with RP of orienting in poor light and avoiding peripheral obstacles are relatively more difficult for those not registered as “severely sight impaired,” but are less difficult for those who use mobility aids. Mobility aids (guide dog or cane), therefore, do benefit users in their perceived ability in these particular tasks. The derived unidimensional subscales reorganize the tasks from those grouped together by goal (researcher driven) to those perceived as requiring similar skills by people with RP (patient driven) and can be used as an evidence base for orientation and mobility training protocols

Visual Search Behavior in Individuals With Retinitis Pigmentosa During Level Walking and Obstacle Crossing

Purpose: Investigate the visual search strategy of individuals with retinitis pigmentosa (RP) when negotiating a floor-based obstacle compared with level walking, and compared with those with normal vision. Methods: Wearing a mobile eye tracker, individuals with RP and normal vision walked along a level walkway or walked along the walkway negotiating a floor-based obstacle. In the level walking condition, tape was placed on the floor to act as an object attracting visual attention. Analysis compared where individuals looked within the environment. Results: In the obstacle compared with level walking condition: (1) the RP group reduced the length of time and the number of times they looked Ahead, and increased the time and how often they looked at features on the ground (Object and Down, P < 0.05); and (2) the visual normal group reduced the time (by 19%) they looked Ahead (P = 0.076), and increased the time and how often they looked at the Object (P < 0.05). Compared with the normal vision group, in both level walking and obstacle conditions, the RP group reduced the time looking Ahead and looked for longer and more often Down (P < 0.05). Conclusions: The RP group demonstrated a more active visual search pattern, looking at more areas on the ground in both level walking and obstacle crossing compared with visual normals. This gaze strategy was invariant across conditions. This is most likely due to the constricted visual field and inability to rely on inferior peripheral vision to acquire information from the floor within the environment when walking

The effect of Retinitis Pigmentosa on activities of daily living

The majority of previous research investigating the impact of low vision on the completion of activities of daily living (ADLs) have examined visual impairment as a whole. The aim of this thesis was to provide a comprehensive overview of ADLs to determine what the most difficult areas are for people with Retinitis Pigmentosa (RP), a particular type of visual impairment. This research was achieved through both self-report questionnaire and objective analysis of human movement. 681 participants (570 with RP) were examined throughout this research. Identified through self-report, at the objective level, the most difficult ADLs amongst those with RP was mobility. In particular, at the goal level, this was identified as mobility outdoors (experimental chapter 1). Further, at the task level, orientation and walking around safely without bumping into things and tripping over or stepping off something were identified as most difficult (experimental chapter 2). Those who support people with RP perceived most of the ADLs significantly more difficult to complete (for those with RP), with greatest difference in perceptions between two groups being practical tasks. When assessing balance through measuring postural control (experimental chapter 3), those with RP showed similar postural control to those with normal vision when standing on a firm surface, regardless of the vision condition (eyes open or eyes closed). However, when standing on a foam surface with eyes open, the reduction in postural control among people with RP, compared to those with normal vision, highlighted the added importance of the somatosensory information to maintaining standing balance for those with RP. However, it was only apparent when the somatosensory system was disturbed. The examination of gait among people with RP (experimental chapter 4) demonstrated that those who used a mobility cane adopted a cautious walking behaviour in both level walking and obstacle crossing tasks. Such cautious behaviour was not evident for people with RP who did not use a cane, or for the normally sighted individuals. This thesis is the first to provide a comprehensive overview of self-report difficulties among those with RP. Findings also demonstrate the importance of maintaining adequate foot (somatosensory) and eye (vision) health for those with RP to regulate balance control. The additional mobility training for those with RP who use a cane is necessary for their walking gait. Furthermore, the support from the carers should reflect the needs of those with RP, which helps them with their independence in completing ADLs rather than overprotecting them