How Do Flanking Objects Affect Reaching and Grasping Behavior in Participants with Macular Disorders?

Purpose: To investigate how objects (flankers) placed on either side of a target affect reaching and grasping behaviour in visually impaired (VI) subjects due to macular disorders compared to age matched normals. Methods: Subjects reached out to grasp a cylindrical target placed on its own and when it had two identical objects (flankers) placed either half or one target diameter away on each side of the target. A motion analysis system (Vicon 460) recorded and reconstructed the 3D hand and finger movements. Kinematic data for transport and grasping mechanisms were measured. Results: In subjects with VI, crowding effected the overall movement duration, time after maximum velocity and maximum grip aperture. Maximum effect was shown when the flankers were placed close to the target (high level crowding) with a decreased effect shown for flankers placed further away (medium level crowding). Compared to normals, subjects with VI generally took longer to initiate the hand movement and to complete the movement. Time after maximum velocity and time after maximum grip aperture were also longer in subjects with VI. No interaction effects were found for any of the indices for the different levels of crowding in the two visual groups. Conclusions: Reaching and grasping behaviour is compromised in subjects with VI due to macular disorders compared to normals. Crowding affected performance for both normal subjects and those with VI. Flankers placed half an object diameter away showed greater deterioration than those placed further away

A Comparison of Reach-to-Grasp and Transport-to-Place Performance in Participants With Age-Related Macular Degeneration and Glaucoma

PURPOSE: To compare visually guided manual prehension in participants with primarily central field loss (CFL) due to age-related macular degeneration and peripheral visual field loss (PFL) due to glaucoma. This study extends current literature by comparing directly "reach-to-grasp" performance, and presents a new task of "transport-to-place" the object accurately to a new location. Data were compared to age-matched controls. METHODS: Three-dimensional motion data were collected from 17 glaucoma participants with PFL, 17 participants with age-related macular degeneration CFL and 10 age-matched control participants. Participants reached toward and grasped a cylindrical object (reach-to-grasp), and then transported and placed (transport-to-place) it at a different (predefined) peripheral location. Various kinematic indices were measured. Correlation analyses explored relationships between visual function and kinematic data. RESULTS: In the reach-to-grasp phase, CFL patients exhibited significantly longer movement and reaction times when compared to PFL participants and controls. Central field loss participants also took longer to complete the movement and made more online movements in the latter part of the reach. During the transport-to-place phase, CFL participants showed increased deceleration times, longer movement trajectory, and increased vertical wrist displacement. Central field loss also showed higher errors in placing the object at a predefined location. A number of kinematic indices correlated significantly to central visual function indices (P < 0.05). CONCLUSIONS: Significant differences in performance exist between CFL and PFL participants. Various indices correlated significantly with loss in acuity and contrast sensitivity (CS), suggesting that performance is more dependent on central visual function irrespective of underlying pathology

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

Diurnal Intraocular Pressure and the Relationship With Swept-Source OCT–Derived Anterior Chamber Dimensions in Angle Closure: The IMPACT Study

Purpose: To evaluate diurnal intraocular pressure (DIOP) among individuals with Primary Angle Closure (PAC) or Primary Angle Closure Suspect (PACS). Additionally the hypothesis that greater DIOP fluctuation is related to smaller angle parameters was investigated. Methods: 40 Caucasian newly referred untreated patients with bilateral PAC or PACS were recruited. Intraocular pressure (IOP) was measured hourly between 09.00 and 16.00 with Goldmann applanation tonometry. DIOP fluctuation was defined as difference between maximum and minimum IOP. Angle Opening Distance, AOD; Trabecular-Iris Angle (TIA); Angle Recess Area (ARA); Trabecular Iris Space Area (TISA) were measured with AS-OCT (CASIA) in dark (0.3-0.5 lux) and light (170-200 lux) on the same day as DIOP measurements in eight angle sections. Results: IOP declined as the day progressed (p<0.001), unrelated to presence of PAS. At each timepoint, eyes with PAS (n=31) had significantly higher IOPs than eyes without PAS (n=49; p=0.043). DIOP fluctuation varied from 1.50 mmHg to 14.50 mmHg (mean 5.99 mmHg, SD 2.70 mmHg). DIOP fluctuation was unrelated to PAS. Multiple-predictor models investigating association of angle dimensions and greater DIOP fluctuation were statistically significant for AOD 750 (light), ARA 750 (light and dark), TISA 500 (light), TISA 750 (light), TIA 500 (light) and TIA 750 (light and dark). Conclusions: DIOP variation has clinical implications given that IOP level is used to distinguish between diagnostic categories of PACS and PAC. OCT angle parameter measurements may predict for magnitude of IOP diurnal fluctuations in at-risk patients, which may be clinical useful when considering a clinical intervention

Ocular coherence tomography-measured changes over time in anterior chamber angle and diurnal intraocular pressure after laser iridotomy: IMPACT study

Importance: The change in the anatomical dimensions over time and the effect on diurnal intraocular pressure following laser peripheral iridotomy is poorly understood. Background: To evaluate change over time in anterior chamber angle anatomy following laser peripheral iridotomy (LPI) in patients with primary angle closure compared to control eyes. Additionally, the effect of LPI on diurnal intraocular pressure (DIOP) fluctuation was investigated. Design: Longitudinal, prospective, double-randomised research study. Participants: Adults with suspected angle closure or angle closure diagnosis referred to hospital services in the United Kingdom. Methods: Thirty-nine patients newly diagnosed with bilateral primary angle closure/suspects (PAC/PACS) received LPI to one eye and changes in angle morphology were measured over 8 sections with swept source AS-OCT. The other eye acted as control with intraocular pressure (IOP) measured hourly. Main outcome measures: Angle opening distance (AOD), trabecular–iris angle (TIA), angle recess area (ARA), and trabecular–iris space area (TISA) at 500 m and 750 m from scleral spur Results: There was an increase in all angle parameters following LPI, which was maintained for 6 months (e.g inferotemporal segment AOD500 0.041mm (p=0.008) at 1 week and 0.039mm (p=0.003) at 6 months) following LPI. Greatest effect at 6 months post-LPI was observed opposite the iridotomy site in the inferior/inferotemporal sections (AOD500 0.039mm, p=0.003 and AOD750 0.075mm, p=0.002). There were no statistically significant differences for the overall DIOP fluctuation values in the treated group at 6 months post-LPI compared to baseline. Conclusions and Relevance: LPI widened all angle sections with maximum effect observed in the site opposite the iridotomy. Angle changes were maintained up to 6 months after LPI treatment without any statistically significant change in DIOP fluctuation

Physical inactivity in relation to self-rated eyesight: Cross-sectional analysis from the English Longitudinal Study of Ageing

Background: To assess the cross-sectional association between self-rated eyesight and physical activity behaviour in a large general population sample of older English adults. Methods: Analyses of data from the English Longitudinal Study of Ageing. Participants provided information on self-rated eyesight (categorised as: excellent/ very good/ good/ fair-poor) and their own physical activity levels (categorised as: inactive/ moderate only at least 1/ week/ vigorous at least 1/ week). Associations between self-rated eyesight and physical activity levels were examined using logistic regression. Results: A total of 6,634 participants (mean age 65.0±9.2years) were included in the analyses. In adjusted logistic regression models those with fair-poor and good eyesight were significantly more likely to be inactive than those who reported excellent eyesight (OR 2.07, 95% CI 1.58, 2.72; OR 1.59, 1.27, 1.99, respectively). Conclusion: In this sample of older English adults, those with self-rated fair-poor vision were over twice as likely to be physically inactive than those who reported having excellent vision. When consistent data has emerged, interventions to increase physical activity in those who have poor eyesight are needed

How does aging influence object-location and name-location binding during a visual short-term memory task?

Objective: Age-related impairments in human visual short-term memory (VSTM) may reflect a reduced ability to retain bound object representations, viz., object form, name, spatial, and temporal location (so called ‘memory sources’). Our objective is to examine how healthy aging affects VSTM in a battery of memory recognition tasks in which sequentially presented objects, locations, and names (as auditory stimuli) were learned, with one component cued at test. Methods: Thirty-six young healthy adults (18-30 years) and 36 normally aging older adults (>60 years with no underlying health and vision issues) completed five VSTM tasks: 1. Object recognition for two or four objects; 2. Spatial location recognition for two or four objects; 3. Bound object-location recognition for two or four objects; 4. Object recognition with location priming for two or four objects; 5. Bound name (auditory)-location (cross-modal) recognition for four objects. Results: Significantly lower performance for older adults was found in spatial location recognition [task 2, p=0.03, 2 (memory loads) × 2 (age groups) ANOVA], bound object-location recognition [task 3, p˂0.001, 2 (memory loads) × 2 (age groups) ANOVA], object recognition with location priming [task 4, p=0.02, 2 (memory loads) × 2 (age groups) ANOVA], and bound name-location recognition [task 5, p=0.001, independent samples t-test] tasks. A significant age group-task interaction was found (p =0.02) Conclusion: Performance for all tests except test 1 was impaired in older adults. Lower performance for older adults was most significant in VSTM tasks requiring object-location (visual only) or name-location (auditory and visual) binding. The findings are compatible with the ‘memory source’ model, demonstrating that age-related binding performance is influenced by spatial coding and location priming deficits

The effects of temporal pressure on obstacle negotiation and gaze behaviour in young adults with simulated vision loss

Individuals with vision loss adapt their locomotion and gaze behaviour to safely negotiate objects in temporally unconstrained situations. However, everyday activities are often performed under time-pressure. We investigated the effects of blur on anxiety, movement kinematics and gaze behaviour during the negotiation of a floor-based obstacle under three amounts of pressure: 1) no-pressure; 2) tonal-pressure: an intermittent tone was played at a constant frequency; 3) tonal + time pressure: the intermittent tone increased in frequency and participants had to walk 20% faster to reach the end of the lab. Irrespective of the amount of pressure, the blurred vs. normal vision group reported 32% more anxiety, lifted the lead foot 43% higher and 10% slower over the obstacle, and looked 6% longer and 6% more frequently ahead of the obstacle. In the tonal + time pressure vs. no-pressure condition, both groups were more anxious, showed adaptations in movement kinematics related to walking faster, and adopted a ‘checking strategy’ by shortening their fixation durations at the obstacle. These results show that irrespective of temporal pressure, the blurred vision group remained more cautious as to how the lead foot negotiated the obstacle, in order to reduce the chance of tripping during crossing

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