Technological solution for the assessment and rehabilitation of visuo-cognition in Parkinson’s disease

1. Background

Parkinson’s disease (PD) commonly affects both visual and cognitive functions, which is complicated by the fact that these functions are inter-related (termed visuo-cognition). Visuo-cognitive deficits range from impairments in basic visual functions (i.e. acuity and contrast sensitivity) to higher levels of visual attention and perception. Studies have shown that people with PD are more likely to experience visual impairments, and these impairments are associated with an increased risk of hip fracture, depression, anxiety, dementia, and hallucinations [1]. Furthermore, visuo-cognitive dysfunction is associated with freezing of gait in PD, which is one of the most common reasons for falls and dependency in this population [2].

Accurate and timely diagnosis of visuo-cognitive impairments is important in PD, as early intervention could prevent loss of independence and reduce falls risk. In practice, visuo-cognitive function is assessed using pen and paper outcome measures or eye charts, which can be subjective (based on expert rating), time-consuming and only examine global function. Visuo-cognitive function is rarely considered for rehabilitation in PD, with limited studies using eye movement exercises, pen and paper tasks, or inter-active games to improve visuo-cognitive performance. There is a need for a more objective technological approach that can comprehensively assess and provide rehabilitation for visuo-cognitive deficits in PD.

Here, we present the package of visuo-cognitive tools offered by Senaptec Ltd., a company who have developed a series of digital technologies that can be deployed with healthy and clinical populations to assess and rehabilitate visuo-cognitive function (https://senaptec.com/). We discuss how this technology may offer a solution to address the need for faster diagnosis of, and targeted intervention for, visuo-cognitive deficits in PD.

1. Senaptec visuo-cognitive technology

1.1. Using the senaptec sensory station

The Senaptec Sensory Station (SSS) is a computerized tool designed to evaluate and train visuo-cognitive function [3–5]. It is an interactive touch screen device consisting of a computer that controls two LCD monitors mounted on a height adjustable pedestal (Figure 1a). The station runs on an Android operating system and uses cloud-based technology to manage data and create user profiles and progress reports for each individual.

Figure 1. a. Senaptec Sensory Station; b. Senaptec Strobe Glasses operated via buttons at side of glasses or remotely via a mobile application; c. Senaptec Application; d. Radar chart.

There are a variety of visuo-cognitive impairments in PD that require a comprehensive assessment battery, which the SSS has the potential to provide. The SSS assessment includes demographic information, as well as vision correction and medical history. Individuals complete a battery of 10 computerized tasks that are administered with video instructions. The interactive task battery includes measures such as acuity, contrast sensitivity and depth perception, as well as tasks that rely on visuo-cognitive and motor function such as reaction time, perception span, and multiple-object tracking. Tasks are performed at close range (2 feet) on the main screen or via a smartphone interface for training at a distance (10 feet). The visuo-cognitive assessments in the SSS have been validated against reference measures in healthy populations [3]. Additionally, test–retest reliability on the SSS has been demonstrated in healthy individuals, with no significant differences between repeated assessments [6].

1.2. Intervention with senaptec technology

1.2.1. Strobe/quad strobe glasses

People with PD (and older adults) become increasingly reliant on visuo-cognition for mobility, which may require sensory reweighting training to overcome functional problems and improve performance. Stroboscopic visual perturbation has been shown to be a valid assessment method for sensory dependence and reweighting [7]. In addition to offering the SSS, Senaptec produce glasses which have liquid crystal lens technology that allows the lenses to strobe between clear and opaque (Figure 1b). These glasses block visual information intermittently during fully mobile tasks and have been used in a variety of sporting and clinical contexts as a means of training visuo-cognitive abilities and improving motor performance.

The strobe frequency and pattern (Table 1) can be controlled from the side of the glasses (using two buttons) or remotely using the accompanying mobile application (Figure 1b), so a patient or clinician can control the visual input received during tasks and allow progressions to be made during rehabilitation. The lens mode settings can be customized according to which aspects of vision are being trained. For example, one lens can remain strobing, while the other lens remains opaque, which allows targeted training of a non-dominant eye or peripheral vision. The Quad Strobe lenses are divided into four segments which allow different regions of the lens to be activated (or occluded). This modification may be of particular use in conditions such as stroke or multiple sclerosis where visual field deficits are more common.

Table 1. Strobe levels, settings.

Strobe Levels
Level	Frequency (Hz)	Clear (sec)	Opaque (sec)
1	6	0.1	0.067
2	5	0.1	0.100
3	4	0.1	0.150
4	3	0.1	0.233
5	2.25	0.1	0.344
6	1.75	0.1	0.471
7	1.33	0.1	0.650
8	1	0.1	0.900
Strobe and Quad Strobe Pattern Settings
Lens Mode	Setting Description		Training target
A	Both lenses strobing		Standard (default) mode for all round training and therapy.
B	Left lens strobing, right lens opaque		To block central vision and focus brain on peripheral vision.
C	Right lens strobing, left lens opaque
D	Lower vision blocked both lenses		Ball handling drills.
E	Upper vision blocked both lenses		To encourage head up for posture and balance control.
F	Right lower and left upper quadrant vision blocked		Targeted visual field/quadrant training
G	Left lower and right upper quadrant vision blocked
H	Alternating between right and left lenses strobing and opaque
I	Left upper quadrant strobing, remaining quadrants opaque.
J	Right upper quadrant strobing, remaining quadrants opaque.
K	Strobing alternating between different quadrants.
Training Module	Description
Eye-hand co-ordination	Find and touch the targets quickly and accurately.
Go / No-Go	Touch the ‘Go’ targets before they disappear, but do not touch the ‘No-Go’ target.
Dynamic Vision	Move your eyes to follow the target on the screen.
Perception Training	Symbols appear briefly, requiring the user to quickly see information in both central and peripheral vision.
Response Inhibition	Go targets and no-go targets appear momentarily in a single location. Touch the go target before it disappears and do not touch the no-go targets.
Spatial Memory	A set of targets appear momentarily on the screen. After they disappear, touch the screen in the locations the targets appeared.
Spatial Sequence	Targets appear and disappear sequentially. Touch the screen in the same location and order as the targets appeared.
Multiple Object Tracking	Move the dot to avoid collisions with the multiple objects that are moving around the screen.
Depth Perception	Put on red/blue glasses and stand 6 meters from the display. The center circle is on the same depth plane as only one of the four outer goals. Use the Senaptec Remote App on a mobile phone to swipe in the direction to put the circle in the goal in the same plane.
Near Far Shift	Stand 6 meters away from the display while holding Senaptec Remote App. Three directional symbols will appear. On the Remote App, swipe in the direction that two of the three symbols face. Task switches between the far display and the mobile phone with every response.
Visual Search	Find and touch the single target amongst the distractors.
Tempo	Maintain rhythm by touching the target with each beat.
Shape Cancellation	Find and touch all the targets but do not touch the distractors.
Visual-Motor Integration	Draw on the touch screen with your finger to repeat the pattern, either by tracing or looking at an adjacent shape.
Split Attention	Respond to a constantly changing task at the center of the screen while at the same time, respond to peripheral targets appearing on the rest of the screen.

1.2.2. Senaptec application

Home-based and patient-centered rehabilitations that can be undertaken by patients without clinicians needing to be present are needed for PD. The ‘Senaptec App’ is a portable training extension of the SSS assessment/rehabilitation, which can be used on a tablet within any environment and works on both Android and iOS platforms (Figure 1c).

The Senaptec App uses algorithms to automatically increase the difficulty of the training in line with subject performance, which reduces the need for clinical input into rehabilitation progression. The data and algorithm are synchronized with an onlline hub, which is a secure cloud-based technology to manage the data and provide results during the rehabilitation program. This can be remotely accessed by clinicians to monitor adherence and progression. The App includes 15 training modules aimed at targeting different aspects of visuo-cognitive and visuo-motor function, such as eye-hand co-ordination, depth perception, and multiple-object tracking.

1.3. Senaptec solution outcomes/reports

The Sensory Performance report is presented on a radar chart that provides a simple summary of overall performance (Figure 1d). The further the score from the center of the chart, the better the performance in that area of sensory function. The summary provides a percentile ranking to show specific patient strengths and areas for improvement. The report is available immediately upon completion of the evaluation, and raw data can be downloaded for further analysis or research, with the specific metrics for the assessments (e.g. LogMar scores).

1.4. Use of Senaptec solutions for clinical assessment and intervention

The Senaptec solutions have been used with healthy young individuals and more recently, within clinical populations for assessment and rehabilitation of visuo-cognitive function. Studies on healthy individuals have shown that visuo-cognitive outcomes can predict real-world task performance, such as goal scoring ability in hockey players [4] and collision avoidance in football players [8]. Additionally, the use of Strobe Glasses as an intervention/training tool has been shown to improve eye-hand co-ordination, sensory weighting, and attentional capabilities in healthy populations [7,9,10].

In terms of clinical populations, assessment using the SSS has highlighted visuo-cognitive deficits following neurological injury, specifically concussion in sport and military populations [11,12], with links to subsequent mobility impairment [13]. SSS outcomes have been found to improve with stroboscopic visual training in those with concussion, with modifications in underlying brain activity [14]. As a result, the SSS is often used as a baseline measure of visuo-cognitive performance prior to neurological injury [11]. Older adults and those with neurological diseases have also benefited from stroboscopic visual training. For example, older adults and people with multiple sclerosis have been shown to benefit even within a single session of rehabilitation [15,16]. Stroboscopic visual training has also been found to be useful for musculoskeletal injuries, such as anterior cruciate ligament injury, with balance improvements resulting from sensory perturbation during rehabilitation [17]. These clinical applications demonstrate that technologies such as the Senaptec solution show promise for use within a variety of settings and within a range of populations in the future, including PD.

2. Future work

In 2020, Senaptec Ltd. and Northumbria University formed a collaboration to develop a clinical study to examine the feasibility and initial efficacy of using the Senaptec solutions in individuals with PD. The study is currently underway and involves 40 people with PD undergoing either standard care or the Senaptec technological visuo-cognitive training (TVT) over a 4-week period [18]. All participants are assessed using the SSS pre- and post-intervention, and those in the TVT arm use the strobe glasses and Senaptec App for home-based rehabilitation twice per week with a physiotherapist. The clinical study will take 36 months to complete, with subjects recruited from the Northumbria Healthcare NHS Foundation Trust and the Gateshead Health NHS Foundation Trust. If the findings demonstrate that the Senaptec solutions are useful for visuo-cognitive assessments and rehabilitation in PD, this would support their use as a potential means of objectively and comprehensively providing visuo-cognitive care for patients in a variety of settings.

Longer term randomized trials are needed to determine whether use of this platform leads to a sustained improvement in visuo-cognitive outcomes in both healthy individuals and those with neurological diseases. In PD specifically, studies should explore the role of Senaptec technology in those with freezing of gait. Further work is also required to determine the feasibility of integrating these Senaptec tools into existing health-care practices, taking into account costs, user-acceptability and current clinical practices.

Beyond the scope of the ongoing study, we envisage that the Senaptec solutions could be useful for disease progression monitoring and may aid in early diagnostics of PD. Other areas of potential use would be drug development pipelines, where response to medication or deep brain stimulation may be objectively measured. These applications would greatly improve the care of people with PD.

3. Summary

The technical feasibility of the Senaptec solutions for visuo-cognitive assessment and rehabilitation has been established in healthy and clinical populations. Work is underway to assess the use of these solutions with PD, which may prove to provide a time-efficient and user-friendly tool that can be used by non-experts (even patients) to diagnose and rehabilitate visuo-cognitive impairment.

Declaration of interest

Julia Das is funded by a Northumbria University PhD studentship in collaboration with Senaptec Ltd (Beaverton, Oregon, USA) as well as a Movement Disorder Research Grant from the British Geriatric Society. Samuel Stuart is funded in part by a Parkinson’s Foundation post-doctoral fellowship for basic scientists (PF-PDF-1898) and a clinical research award (PF-CRA-2073). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewers disclosure

Peer reviewers on this manuscript have no relevant financial relationships or otherwise to disclose.

Additional information

Funding

Institutional funding only.