Comprehensive Visual and Mobility Training Using Computer-Assisted Rehabilitation Environment (CAREN) After Argus Retinal Prosthesis Surgery
Phase: NA
Conditions: Retinitis Pigmentosa
Sponsor: The Cleveland Clinic

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Title: Comprehensive Visual and Mobility Training after Retinal Prosthesis Surgery 
Principle Investigators: Aleksandra Rachitskaya, MD (Cole Eye Institute), Alex Yuan, MD, PhD (Cole Eye 
Institute), & Jay L. Alberts, PhD (Biomedical Engineering) 
Version Date: October, 2017 
 
BACKGROUND 
As of 2010, the estimated number of visually impaired people in the world is 285 million with 39 million 
considered legally blind and 246 million having low vision.1 Blindness and visual impairment are 
associated with higher medical care expenditures, a greater number of informal care days, and a 
decrease in health utility.2 In 2006, the annual total financial burden of major adult visual disorders in 
the United States was estimated to be $35.4 billion ($16.2 billion in direct medical costs, $11.1 billion in 
other direct costs, and $8 billion in productivity losses).3 
The advances within the field of ophthalmology have led to novel interventions for patients with 
profound vision loss who previously had no treatment options. In addition to gene and stem cell 
therapies, there is a burgeoning field of artificial vision due to such devices as retinal and cortical 
implants. Presently, the resolution of artificial vision is termed “ultra-low vision” as it allows for crude 
perceptions of larger, high contrast objects.4 Despite rapid development of these new technologies, they 
lack objective and standardized methods of assessing visual function in this patient population.  
Retinitis pigmentosa (RP) is a group of hereditary retinal degenerative diseases demonstrating 
significant genotypic and phenotypic heterogeneity. Typically, patients with RP are born with normal 
vision; however, rod photoreceptor cell death leads to symptoms of nyctalopia and visual field loss.  
Over time, the disease progresses affecting the cone photoreceptor cells and patients have diminished 
color vision and central vision loss. In severe cases the disease renders patients completely blind – 
unable to detect light. There is currently a dearth of treatment options for these patients, but retinal 
prosthesis and other potential therapies such as stem cell therapy, gene therapy, and cortical prostheses 
are in development across Europe and North America. However, the methods of assessment and 
integration for optimal use have not been developed and represents a major obstacle in the use and 
development of these technologies. 
The aim of the current project is to fill the 
unmet clinical needs around the objective 
assessment of visual function and develop an 
outcome-oriented visual rehabilitation approach 
using the computer assisted rehabilitation 
environment (CAREN) system. The development of 
objective outcomes coupled with a rehabilitation 
protocol will provide a unique clinical-technical 
platform that will: 1) facilitate Staff within Cole Eye 
Institute to better compete for NIH funding, 2) 
result in a scalable outcome assessments conducive 
to commercialization and 3) create an industry 
standard in assessment of the ultra-low vision 
patient. The technology and rehabilitation approach 
will be developed using a unique group of ultra-low 
vision patients with a diagnosis of RP who 
underwent Argus II retinal prosthesis implantation.   
Argus II retinal prosthesis system: A novel device to 
restore vision: The Argus II Retinal Prosthesis System 
Figure 1: The Argus II Retinal Prosthesis System. (A) 
Implanted components. The retinal tack secures the 
electrode array to the surface of the retina. The implant 
coil and electronics case are secured around the sclera 
with the scleral band. (B) Glasses worn by the patient 
contains a camera and an external coil which 
communicate wirelessly with the implant coil. (C) The VPU 
is worn by the patient and is connected to the glasses. 

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(Argus) is the only FDA-approved treatment for patients blind from RP (Second Sight Medical Products; 
Sylmar, CA). The Cleveland Clinic Argus team, Drs. Aleksandra Rachitskaya and Alex Yuan, within the 
Cole Eye Institute have performed the greatest number of surgeries post-FDA market approval in the 
United States and the institute is considered to be an Argus center of excellence by the manufacturer. 
Between June 2015 and May 2017, a total of 10 implant surgeries have been performed at Cleveland 
Clinic out of a total of approximately 80 in the U.S. The Argus system was named the 2014 Cleveland 
Clinic No. 1 Medical Innovation of the Year. In 2015 the work of the Cleveland Clinic Argus Team was 
recognized as one of the top Clinical Achievements of the Year.  Considering the importance, relevance, 
innovation and commercial and consumer visibility of the Argus system, developing outcomes and a 
protocol for evaluation of this cutting edge technology will yield multiple scientific publications and 
commercial attention which will facilitate success of extramural and industry sponsored research. 
The Argus system consists of a retinal implant that is surgically implanted into one eye, a pair of 
glasses with an integrated video camera, and a video processing unit (VPU) (Figure 1). These 
components work together to provide electrical stimulation to the electrode array, stimulating the 
patient’s remaining inner retinal cells. The electrode array 
consists of 60 platinum electrodes arranged in a 6 x 10 grid 
pattern centered over the macula (Figure 2), the part of the 
retina responsible for central vision. The primary sensory 
neurons are the photoreceptors which reside in the outer 
retina.  Normally, these cells are responsible for 
phototransduction and synapse with second order bipolar 
cells in the inner nuclear layer. The bipolar cells then 
synapse with the third order neurons, the ganglion cells, 
which relay visual input to the brain. In RP, there is a drastic 
reduction in photoreceptor outer segments and abnormal 
residual rods and cones. The inner retinal neurons, although 
reduced in number, appear to be preserved.5,6 The 
preservation of ganglion cell function is important for the 
function of the Argus, as the second and third order neurons 
are stimulated by the Argus electrode array.  
The Argus system works by capturing video through the camera mounted on the glasses worn 
by the patient. The image is captured as the patient slowly moves his/her head and “scans” the scene. 
The video is sent to the VPU which encodes brightness via stimulus amplitude and sends the stimulus 
pattern wirelessly to the implanted device via the implant coil. Stimulation of the electrode array results 
in the generation of visual percepts or phosphenes (flashes of light or a glow) detected by the patient in 
a retinotopic manner.7 Patients who receive the Argus do not have their vision restored. Rather, the 
device provides them with a new type of artificial vision. 
Given that phosphene interpretation is not intuitive, in order for this vision to become 
meaningful, patients must undergo a post-implantation rehabilitation regimen. The training focuses on 
learning how to use the device, develop the necessary scanning skills to know how to “scan the scene”, 
and how to interpret the new artificial vision. Currently, there is a fundamental knowledge gap in how to 
best approach visual rehabilitation of Argus recipients. Patient success with the Argus is largely 
dependent on the rehabilitation process; however, there are no established guidelines for rehabilitation.  
Patients who receive the system currently work with low vision therapists and orientation and mobility 
(O&M) specialists with the goal of increasing safety, mobility, and independence. The number of 
sessions and the type of training varies from one patient to the next. In addition, the field is lacking 
standardized outcomes to measure visual functional recovery. Currently, the only objective tests utilized 
include visual function tests (square localization, direction of motion, and grating visual acuity) 
Figure 2: The Argus electrode array is 
shown centered over the macula next to 
the optic nerve. 

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developed by the Argus manufacturer. All the tests are performed with the patient seated in front of a 
touch screen monitor and the patient responds to images and their direction/orientation on the screen. 
The current visual function tests are limited as they lack the ability to mimic “real world” situations and 
thus fail to address if the device is useful to a patient. Moreover, in our experience, they do not always 
correspond with each patient’s functional outcomes, device usage, and overall satisfaction with the 
device.  
 
Optimizing utilization of low vision innovations requires a multi-disciplinary approach: Sensorimotor 
integration is key during postural control activities. The central nervous system integrates three major 
systems to maintain posture and balance: visual, vestibular, and somatosensory.8 Of those three 
systems, vision is the main sensory system used to maintain standing posture.9 With vision impairment, 
individuals experience impaired bilateral coordination,10 increased postural sway during static standing11 
and increased sway during sit-to-stand transfers.12 The visual, vestibular, and somatosensory systems 
are heavily dependent on one another.8 Just as the onset of visual impairment results in higher fall risk,13 
it is possible that regaining visual function will alter postural control and heighten fall risk.   
Given these unique limitations to visual rehabilitation in the Argus population, a collaboration 
between Drs. Rachitskaya and Yuan and Dr. Alberts’ was born to investigate more effective approaches 
to the evaluation and rehabilitation process. Dr. Alberts’ laboratory contains one of the only non-
military Computer Assisted Rehabilitation Environment (CAREN) system. The CAREN is a versatile, multi-
sensory virtual reality system with a fully integrated Vicon three dimensional (3D) motion capture 
system, a dual belt instrumented treadmill with a six degree of freedom motion base platform, and a 
180° curved projection screen with surround sound audio to immerse an individual into a virtual 
environment (Figure 3).14,15 A harness is donned during ambulation and balance activities to ensure 
patient safety. The programmable software of the CAREN system allows for the creation and 
modification of a variety of interactive modules. Modules can be as simple as reaching for an objects on 
a blank screen, and as complex as crossing the street during rush hour, and can be adjusted to increase 
contrast and complexity as patient’s abilities improve. The functionality of CAREN is unlike that of any 
other rehabilitation assistive tool and is only available at a few facilities in the United States. Collectively, 
the Cleveland Clinic is uniquely positioned to attract extramural and industry sponsored research, as we 
are already an established clinical partner for many technology companies. No other center in the 
United States has the combined clinical, 
engineering, and commercialization 
expertise. The proposed project utilizing 
Argus recipients will serve as a model of 
study that will be extended to other 
industry partners and future clinical trials 
and studies.    
CAREN would allow Argus 
recipients to be trained in a safe, 
controlled, and standardized 
environment. Additionally, 
biomechanical outcomes (gait variables, 
center of mass and positional sway 
during balance activities, head position 
to capture scanning techniques) can be 
collected during training to measure 
patient performance. The addition of 
biomechanical outcomes resulting in 
Figure 3: CAREN system. The 180-degree projection screen allows 
an individual to be immersed in an activity or scene while 
performing balance or gait activities on the platform. 

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objective measures of gait, posture, and visual awareness will provide a more complete picture of 
functional performance. 
Recognizing the need and opportunity to develop affordable and objective methods of assessing 
balance and gait, the Alberts’ lab developed a way to use the accelerometer and gyroscope of the iPad 
to provide biomechanical measures of postural sway during static standing and gait. Biomechanical 
measurements from the iPad have been validated against traditional biomechanical measures including 
3-D motion capture16 and force platforms,17 and are able to differentiate between a healthy and 
diseased population.18 The biomechanical measures from the iPad will be used to supplement clinical 
assessments. The inclusion of biomechanically-based methods to augment clinical evaluations is a novel 
application of technology that will lead to a more complete understanding of the functional 
rehabilitation of the ultra-low vision patient population. 
 
SPECIFIC AIMS 
The goal of the current project is to fill the unmet clinical needs around the objective assessment of 
visual function and develop outcome-oriented visual rehabilitation approach using the computer 
assisted rehabilitation environment (CAREN) system for Argus recipients. 
Aim 1:  Determine feasibility of clinical and biomechanical outcome measures on individuals with 
ultra-low vision. To date, there are no valid and reliable functional outcome measures for individuals 
with ultra-low vision. This study will determine the feasibility of functional and biomechanical outcome 
measures that have been established as valid and reliable in fully sighted individuals on Argus recipients. 
Aim 2:  Develop a comprehensive vision rehabilitation program for Argus recipients using the CAREN 
system. The team will consist of ophthalmologists/surgeons, Argus patient coordinator, visual function 
testing administrator, biomedical engineers, physical therapists and rehabilitation specialists. The 
collaborative team is well-trained to create a comprehensive rehabilitation program with a focus on 
functional outcomes. The program will focus on contrast sensitivity training, object identification, visual 
scanning, and object tracking. Body proprioception in relation to other objects will be a key focus of the 
rehabilitation, as safety with mobility is paramount. Ultimately an eight session rehabilitation program 
(2x/week for 4 weeks) will be created.   
 Aim 3: Determine the effects of a 4-week visual retraining session on Argus recipients. The 8 session 
rehabilitation program (2x/week for 4 weeks) will be implemented in a total of 5 patients implanted 
with the Argus II device. The patients will be tested at baseline and after the eight session protocol. The 
primary outcome will be change in the Timed Up and Go and an object navigation course. Standard 
visual outcomes as well as biomechanical outcomes will also be used. 
 
APPROACH 
Table 1 displays a timeline of the 
study design. Approval will be 
obtained from the Institutional 
Review Board of the Cleveland 
Clinic. The multidisciplinary team 
will collaborate on rehabilitation 
protocol development and quality 
assurance of the CAREN technology 
in Quarter 1. This will take several 
months due to the high level of 
collaboration that must occur by 
the engineers, vision experts, and rehabilitation experts. The visual capabilities status post Argus 
placement can vary widely, thus tasks must be able to be used on all subjects.   
Table 1: Proposed study timeline 
  
Year 1 
  
Q1 
Q2 
Q3 
Q4 
Institutional Review Board Approval 
 
 
 
 
Programming of CAREN modules 
  
  
  
  
Quality assurance of CAREN modules 
  
  
  
  
Subject enrollment 
  
  
  
  
Data analysis 
  
  
  
  
Manuscript preparation 
  
  
  
  

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Recruitment and Outcomes Testing: 
Once CAREN programing and quality assurance is complete, subjects will be enrolled in Quarters 2-3 to 
complete the training modules. Subjects will be recruited from the database of patients who have had 
the Argus device implanted at the Cleveland Clinic Cole Eye Institute. Subjects will be enrolled in this 
study for a minimum of 6 weeks, as visualized in Figure 4. Study enrollment will begin at the time of 
informed consent and study participation will end after completion of the EOT day 2 visit.  
Inclusion criteria are as follows: 1) implanted Argus device, 2) ability to provide informed consent, 3) 
ability to follow two-step commands, 4) ability to ambulate 300+ feet with or without visual assistance, 
and 5) able to tolerate Argus device turned on for >20 continuous minutes.   
Participants will be excluded from participation if they have: 1) dementia, 2) musculoskeletal 
contraindication to exercise or walking, or 3) cardiopulmonary contraindication exercise (i.e. 
uncontrolled heart failure, cardiac arrhythmia, or pulmonary disease). 
Outcomes will be assessed at baseline and end of treatment (EOT), as visualized in Figure 4. 
Table 2 describes the outcomes that will be collected: visual function, overground, and CAREN 
outcomes.  Three visual function tests (VFT) will be assessed: square localization, direction of motion 
and grating visual acuity.  The square localization test presents a 2.75” square (250 pixels) at a random 
location on a black background and the subject is instructed to touch the 
square.  The direction of motion test assesses the patient’s ability to 
determine the direction an object is moving by presenting a white line 
(1.4’’ wide) that moves across the screen in a random series of directions 
and angles.  The grating visual acuity test measures the patient’s visual 
acuity using the principles of acuity charts modified for ultra-low vision 
subjects. The subject is presented with black and white bars in one of four 
orientations (horizontal, vertical, diagonal to the left or diagonal to the 
right), and the subject provides a verbal response as to which orientation 
they perceived the bars. 
To determine functionality, the participant will also complete 
overground testing.  The Timed Up and Go (TUG) test is a test of mobility 
where the individual is required to stand, ambulate 3 meters, turn, and 
return to a seated position in the chair.19 During the TUG the iPad is 
attached to the patient’s waist and the accelerometer and gyroscope 
collect biomechanical data that allows for analysis of the transfer, 
ambulation, and turning.   The Five Time Sit to Stand requires the subject 
to stand up and sit down from a standard height chair without the use of 
their upper extremities.20  This will be tested with the Argus device on and 
off to see the effects of vision on transfer ability.  Postural sway will be 
measured during static standing by volumetric sway using the iPad. This 
test will be performed with the Argus device on and off. The Activities-
specific Balance Confidence (ABC) scale has been used in individuals with 
visual impairments to measure confidence with household and 
community mobility.13 Participants will complete an object navigation 
course modeled after Nau, et al.21 The object navigation course simulates 
obstacles that are commonplace in a community setting: ramp, curb, and stepping over and around 
objects. Time to completion of the obstacle course will be recorded.  The CAREN system will be used for 
baseline and EOT testing to track spatiotemporal gait parameters and visual tracking.   
 
Because of the anticipated length of time and cognitive demand required to complete all 
outcomes testing, both baseline and EOT testing will occur over a two days during the first and last 
weeks of study participation. Day one will include standard visual outcomes, ABC Scale administration, 
Figure 4: Overview of 
baseline assessment (week 
1), intervention (weeks 2-
5), and end of treatment 
(EOT) assessment protocol 
(week 6). 

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and iPad assessments in the Cole Eye Center. Day two will include the CAREN testing and the object 
navigation course in the Mellen Center.  
 
 
 
Intervention: Following baseline testing, participants will begin a 2x/week training program using the 
CAREN system. Training will continue for at least four weeks, or until completion of eight sessions. 
Interventions will be collaboratively designed between an expert in CAREN system operations and a 
physical therapist or physical therapist assistant. Because each recipient of the Argus implant has unique 
challenges and needs, treatment sessions will be tailored on an individual basis, with the over-arching 
goal of improving functional vision and safety. Participants will engage in static and dynamic activities to 
simulate the demands of real-life situations, and will be permitted seated or standing rest breaks as 
needed.  It is relevant to note that the testing module will be completely different from the training 
module to minimize the training effect.   
 
Feasibility of CAREN system in a single Argus recipient: Preliminary testing of the CAREN system on a 
single Argus recipient was performed. The patient was able to get on the treadmill and interface with 
the CAREN system. The patient was able to identify simpler targets on the screen as well as successfully 
identify large letters (3 out of 3), while scenes with lower contrast or with increased visual stimuli were 
more challenging. The patient tolerated testing for over 2 hours. This preliminary session indicates that 
Argus recipients are able to interface with and perform tasks on the CAREN system and can provide our 
team with biomechanical data. 
 
Data Confidentiality: Study data that will be collected on the CAREN system will be de-identified using 
only the participant's study number.  For purposes of the 3-D motion analysis, participants are 
Table 2: Outcome measures  
 
Name of outcome measure 
Domain tested 
Testing Day 
Standard Visual Outcomes 
 
Square localization, direction of 
motion and grating visual acuity   
Ultra-low visual function tests currently used as an 
outcomes measure for Argus recipients 
1 
Overground Outcomes 
 
Timed Up and Go 
Transfer, gait, turning 
1 
Five Time Sit to Stand (Argus on, 
off) 
Transfers 
1 
Postural sway measured by iPad 
(Argus on, off) 
Static standing balance 
1 
Activities-specific Balance 
Confidence (ABC) Scale 
Balance confidence questionnaire  about household and 
community tasks  
1 
Object Navigation Course 
Real-world object navigation consisting of stepping over and 
around objects, curb and ramp negotiation 
2 
CAREN Outcomes 
 
Baseline visual assessment 
Shapes displayed from large to small to establish baseline 
visual function 
2 
Contrast sensitivity 
Lightening black background by 10% until subject no longer 
able to identify the shape 
2 
Accuracy of object localization  
Object displayed on CAREN screen; time, biomechanical 
coordinates of turning head to locate objects  
2 
Spatiotemporal gait parameters 
Gait variables (i.e. velocity, cadence, step length, etc.) 
during single and dual task conditions x 2 minutes 
2 

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videotaped; however this video will not leave the computer of the CAREN system without further 
written consent from the participant.  The Apple iPad will be used to collect some of the cognitive and 
biomechanical data necessary for this study.  Only a study number will be associated with this iPad 
data.  All data which is captured on the iPad will be securely transmitted to a HIPPA compliant research 
database.  All points of access to the research database will take place over Transport Layer 
Security/Secure Sockets Layer encrypted connections.   
Other outcome measures will be collected on Redcap ®, a secure electronic database that limits access 
to study personnel.  Other electronic data will be labeled with only the subject number.  The original 
signed and dated informed consent document along with any paper that may be used for data collection 
will be maintained in a study binder in a locked office within Cole Eye Institute.  The regulatory binder 
for this study will be kept in Cole Eye, and only research personnel will have access to this information. 
 
Potential Risks: There are potential risks and discomforts to this study.  There is a risk of muscle soreness 
and fatigue that comes along with exercising.  There is a risk of cognitive and visual fatigue from the 
tasks as well.  Participants will be permitted to rest as needed.  There is a risk of falls in the clinical and 
VR setting, although in the VR setting participants will wear a harness to prevent falls.  With the markers 
that will be worn for the gait analysis, there is a risk of temporary skin irritation.  Although the intensity 
of exercise will be low, there is a risk of a cardiovascular event.  All exercise personnel will be CPR 
certified and there is a medical emergency team located on site.  There may be other risks with this 
intervention that are not yet known.   
 
Data Collection and Statistical Analysis: The 10-camera Vicon system in combination with D-Flow 
software captures the 3D position of several retro-reflective markers placed on anatomic landmarks of 
the body.  Gait recordings will focus on the lower extremities, while object localization will require 
markers placed on the glasses worn by the patient. Recordings are completed at 100 Hz and filtered 
using a 2nd order low-pass Butterworth filter with a 6 Hz cut-off frequency. Data output from the CAREN 
system will be analyzed using custom Matlab scripts.  Spatiotemporal parameters of velocity, step 
length, step width, and stride time will be calculated from the averaged per gait cycle.  This study has a 
case-series design and statistically will be treated as such.  Thus the study team will be looking for 
minimal clinical importance difference and trends from pre to post testing in the biomechanical and 
clinical outcomes. 
 
 

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