This document summarizes the history and current state of bionic eyes or retinal prosthetics. It discusses how various types of prosthetics have evolved from early models that stimulated the visual cortex to current retinal implants. The retinal implants can be either epiretinal or subretinal, with the Argus II being the first approved epiretinal implant. The document outlines how retinal implants work, the implantation procedure, the vision outcomes patients experience, rehabilitation methods, and challenges that still remain including improving resolution. Bionic eyes have progressed from an idea to trials demonstrating they can restore some useful vision to the blind.

1. BIONIC EYE
A RAY OF HOPE
Presenter: Dr. Anahita Shroff
Moderator: Dr. Yeshwanth Kumar

2. INTRODUCTION
• Vision loss can be caused by a
range of factor, inherited,
acquired or age related
• Bionic eye is a novel device
which helps restore a part of
perception in the visually
impaired
• Currently, it is applicable for
Retinitis Pigmentosa and Age
Related Macular
Degeneration(ARMD) patients

3. CONCEPT
• Visual prostheses, in theory, can be used for any conditions causing
blindness by damaging the visual pathway at any point
• However, current research mainly focuses on retinal degenerative
blindness caused by diseases like RP and ARMD
• RP or ARMD mainly cause Retinal Photoreceptor layer damage
• A significant part of Inner Retinal layers are spared

4. PURPOSE
• The main aim of the current viable
Bionic eye models is to utilize these
functional inner retinal layers and
stimulate them, thereby generating an
impulse that travels through the optic
nerve and eventually reaches the cortex

5. HISTORY
• PHOSPHENES: Phenomenon of seeing light without light
entering the eye
• The most common phosphenes, are pressure phosphenes,
caused by rubbing or applying pressure on or near the closed
eyes (Greeks)
• One example of a pressure phosphene is demonstrated by
gently pressing the side of one's eye and observing a colored
ring of light on the opposite side (Newton)

6. TYPES OF PROSTHESES - The Evolution
• INTRA-CORTICAL
• OPTIC NERVE
• RETINAL
• EPIRETINAL
• SUBRETINAL
• RECENT ALTERNATIVE
APPROACHES

7. INTRA-CORTICAL PROSTHESIS
• Bypasses all diseased visual pathway
neurons rostral to the primary visual cortex
• Histological changes induced
• Complex cortical organization therefore
poor reproducibility
• Morbidity and mortality due to surgical
complications
• Foerster, a German neurosurgeon, in 1929 demonstrated that electrical
stimulation of the visual cortex could lead to the perception of phosphene.
The first prototype of a device was conceived by Brindley in 1960s who
improvised a device on the cerebral cortex
• Current models of the intracortical prosthesis include the Utah electrode
array and the Illinois Intracortical Visual Prosthesis project.

8. OPTIC NERVE PROSTHESIS
• Entire visual field is represented in a small area
which can be reached surgically and presents a
viable anatomic location for an implant
• Dural dissection increases risk of infections and
blood flow interruption to optic nerve
• Processing power of the bipolar, amacrine and
horizontal cells is lost, hence much more image
processing must be achieved by the implant rather
than relying on intact human physiologic pathways
• Central macular fibres far from peripheral cuff
• Veraart et al, attempted this method by employing the concept of a spiral nerve
cuff electrode. It is surgically implanted circumferentially on the external surface
of the optic nerve. Since the device does not penetrate the optic nerve sheath, it
relies on the Principle Of Retinotopic Organisation within the optic nerve.
Recently, penetrating intraneural optic nerve prosthesis are under research.

9. RETINAL PROSTHESIS - TYPES
• EPIRETINAL: Device is implanted into the
vitreous cavity and attached to the inner retinal
surface, so the electrical stimulation meets the
inner retina first.
• SUBRETINAL: Device is implanted in the
potential space between the retinal pigment
epithelium and the neurosensory retina, so the
electrical stimulation meets the outer retina first
• Three retinal bionic eyes have been approved
for commercial sale: the Argus II (Epiretinal)
developed in the USA, the Alpha-AMS
(Subretinal) in Germany, and the Intelligent
Retinal Implant System (IRIS V2)- the only
epiretinal with 150 electrodes – in France

10. RETINAL PROSTHESIS - COMPONENTS
ARGUS II:
EXTERNAL:
1. Video camera
2. Video processing unit(VPU)
3. Coil (Transmit data
wirelessly via
radiofrequency telemetry)
INTERNAL:
1. Coil ( Receives data )
2. Internal Processing
unit(ASIC- Application
specific integrated circuit)
3. Electrode array

11. RETINAL PROSTHESIS - WORKING

12. RETINAL PROSTHESIS - IMPLANTATION
• A 360-degree peritomy is performed and the hermetic casing is sutured onto the scleral surface in the
superotemporal quadrant.
• The antenna coil is placed under the lateral rectus muscle and sutured to the sclera in the
inferotemporal quadrant.
• The rest of the device’s silicone band is placed under the remaining rectus muscles and joined
together in the superonasal quadrant with a Watzke sleeve.
• A standard 3-port pars plana vitrectomy is used to implant the intraocular components of the Argus®
II .
• The posterior hyaloid face and any existing epiretinal membranes are removed to optimize contact
between the micro-electrodes and the retinal neurons.
• 5.2 millimeter wide sclerotomy is made in the superotemporal quadrant, at a distance of
approximately 3 mm posterior to the limbus.
• The micro-electrode array is inserted through the sclerotomy and place in the macular region.
• Once positioned optimally, the micro-electrode array is secured by a spring-tensioned titanium retinal
tack inserted at the heel of the array.
• The sclerotomy is then sutured close. Tutoplast pericardial is placed in the superior temporal quadrant
over the hermetic casing. The Tenon’s capsule and conjunctiva is closed.

15. RETINAL PROSTHESES- COMPARISON
EPIRETINAL
• Vitreous acts as a sink for heat dissipation from the
microelectronic device
• Minimal number of microelectronics are
incorporated into the implantable portion of the
device
• Wearable portion of electronics allows for easy
upgrades without requiring subsequent surgery
• Electronics allow the user and the doctor full
control over every electrode parameter and digital
signal processing in imaging objects, allowing the
implant to be customised for each patient
• Requirement of technology to provide prolonged
adhesion of the device to the inner retina
• Increased current requirement due to greater
distance of the target bipolar cells from epiretinal
device than with the subretinal device
SUBRETINAL
• Closer proximity to the next surviving neurons to
the visual pathway (i.e. bipolar cell)
• Therefore less current requirement
• Lack of a mechanical means of fixation
• Limited subretinal space to place electronics
• Close proximity of the retina to the electronics
which would increase the risk of thermal injury to
the neurons

16. RECENT ALTERNATIVE APPROACHES
• Suprachoroidal transretinal stimulation (STS)
• Placing a stimulating electrode in the
suprachoroidal space or in the fenestrated sclera
along with a ground electrode in the vitreous
cavity may allow for a less invasive method of
achieving functional percepts.
• Advantages to this approach are that the surgery
is less complicated, the electrodes are less
invasive to the retina, and can be removed or
replaced easily if damaged

17. RECENT ALTERNATIVE APPROACHES
• Microfluidic Retinal Prosthesis Implant project
• This visual prosthesis will mimic normal chemical signaling between the retina and
brain
• Digital images may be transposed into neurochemical signals through an implanted
microfluidic chip that provides continuous meaningful information to the retina and
brain
• Artificial Synapse Chip project
• Created a design for a flexible retinal interface which aims to improve visual resolution
of an electronic retinal prosthesis by addressing cells individually and mimicking the
physiological stimulation achieved in synaptic transmission

18. VISION WITH BIONIC EYE

19. VISION WITH BIONIC EYE
• Depends on number and density of electrodes
• Phosphene perception and localization
• Recognition and discrimination of forms
• Localization of targets
• Motion detection and navigation
• Rarely, recognize alphabets

20. VISION WITH BIONIC EYE- REHABILITATION
• Rehabilitation plays a very important role in the vision of patients who
have undergone a bionic eye implant
• Rehabilitation kits are used, with various shapes on a contrasting
background that can be felt as well as visually explored, along with several
hand-eye coordination and scanning tasks
• Experienced occupational therapists, orientation and mobility instructors,
and certified low-vision therapists comprise the team of professionals that
are involved in optimizing the visual outcome post implantation
• Implants like Argus II have various modes like inverse video, filters for glare
and low-contrast conditions, etc… , with appropriate guidance this helps in
improving their skills for orientation, object localization, and identification.
• The therapist must be experienced and creative enough to optimize the
training for each patient as per their needs

21. VISION WITH BIONIC EYE- MEASUREMENT
• Standard visual function tests, are not capable of measuring prosthetic vision aka ULV(Ultra Low
Vision)
• Functional Low-Vision Observer Rated Assessment (FLORA), is an assessment that tracks how subjects
perform in vision-related activities of daily living in the home enviroment and in a computer-based
visual function test with the device on and off.
• The strengths of FLORA are the assessment of the user in the home environment, the combination of
subjective (user and rater) and objective (task performance) factors, and the evaluation by 2
independent experts. The weakness is that the measures are not standardized because all activities
involve familiar surroundings and objects in users’ homes
• Calibrated performance measures and self-reported outcomes through standardized questionnaires
are much more likely to gain acceptance as standards by regulatory bodies, than FLORA.,
• A targeted visual functioning questionnaire for individuals with ULV recently was developed,
(Dagnelie G, et al; Invest Ophthalmol Vis Sci 2014;55:ARVO Eabstract 2150) and Argus II users have
measurable outcomes on this self-report instrument and on a set of standardized activities
• These instruments currently are being validated (not approved yet) in a larger population of ULV
patients and retinal implant users and can be expected to play a role in future clinical trials of retinal
prostheses and other novel sight-restoring treatments

22. CHALLENGES AND LIMITATIONS
• Minimum number, type and location of the viable inner retinal cells required for a
useful prosthesis are currently not known
• Biocompatibility of any retinal prosthesis is an issue due to the potential
chemical, biophysical, and immunological reactions to the implanted materials
and the surgical procedure
• Potential effects of heat generation and transfer of electrical energy have not
been investigated fully
• Most outcome measures remain subjective and only a few groups have identified
parameters to test subjects objectively
• Only through these objective measures can the results be reproducible

23. CONCLUSION
• The number of blind patients is constantly increasing and 10% of them have no light
perception from various causes
• The field of visual prostheses has started from a mere dream to early patient trialS
• It is only with the continued research efforts of the many teams from all over the world that
these blind people may have a chance to see again

24. REFERENCES
• Visual Prosthesis : Artificial Vision Brig A Banarji* , Col VS Gurunadh+, Col S
Patyal# , Col TS Ahluwalia**, Maj Gen DP Vats, SM, VSM++, Col M
Bhadauria (Retd)##
• A Quarter Century of Retinal Prosthesis Research and Development Mark S.
Humayun, MD, PhD,1 Eugene de Juan, Jr., MD,2 Gislin Dagnelie, PhD3
• EYEWIKI: Retina Prosthesis : Alladdin Makawi, B.S, Vinay A. Shah M.D.,
Peter Hao Tang, M.D., Ph.D., Leo A. Kim, MD, PhD, Dr John Davis Akkara
(MBBS, MS, FAEH, FMRF), Sandra R. Montezuma, MD, Sandra R.
Montezuma, MD