Monday, 6 October 2014

The new method for the treatment of neurologically caused impairments of the visual system.

As it was announced on September 22, 2014,  The company EBS Technologies has opened its first ophthalmologic clinical site in Germany that is offering the use of the EBS NEXT WAVE™ brain stimulation device designed to expand the visual field of patients with impaired vision caused by glaucoma, stroke and other neurological diseases. 

On the official web-site of EBS Technologies you can find the detailed description of the therapy they propose: 

The EBS Therapy
The EBS Therapy (abbreviated Еlectrical Brain Synchronization) is a completely new method for the treatment of neurologically caused impairments of the visual system.

The EBS Therapy is a non-invasive, low risk electrical stimulation treatment device that is individually adapted to the patient’s condition in order to restore visual field losses caused by neurological disorders such as stroke, traumatic brain injury (TBI), anterior ischemic optic neuropathy (AION), Neuropathy of the optic nerve as well as several types of glaucoma. Common to all of these diseases is the damage of neuronal structures in the optic nerve and/or of those areas of the brain that are responsible for visual perception. Such damage may reduce the visual performance of the patient.

In some cases, the functionality of the optic nerve can be restored by a spontaneous reorganization of the brain (self-healing effect). However, most of these losses are considered to be permanent.

The EBS Therapy is made possible by the NEXT WAVE™ Technology, which uses patterns of current-driven electrical pulses that are applied via 4 electrodes around the patient’s eyes. 

Mechanism of Action 

According to information-theoretical approaches, the complete information of the brain is stored in the form of neurological networks. After an accident or because of specific neurological diseases of the brain (stroke or TBI as well as neuro-ophthalmological diseases such as glaucoma), these networks are damaged to varying degrees, which may result in a loss of function (e.g. visual field losses). This loss of function is not only caused by the death of affected cells, but also as a result of inactivity of the surviving cells in the network. 

One of the EBS Therapy mechanisms is to improve the residual function of these networks by reactivating the surviving but inactive cells and re-including them into the network (neuro-synchronization). In addition to this neuro-plastic effect, the alternating current stimulation of EBS Therapy also shows a neuro-protective effect as it influences the metabolism of the nerve cells. As a result, EBS Therapy restores parts of the brain functionality or reduces additional loss of function (e.g. glaucoma). 

EBS Therapy stimulates the retina of the patient (retino-fugal stimulation) and induces a series of action potentials that travel on the optic nerve back into the visual center of the brain. The brain interprets these signals as light sensations (phosphenes). At the same time, the measurement of brain-only EEG-signals allows for the optimization of pulse sequences in such a way that a sustainable improvement of the residual performance can be achieved (permanent learning effect).

The EBS Therapy consists of 10 sessions, which are held on 10 consecutive working days. One therapy session lasts up to 70 minutes. 

The efficacy of the EBS Therapy was demonstrated in a randomized, placebo-controlled, and double-blind trial.

Measurement criteria of this trial were changes in the visual field, which means the spatial perception of the optic nerve. These changes were defined and quantified by standardized perimetric measurements. With an average improvement of 24 % of the entire visual field, the trial data proved to be statistically significant.
The CE marked EBS Therapy is offered at qualified clinical centers in Germany.

Current experience shows that the treatment success of EBS Therapy can activate spontaneous processes of brain plasticity, which may lead to further improvement of the patient’s visual performances even after the completion of the therapy. 

Tuesday, 8 July 2014

Dr.’s Dobelle Cortical Visual Implant

I have found very exciting article of Dr. Dobelle “Artificial Vision for the Blind by Connecting a Television Camera to the Visual Cortex”. The article was published in 2000, so I would like to notice that many of the characteristics of the visual implant described below could be improved since that time. Personally I was impressed by the fact that the first cerebral implants aimed to stimulate the visual cortex were set up as early as in the 70s.

Dr. Dobelle along with more than 300 other scientists, physicians, engineers and surgeons have been developed cortical visual implant, which unlike some other artificial vision proposals (e.g. retinal stimulators) is applicable to virtually all causes of blindness. Particularly, the presence of the eyeballs is not necessary in this case.

The research group have also provided a battery powered, electronic interface which can replace the camera, permitting the sightless volunteer to directly watch television and use a computer, including access to the Internet.

The complete artificial vision system showing the computer and electronics package on the belt with output cable to the electrodes on the brain.

According to the author, the push for his research was made by a seminal paper published by Giles Brindley’s group in 1968. Their first human experiments in 1970-1972 involved cortical stimulation of 37 sighted volunteers who were undergoing surgery on their occipital lobe under local anesthesia to remove tumors and other lesions. In 1972-1973 they then stimulated the visual cortex of three blind volunteers who were temporarily implanted for a few days with electrode arrays.  
Their subsequent experiments have involved four blind volunteers implanted with permanent electrode arrays using percutaneous connecting pedestals. Two volunteers were implanted in 1974. One array was removed 3 months after surgery as planned, and the second one after 14 years. The second volunteer agreed to continue participation but his implant was removed due to a blood borne infection that did not originate with the implant.  The first five volunteers were operated on at the University of Western Ontario in London Canada. Two additional blind volunteers, including the subject of this article, were implanted in 1978 at the Columbia-Presbyterian Medical Center in New York City. They have both retained their implants for more than 20 years without infection or other problems.

 The Volunteer and Implant

Dr.Dobelle describes in details a 62 year old patient, who traumatically lost vision in one eye at age 22, and was totally blinded at age 36 by a second trauma. He was continually employed, before and after losing his sight, as an administrator by the State of New York. He retired in 1997 after 32 years of service. The electrode was implanted in 1978 when he was 41 years old. The implanted pedestal and intracranial electrode array were used to experimentally stimulate the visual cortex, on the mesial surface of the right occipital lobe, for more than 20 years.  However, the fifth generation external electronics package and software are entirely new, taking advantage of cutting edge technology that has only recently become available. An X-ray of the implanted visual cortex electrode array is shown in Figure below: 

X-ray of electrode array on the mesial surface of the right occipital lobe.

The original surgery in 1978 was performed under local anesthesia, and implants in future patients can probably be performed on an outpatient basis by most neurosurgeons.

Phosphenes and Their Map in The Visual Field

The Dr.’s Dobelle visual prosthesis produces black and white display of visual cortex “phosphenes” analogous to the images projected on the light bulb arrays of some sports stadium scoreboards.
When stimulated, each electrode produces 1-4 closely spaced phosphenes.
Each phosphene in a cluster ranges up to the diameter of a pencil at arms length. The Dr.’s Dobelle work team determined that the phosphene map occupies an area roughly 8 inches in height and 3 inches wide, at arms length.

 The Electronics Package

The 292 X 512 pixel charge coupled devices (CCD) black and white television camera is powered by a 9 V battery, and connects via a battery-powered National Television Standards Committee (NTSC) link to a sub-notebook computer in a belt pack. This f 14.5 camera, with a 69° field of view, uses a pinhole aperture, instead of a lens, to minimize size and weight. It also incorporates an electronic “iris” for automatic exposure control. The sub-notebook computer incorporates 233 MHz processor, 32 MB of RAM and a 4 GB hard disk. It also has an LCD screen and keyboard. The belt pack also contains a second microcontroller, and associated electronics to stimulate the brain. This stimulus generator is connected through a percutaneous pedestal to the electrodes implanted on the visual cortex. The computer and electronics package together are about the size of a dictionary and weigh approximately 10 pounds, including camera, cables, and rechargeable batteries. The battery pack for the computer will operate for approximately 3 hours and the battery pack for the other electronics will operate for approximately 6 hours. This general architecture, in which one computer interfaces with the camera and a second computer controls the stimulating electronics, has been used by Dr.’s Dobelle team in this, and four other substantially equivalent systems, since 1969. The software involves approximately 25,000 lines of code in addition to the sub-notebooks’ operating system. Most of the code is written in C++, while some is written in C. The second microcontroller is programmed in assembly language. 
To control costs and ensure easy maintenance, the commercial off-the-shelf (COTS) components are used. The computer, stimulating electronics, and software are all external, facilitating upgrades and repairs.

Performance of the System
Тhe Dr’s Dobelle system provides low parafoveal tunnel vision. The picture captured by the patient is black and white with  plus field defects (due to gaps between phosphenes; there is no depth perception.

The patient learnes to use the system within 1 one-day sessions, and he continues to practice 3-4 hours per day 2 or 3 days per week. With scanning the patient can routinely recognize a 6 inch square “tumbling E” (see pic. [а]) at five feet, as well as Snellen letters [b], HOTV test [c], Landolt rings [d], and Lea figures [e] of similar size. These psychophysical tests are summarized in Figure below: 

 The patient can also count fingers. With the exception of finger counting, these acuity tests have been conducted using pure black characters on a pure white background at an illumination greater than 1,000 lux. The volunteer can recognize a 2-inch high letter at 5 feet. This represents acuity of roughly 20/400.

Paradoxically, larger characters are slightly more difficult for this volunteer because they extend well beyond the limits of his visual “tunnel”. The rapid fall-off with characters smaller than 20/1200 is also quite reproducible.
Similar acuity results have been achieved with the television/computer/Internet interface replacing the camera, although scanning is slower.

Although stimulation of visual cortex in sighted patients frequently produces colored phosphenes, the phosphenes reported by this volunteer (and all previous blind volunteers to the best of their knowledge) are colorless. Probably, this is the result of post-deprivation deterioration of the cells and/or senaphtic connections required for color vision. Consequently, color vision may never be possible in this volunteer or in future patients. However, optical filters could help differentiate colors, and it is also conceivable that chromatic sensations could be produced if future patients are implanted shortly after being blinded, before atrophy of the neural network responsible for color vision.

Contrast is entirely a function of the software, with adjustment by the experimental team depending on the experimental situation. The system also allows “reversal” in which the world looks much like a black and white photographic negative. Reversal is particularly useful when presenting black characters on a white background. These characters are then reversed by the computer so they appear as a matrix of white phosphenes on the patient’s (otherwise dark) visual field. The phosphene map is not congruent with the center of the volunteer’s visual field. Phosphenes also move with eye movement. However, the volunteer’s ability to fixate with this artificial vision system is a function of aiming the camera using neck muscles, rather than eye muscles.

Edge Detection
Picture of the 38 inch high child mannequin, with a second ski cap placed at a random location on the wall. B, Same scene as above, after edge-detection using Sobel filters and black/white reversal. The blind volunteer is able to easily find the cap and detect the wall outlets. Similarly, doorways appear as an outline of white phosphenes on a black background. All processing can be performed and transmitted to the patient at 8 frames/second.

Ultrasonic Rangefinder

While using edge detection, it is particularly helpful for the blind patient to know how far the wall is located behind the mannequin.
By placing an electrostatic transducer on the left lens of the patient’s eyeglasses (lateral to the camera and below the laser pointer) Dobelle’s team has begun exploring the supplementary information that can be provided by modulating brightness, blink rate and identity of selected phosphenes.

One final comment is that none of the seven blind volunteers of  Dr’s Dobelle study have ever exhibited epileptic symptoms or other systemic problems related to the implant. Based on clinical experience during the last 30 years, implanting thousands of patients in more than 40 countries with other types of neurostimulators (to control breathing, pain, and the urogenital system), Dobelle’s team believes that the principal risk of their artificial vision device is infection, which might require removal of the implant in addition to antibiotic therapy.

Thursday, 8 May 2014

Biohybird retinal implant

Recently I found very interesting scientific article "Biohybrid Visual Prosthesis for Restoring Blindness" of Tohru Yagi.

Dr. Tohru Yagi's group has been conducting basic research and system design/integration on a biohybird retinal implant, which consists of cultured neurons on MEMS (Microelectromechanical Systems). Accordingly, “bio-hybrid" visual prosthesis combines the characteristics of regenerative medicine and visual prostheses. The first prototype consists of an external and an internal device. In operation, visual information is captured by a video camera in the external device. After encoding, this information is then sent to the internal device through an infrared (IR) communication unit. After the internal device receives the IR data, it generates appropriate electric pulses for stimulating the cultured neurons. Then cultured neurons send signals to the brain and the user can recognize visual information. In a biohybrid implant, it is the most prominent feature that the axons of transplanted neurons are used as living electric cables to form functional connections between neurons on the electrode array and the CNS.

The biohybrid implants require the implantation of not only the MEMS, but also the transplantation of nerve cells. Recently, it has been shown that when nerve cells and Schwann cells are together, irrespective of their origin, the visual cortex or periphery, the lengthening of nerve fibers is promoted by factors produced by Schwann cells, and myelin sheath formation occurs. Аn artificial optic nerve is prepared from Schwann cells (a semipermeable membrane tube filled with cultured Schwann cells, extracellular matrix, and neurotrophic factors), the axons of these nerve cells are guided to the higher visual cortex, connecting the MEMS with the visual cortex.

So, the nerve cells are used as a ‘living electrical cable". Once the connection is complete, it is considered that nerve cells transmit signals to the visual cortex in response to electrical pulses provided by the electrode array. Because nerve cells are transplanted as part of the process of fitting this visual prosthesis, a biohybrid implant is appropriate for blind patientswhose optic nerves and/or retinal ganglion cells are NOT intact such as glaucoma and diabetic retinopathy patients. Although biohybrid implants have advantages, there are many challenges related to nerve cell transplantation. Even if the axons of nerve cells can be guided to the visual cortex, unless a connection is formed between the neurons of the visual cortex and synapses, and a functional connection achieved via neurotransmitters, the signals cannot be communicated. 

The fundamental challenge for this prosthesis is the reliable reconstruction of signaltransmission function between an artificial device and transplanted nerve cells, and between transplanted nerve cells and the visual cortex.In addition, the long-term use of metallic electrodes induces connective tissues covering metal parts, and causes glioma aggregation and/or scar formation. Dr. Yagi's group regards it may be possible to develop a conductive polymer electrode that has a high affinity to biological tissues. This electrode may be bound to neural tissues at the molecular level so that a neuron will be stimulated intracellularly or quasi-intracellularly to decrease the threshold current significantly, and the functionality; biocompatibility of electrodes will be improved. For that purpose, they have been developing the technique of micro/nanofabrication of conductive polymers.

Tuesday, 25 March 2014

Subretinal prosthesis Alpha IMS

This post I would like to dedicate to the subretinal prosthesis Alpha IMS produced by Retina Implant AG, Reutlingen, Germany [company's web-site]. The scientific article of Prof. Eberhart Zrenner, one of the developers of subretinal prosthesis gives quite clear picture of what this prosthesis is [article's link]. 

Subretinal prothesis has the microchip which senses light and generates stimulation signals simultaneously at many pixel locations, using microphotodiode arrays. The Subretinal prothesis seeks to replace the function of degenerated photoreceptors directly by translating the light of the image falling onto the retina point by point into small currents that are proportional to the light stimulus. It is the only approach where the photodiode–amplifier–electrode set is contained within a single pixel of the MPDA such that each electrode provides an electrical stimulus to the remaining neurons nearby, thereby reflecting the visual signal that would normally be received via the corresponding, degenerated photoreceptor.

Figure 1. Subretinal implant. 

(a) The microphotodiode array (MPDA) is a light sensitive 3.0 x 3.1 mm CMOS-chip with 1500 pixel-generating elements on a 20 mkm thick polyimide foil carrying an additional test field with 16 electrodes for direct electrical stimulation (DS test field). 

(b) The foil exits approximately 25 mm away from the tip at the equator of the eyeball and is attached to the sclera by means of a small fixation pad looping through the orbit to a subcutaneous silicone cable that connects via a plug behind the ear to a power control unit. 

(c) Magnification of the DS electrode array showing the 16 quadruple electrodes and their dimensions. 

(d) Pattern stimulation via DS array (e.g. ‘U’). 

(e,f ) switching from a triangle to a square by shifting stimulation of a single electrode. 

(g) Magnification of four of the 1500 elements (‘pixels’), showing the rectangular photodiodes above each squared electrode and its contact hole that connects it to the amplifier circuit (overlaid sketch).
Essentially, an image is captured several times per second simultaneously by all photodiodes. Each element (‘pixel’) generates monophasic anodic voltage pulses at its electrode. Thus, pixelized repetitive stimulation is delivered simultaneously by all electrodes to adjacent groups of bipolar cells, the amount of current provided by each electrode being dependent on the brightness at each photodiode. Light is converted to charge pulses by each pixel. The chip is estimated to cover a visual angle of approximately 11º by 11º (1º approx. 288 mkm on the retina). The distance between two MPDA electrodes corresponds to a visual angle of 15 min of arc. Although small, it is sufficient for orientation and object localization, as is well established in patients with peripheral retinal dystrophies. Reading requires a field of 3 by 5 degrees.

Figure 2. Implant position in the body. 

(a) The cable from the implanted chip in the eye leads under the temporal muscle to the exit behind the ear, and connects with a wirelessly operated power control unit. 

(b) Position of the implant under the transparent retina. 

(c) MPDA photodiodes, amplifiers and electrodes in relation to retinal neurons and pigment epithelium. 

(d) Patient with wireless control unit attached to a neckband. 

(e) Route of the polyimide foil (red) and cable (green) in the orbit in a three-dimensional reconstruction 

of CT scans. 

(f) Photograph of the subretinal implant’s tip at the posterior eye pole through a patient’s pupil.
Because Alpha IMS microchip receives the image not from the external camera, but via eye, it is the only one retinal implant so far, where the image receiver array moves exactly with the eye. This has practical implications, as natural eye movements can be used to find and fixate a target.

In summer 2013 Alpha IMS received a CE Mark.

Price around 100,000 EUROs (as of April, 2013). 

Monday, 17 March 2014

BrainPort Device helps sightless to see by tongue

By Wicab, Inc. (Middleton, WI) it is being developed the device that by which blind people may "see" the outworld by the tongue.  

The unique technology was invented by Dr. Paul Bach-y-Rita in 1998 [analyticalarticle of Kenneth S. Suslick]. The technology allows transferring images from digital camera to the electrode array that sits upon tongue and stimulates its receptors.

More details about the device.
Visual system BrainPort developed by Wicab, Inc. [company'sweb] works in the following way: video comes from the camera attached to the forehead to the processor that controls zoom, brightness and other parameters of the image. Processor also converts the digital signals into electrical impulses and actually takes over the function of the retina.

Electrode array of 3x3 cm is comprised of more than 600 electrodes, each of which corresponds to several pixels in the camera. Light intensity directly affects the strength and duration of the current electrical signals which the tongue feels. Electrode array provides spatial orientation due to the flash in the center of the visual field is displayed in the form of a pulse in the middle of the array. White dots are transmitted by high electrical signal and black ones by the absence of voltage. Nerve endings dotting the tongue perceive these pulses. The volunteers have the feeling of champagne bubbles. It is still unclear where the data go further: to a visual or somatosensory cortex [material is taken from].

The device provides blind people by monochrome vision, the ability to see not just spots, but objects. Sightless have the possibility to make their usual actions: pour coffee, press the elevator button, read what is written on the wall.

About the development of the invention.
Dr. Paul Bach-y-Rita (1934-2006) started to conduct experiments with visual perception through tactile contact in the late 1960s. Initially he developed so-called tactile vision substitution systems capable to deliver visual information to the brain through the stimulants that are in contact with skin of one of several parts of the body (abdomen, back, thigh, fingertips). After sufficient trainings, blind people could feel the image in space rather than on the skin. Nevertheless, the success of the results was limited by inconvenience of practical application of the devices. Mechanical vibrotactile system were bulky and consumed a lot of energy, and  electrotactile systems required high voltages, especially in the areas of the fingertips due to the thick protective layer between the external environment and skin sensory receptors.

The tongue is very sensitive and mobile, and since it is in the protected area of the mouth, sensory receptors are close to the surface. Furthermore, saliva perfectly conducts electrical impulses. That is why Dr. Paul Bach-y-Rita conducted an experiment with tongue receptors [Scientist’s article] and demonstrated that tongue requires only 3% (5-15 V) of the voltage and much less current (0.4-2.0 mA), compared to the fingertips.

Watch the video from BBC:
Erik Weihenmayer: the blind rock climber who sees with his tongue

*All pictures are taken from the company-producer's website

Tuesday, 11 February 2014

OrCam: smart glasses

OrCam is a smart camera mounted on the frames of your eyeglasses, which “sees” text, recognizes objects and “whispers” in your ear. OrCam is a sensor that sees what is in front of you, understands what information you seek and provides it to you through a bone-conduction earpiece.
The device enables you to read books or newspapers, verify money note denominations, and even identify which product or item you are pointing at.

When you point to a specific article or paragraph, OrCam will start reading from the beginning of that section. Its powerful computer translates the printed word into audio in under two seconds.

At the moment the Price is $2,500.00

Sourse is

Sunday, 9 February 2014

Retinal Prosthesis Argus® II

 Image provided by Dr. Wentai Liu 
 What Argus® II is?

A retinal prosthesis is a biomedical implant intended to partially restore useful vision to people who have lost their sight 

due to a degenerative retinal disease such as retinitis pigmentosa (RP) that severely damages the photoreceptors in the eye. 

The sourse of picture

How does it work?

Argus II bypasses the damaged photoreceptors altogether. A miniature video camera housed in the patient’s glasses captures a scene. The video is sent to a small patient-worn  computer (i.e., the video processing unit – VPU) where it is processed and transformed into instructions that are sent back to the glasses via a cable. These instructions are transmitted wirelessly to an antenna in the implant. The signals are then sent to the electrode array, which emits small pulses of electricity. These pulses bypass the damaged photoreceptors and stimulate the retina’s remaining cells, which transmit the visual information along the optic nerve to the brain, creating the perception of patterns of light. Patients learn to interpret these visual patterns.

What kind of sight loss for?

Argus II currently provides some useful vision to patients with severe to profound vision loss due to outer retinal degeneration, such as retinitis pigmentosa (RP) .

What patient can see?

Argus II provides “somewhat pixelized” vision composed of spots of light which, in an ideal case, cover the central 20° visual field. This can be compared to a 30 cm ruler held out at arm’s length.
Some patients are able to easily discern forms, identify large written characters, and locate light sources, while others are not able to interpret spatial information about the visual scene with their system. In the study, patients were consistently better at performing orientation and mobility tasks using Argus II. 

As of March 2014 in commercial use and clinical trials, the Argus II system has been implanted into over 80 people (Fernandes RA et al). The best result achieved by the device was a visual acuity of 20/1260. Just to compare, the blindness is defined as greater than 20/500 by the World Health Organization.

Where is it approved?

Argus II is approved for use in the European Economic Area (CE Mark) in 2011. Since February 2013 also is approved in USA by FDA: statement