Biomedical implant for vision prothesis

Yes, a surgical procedure is used to implant Argus II. The surgery can typically be completed within 4 hours and requires general anaesthesia. A one-night hospital stay may be required. Pre- and post-operative medication will be defined as necessary by the physician. Support from family or friends is recommended but not required for the post-operative follow-up.

As with any surgical procedure or implanted device, there are risks. Please refer to the safety information or consult your physician directly.

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Following implantation surgery, patients return to the clinic several times over the next few months for medical follow-up, to have their system custom programmed, and to receive training on how to use the system. Once this fitting and training is completed, the patients may begin to use the device at home. At this point, patients may elect to receive rehabilitation sessions conducted by a low-vision therapist. These sessions are intended to teach patients how to interpret and use their new visual input to develop skills in their daily lives.

For more information about the system: Argus II For any other questions, please consult your physician directly or send a message to Second Sight: Patients Email Address. The effectiveness of this device for this use has not been demonstrated. The retinal implant provides stimulation to induce visual perception in blind individuals. Argus II is currently approved and intended for use in patients with severe to profound retinitis pigmentosa RP who meet the following criteria: Adults, age 25 years or older Bare light or no light perception in both eyes. If the patient has no residual light perception, then evidence of intact inner layer retina function must be confirmed.

Advances in retinal prosthesis systems

Previous history of useful form vision. Aphakic or pseudophakic. But different scientists' methods for achieving this vary. What's more, bionic eye technology is still in its infancy compared with cochlear implants for hearing loss. Several bionic eye implants are in development, but currently only one is available in the United States, and it is suitable only for blindness caused by specific eye diseases.

However, as research continues, more and more people may soon benefit from high-tech bionic eyes. A bionic eye is not the same thing as a prosthetic eye.

Visual prosthesis

Prosthetic eyes also called "glass eyes" or "artificial eyes" replace the physical structure and appearance of an eye that must be removed due to trauma, pain, disfigurement or disease. Bionic eye implants, on the other hand, work inside the existing eye structures or in the brain. They are designed to achieve functional vision goals — as opposed to physical, cosmetic ones. The Argus II Retinal Prosthesis System consists of a tiny eyeglasses-mounted camera and a transmitter that wirelessly sends signals to an electrode array that is implanted onto the damaged retina of a blind person.

Who Can Benefit From Currently Available Bionic Eyes?

Just as there is no single cause for blindness, there's likewise no one cure. To determine whether a bionic eye could help you see, it's important to know the reason s for your vision loss. The process of sight begins when light enters the eye. The cornea and lens focus light onto the retina at the back of the eyeball.

Epiretinal placement i.


Subretinal placement i. Suprachoroidal placement i. Aside from implant location, the other issue of greater interest is the level of visual resolution that retinal prostheses can deliver. There is marked convergence in the retinal periphery where hundreds of rods feed into one peripheral bipolar cell, while in the central macular region fovea , the ratio of cones to retinal ganglion cells approaches Achieving this ratio is unlikely with a retinal device because as the individual microelectrode diameter becomes smaller, the charge density per unit area increases exponentially 32 for the same supra-threshold stimulating current, thereby increasing the risk of tissue damage.

The visual resolution achievable with the current generation of retinal prostheses is discussed within the section for each device below. Individual cone photoreceptors can be seen as discrete dots.

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Within this mosaic macular region, the ratio of photoreceptors to retinal ganglion cells approaches , allowing maximal visual resolution. Activation of one microelectrode would therefore result in equivalent simultaneous activation of hundreds of photoreceptors. The resolution achievable with this current generation of retinal implant is thus limited.

As well as directly applying electrical charges to initiate action potentials, three other methods are in development. The optogenetic approach aims to replace the lost photoreceptors by turning the remaining inner retinal cells e. Natural ambient light which has a variation of 15 log units in intensity 26 does not have the intensity to activate the retina reliably.

Wang et al. This has the potential of overcoming the limitation of microelectrode size and charge density with microelectrodes.

It also offers the flexibility to process visual images with advanced encoding algorithms, before converting images into NIR pulses for subsequent MPDA stimulation. The third method of inner retinal stimulation, still at experimental stage, is the use of ultrasound waves to stimulate the retinal ganglion cells. Naor et al. These two portions are connected via a cable that traverses the sclera. It has also been shown that the device can be safely removed without any serious adverse effect. During the trial, one patient's device had to be explanted due to recurrent erosions and one patient developed retinal detachment which was successfully repaired.

Two patients developed endophthalmitis but all were treated successfully with intra-vitreal antibiotics and the patients retained good functional use of their device. All the three patients were implanted early on in the trial and with amendment to the implantation protocol, none of the subsequent patients developed endophthalmitis. Twenty-eight patients underwent functional assessments and all reported reliable perception of phosphenes. Orientation and mobility functions were tested by following a white line on a dark floor, and locating a dark door on a white wall from the centre of a room.

Patients performed significantly better with the device switched on compared with the device switched off. More recently, da Cruz et al. Four subjects were able to consistently read unrehearsed short words of up to four letters.

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The first generation of Retinal Implant AG devices were originally implanted in 11 subjects in as part of an acute clinical trial Clinical Trials. The implant was placed subretinally and powered externally by a percutaneous wire, which exited in the retro-auricular region of the subject as a connection plug. Although visual function improvement was demonstrated, the implant was removed from all the subjects after a few weeks as per protocol except in one subject who declined removal and no long-term durability data are available from the acute trial.

Structurally, the alpha-IMS is also made up of an internal part and an external part. The internal part see Fig. The MPDA is a light-sensitive 3. Each pixel is composed of one photodiode, which feeds into one microelectrode via an amplifier. The wirings within the MPDA converge to form a foil, which exits the eye ball at its equator. The inset shows a photograph of an external coil held in place by magnetic attraction to the subdermal internal coil. Within each MPDA, there are photosensitive pixel-generating elements; each photodiode is further connected to an independent titanium nitride microelectrode via an amplifier.

The MPDA is designed to be inserted subretinally to allow reception of the visual images focused on to the retina by the front of the eye. Image conversion is achieved by light intensity-dependent generation of photocurrent by each photodiode, which is then amplified logarithmically before feeding into the associated microelectrode to stimulate the immediate retinal neurones. Electrical energy is generated by internal coil induction with an external coil, and subsequently used to amplify the MPDA-electrode system response.

Preliminary results on the performance of the first generation implant have been reported on three patients. One subject in particular was able to recognize geometric shapes and read large letters to formulate simple words. A possible explanation for his superior visual performance is that his MPDA is implanted sub-foveally, whereas the other two subjects' are located extra-foveally. Stingl et al. Two adverse events were reported: one patient developed post-operative subretinal bleed with secondary intra-ocular pressure rise to 46 mmHg, which settled on medical treatment.

The other patient suffered intra-operative optic nerve damage when the tip of the implant touched the optic nerve, resulting in no perception of light NPL vision post-operatively. Despite the adverse events, the visual outcomes have been favourable: three patients were able to recognize individual letters spontaneously when presented under high contrast conditions, with the best visual acuity reported to be logMAR 1. In , a electrode system was implanted into four patients in an acute clinical trial and they were able to discern simple lines and spots, as well as detect horizontal movements.

The main difference between Epi-Ret 3 and other video glasses devices is that the internal coil and ASIC hermetic case are packaged into a compact disc form similar in dimension to that of an intra-ocular lens and inserted into the capsular bag.