Candidates for visual prosthetic implants find the procedure most successful if the optic nerve was developed prior to the onset of blindness.
[5] Argus II, co-developed at the University of Southern California (USC) Eye Institute[6] and manufactured by Second Sight Medical Products Inc., was the first device to have received marketing approval (CE Mark in Europe in 2011).
Most other efforts remain investigational; the Retina Implant AG's Alpha IMS won a CE Mark July 2013 and is a significant improvement in resolution.
In the spring of 2011, based on the results of the clinical study which were published in 2012,[15] Argus II was approved for commercial use in Europe, and Second Sight launched the product later that same year.
[18][19][20] This type of device is implanted in the eye's posterior chamber and works by increasing (by about three times) the size of the image projected onto the retina in order to overcome a centrally located scotoma or blind spot.
[19][20] Created by VisionCare Ophthalmic Technologies in conjunction with the CentraSight Treatment Program in 2011, the telescope is about the size of a pea and is implanted behind the iris of one eye.
[22] A Southern German team led by the University Eye Hospital in Tübingen, was formed in 1995 by Eberhart Zrenner to develop a subretinal prosthesis.
The chip is located behind the retina and utilizes microphotodiode arrays (MPDA) which collect incident light and transform it into electrical current stimulating the retinal ganglion cells.
[citation needed] The first UK implantations took place in March 2012 and were led by Robert MacLaren at the University of Oxford and Tim Jackson at King's College Hospital in London.
[28] On 19 March 2019 Retina Implant AG discontinued business activities quoting innovation-hostile climate of Europe's rigid regulatory systems and unsatisfactory results in patients.
[29][30] Joseph Rizzo and John Wyatt at the Massachusetts Eye and Ear Infirmary and MIT began researching the feasibility of a retinal prosthesis in 1989, and performed a number of proof-of-concept epiretinal stimulation trials on blind volunteers between 1998 and 2000.
[31] The brothers Alan and Vincent Chow developed a microchip in 2002 containing 3500 photodiodes, which detect light and convert it into electrical impulses, which stimulate healthy retinal ganglion cells.
[32] Daniel Palanker and his group at Stanford University developed a photovoltaic retinal prosthesis in 2012,[33] that includes a subretinal photodiode array and an infrared image projection system mounted on video goggles.
These images are projected onto the retina via natural eye optics, and photodiodes in the subretinal implant convert light into pulsed bi-phasic electric current in each pixel.
Following this proof of concept, Palanker group is focusing now on developing pixels smaller than 50μm using 3-D electrodes and utilizing the effect of retinal migration into voids in the subretinal implant.
The members of the consortium consisted of Bionics Institute, UNSW Sydney, Data 61 CSRIO, Center for Eye Research Australia (CERA), and The University of Melbourne.
The device aimed to provide functional central vision to assist with tasks such as face recognition and reading large print.
Each prototype consisted of a camera, attached to a pair of glasses which sent the signal to the implanted microchip, where it was converted into electrical impulses to stimulate the remaining healthy neurons in the retina.
Arrays of activated iridium oxide film (AIROF)-coated electrodes will be implanted in the visual cortex, located on the occipital lobe of the brain.
[citation needed] Stephen Macknik and Susana Martinez-Conde at SUNY Downstate Medical Center are also developing an intracortical visual prosthetic, called OBServe.