A group of blind subjects try out an experiment, about implant electrodes in a retina for detect movements. The subjects had an illness called retinitis pigmentosa. This genetic disease affects them so that their ability of sight decrease slow but progressively. The experiment, in principle, allow them to detect the direction of motion of a high-contrast moving bar on a flatscreen monitor, but not all of them could notice it. As result the half of blind subjects noticed the difference with their prosthesis. It proved that the blind subjects with the retina’s prosthesis could detect the movement that they couldn’t with their original vision.
A total of 28 blind subjects with retinitis pigmentosa were implanted with the Argus II prosthesis. The subjects had to pass an evaluation before the experiment: they had to have a visual acuity worse than 2.9 logMAR in both eyes, and have a bare light perception in at least one eye, ensuring that the optic nerve was functional.
The device, called Argus II system, is an epiretinal prosthesis that was fully implanted on and in the eye, with an external unit worn by the subject. The implant consist of a receiving and transmitting coil and electronics case fixed outside of the eye, and an electrode array, that is surgically positioned onto the surface of the retina and connect to the electronic case by a cable. The array is centered over the macula, a total of 60 electrodes were implanted, and they cover an area corresponding to 20º of visual angle.
The camera capture video and send the information to the processor, which convert the image to electronic signals and send them to the transmitter coil on the glasses. The episcleral implanted receive these data and send the signals to the electrode array, where electrical stimulation pulses are emitted. This stimulation localized cellular responses in the retina that travel through the optic nerve to the central visual system, resulting in visual percepts. They process the information in the following way: bright areas in the real-time video image create bright percepts and while dim areas correspond to a dim percept. Stimulation parameters used for the subjects were charge-balanced cathodic-first pulses with a pulse width of 0.46 milliseconds and the frequency was from 3Hz to 60Hz depending the subject.
They do a total of 80 sessions: at first, they listen to an audio message and a white bar extends across the screen at a randomly angle. In principle the speed of the bar was constant, but after, it varies depending the subject.
After each stimulus, the subjects draw the direction of motion they perceived on the touchscreen. After each response, an automated audio feedback was given, and the machine shows the results in the following way: if the response of the subject was within 15° of the stimulus angle in either direction, correct, or if not, it gives some general corrective feedback. Nevertheless, the subjects can’t correct their fails because the next stimulus is randomly chosen.
Moreover the sutdy is about 2 experiments: first, they compare the perfomance before using the glasses, and when they were wearing it; second, they only did it with the subjects that really manifested significatives differences, the 60 pixels were randomly chosen and while the field of view of the system remained identical to the normal condition, the spatial structure in the video image was eliminated.
As a result, 54% had a smaller mean error with the sytem on than when using their vision. Of the 15 subjects that really passed the prove, only 11 could do the second experiment, and 10 of them, had an smaller means error with the normal spatial mapping than with scrambled spatial mapping. We can see the results also in this graph:
Original article: I have already used the information from the original article, but if I have to emphasize something it would be that the language is a little bit complicated. Other thing very significant is that they explain everything fully of details.
The devices like that, can, in principle, improve our lifes, but only if a person who needs have the enough money, and with this like with the most of them, the price is incredibly high, and normal people can’t pay it. The bionic eye cost around $100,000 plus the surgey $15,000. So, are they really making our lifes easy? When a business company make something like this, new and very helpfull instrument, the price is huge, but on one hand the governments don’t help their manufacturing to make it cheaper, and on the other hand, the governments neither help normal people to pay it.
In conclusion, the new improvements in new instruments would be great if everyone could use it, because if they don’t it is not usefull at all. But this discoveries can also open doors to new discoveries, so it is not so bad. I hope that governments will become aware soon, and normal people can afford to live better.
ORIGINAL ARTICLE: JAMA Ophthalmology