The picture is taken from the article "Subretinal electronic chips allow blind patients to read letters and combine them to words", E. Zrenner et al.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.
The picture is taken from the article "Subretinal electronic chips allow blind patients to read letters and combine them to words", E. Zrenner et al.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.
Post a Comment