Abstract
This study aims at substituting the essential functions of photoreceptors in patients who are blind owing to untreatable forms of hereditary retinal degenerations. A microelectronic neuroprosthetic device, powered via transdermal inductive transmission, carrying 1500 independent microphotodiode-amplifier-electrode elements on a 9 mm2 chip, was subretinally implanted in nine blind patients. Light perception (8/9), light localization (7/9), motion detection (5/9, angular speed up to 35 deg s−1), grating acuity measurement (6/9, up to 3.3 cycles per degree) and visual acuity measurement with Landolt C-rings (2/9) up to Snellen visual acuity of 20/546 (corresponding to decimal 0.037 or corresponding to 1.43 logMAR (minimum angle of resolution)) were restored via the subretinal implant. Additionally, the identification, localization and discrimination of objects improved significantly (n = 8; p < 0.05 for each subtest) in repeated tests over a nine-month period. Three subjects were able to read letters spontaneously and one subject was able to read letters after training in an alternative-force choice test. Five subjects reported implant-mediated visual perceptions in daily life within a field of 15° of visual angle. Control tests were performed each time with the implant's power source switched off. These data show that subretinal implants can restore visual functions that are useful for daily life.
Highlights
Photoreceptors—cones and rods—in the outermost layer of the retina convert light into an electrical current that provides input to the second layer, i.e. the bipolar cell neurons
This study aims at substituting the essential functions of photoreceptors in patients who are blind owing to untreatable forms of hereditary retinal degenerations
Control tests were performed each time with the implant’s power source switched off. These data show that subretinal implants can restore visual functions that are useful for daily life
Summary
Photoreceptors—cones and rods—in the outermost layer of the retina convert light into an electrical current that provides input to the second layer, i.e. the bipolar cell neurons (figure 1a,b). These signals are processed within the retinal neuronal network and are forwarded via the ganglion cell axons that form the optic nerve to the lateral geniculate nucleus and to the visual cortex. The remaining visual pathway, from the bipolar cells onwards, remains largely functional. Various groups have attempted to replace photoreceptive function using technical devices to restore visual sensation in these patients. Approaches of stacking photodiodes in series to use, similar to solar cells, the light of an image itself for neuronal stimulation have been shown to be
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