silicon and Retinitis-Pigmentosa

To determine the safety and efficacy of the artificial silicon retina (ASR) microchip implanted in the subretinal space to treat vision loss from retinitis pigmentosa.. The ASR microchip is a 2-mm-diameter silicon-based device that contains approximately 5000 microelectrode-tipped microphotodiodes and is powered by incident light. The right eyes of 6 patients with retinitis pigmentosa were implanted with the ASR microchip while the left eyes served as controls. Safety and visual function information was collected.. During follow-up that ranged from 6 to 18 months, all ASRs functioned electrically. No patient showed signs of implant rejection, infection, inflammation, erosion, neovascularization, retinal detachment, or migration. Visual function improvements occurred in all patients and included unexpected improvements in retinal areas distant from the implant.. Subjective improvements included improved perception of brightness, contrast, color, movement, shape, resolution, and visual field size.. No significant safety-related adverse effects were observed. The observation of retinal visual improvement in areas far from the implant site suggests a possible generalized neurotrophic-type rescue effect on the damaged retina caused by the presence of the ASR. A larger clinical trial is indicated to further evaluate the safety and efficacy of a subretinally implanted ASR.

Topics: Aged; Blindness; Electric Stimulation; Electrodes, Implanted; Electroretinography; Evoked Potentials, Visual; Fluorescein Angiography; Follow-Up Studies; Humans; Male; Middle Aged; Pilot Projects; Prosthesis Implantation; Retina; Retinitis Pigmentosa; Safety; Semiconductors; Silicon; Visual Acuity; Visual Fields; Visual Perception

Topics: Female; Follow-Up Studies; Humans; Middle Aged; Prosthesis Implantation; Retinitis Pigmentosa; Semiconductors; Silicon; Time Factors; Visual Prosthesis

In a published pilot study, a light-activated microphotodiode-array chip, the artificial silicon retina (ASR), was implanted subretinally in 6 retinitis pigmentosa (RP) patients for up to 18 months. The ASR electrically induced retinal neurotrophic rescue of visual acuity, contrast, and color perception and raised several questions: (1) Would neurotrophic effects develop and persist in additionally implanted RP patients? (2) Could vision in these patients be reliably assessed? (3) Would the ASR be tolerated and function for extended periods?. Four additional RP patients were implanted and observed along with the 6 pilot patients. Of the 10 patients, 6 had vision levels that allowed for more standardized testing and were followed up for 7+ years utilizing ETDRS charts and a 4-alternative forced choice (AFC) Chow grating acuity test (CGAT). A 10-AFC Chow color test (CCT) extended the range of color vision testing. Histologic examination of the eyes of one patient, who died of an unrelated event, was performed.. The ASR was well tolerated, and improvement and/or slowing of vision loss occurred in all 6 patients. CGAT extended low vision acuity testing by logMAR 0.6. CCT expanded the range of color vision testing and correlated well with PV-16 (r = 0.77). An ASR recovered from a patient 5 years after implantation showed minor disruption and excellent electrical function.. ASR-implanted RP patients experienced prolonged neurotrophic rescue of vision. CGAT and CCT extended the range of acuity and color vision testing in low vision patients. ASR implantation may improve and prolong vision in RP patients.

Topics: Artificial Organs; Color Vision; Equipment Design; Feasibility Studies; Follow-Up Studies; Humans; Pilot Projects; Retina; Retinitis Pigmentosa; Silicon; Time Factors; Treatment Outcome; Vision Tests; Vision, Low; Vision, Ocular; Visual Acuity

Topics: Animals; Darkness; Electrodes, Implanted; Electroretinography; Neuroprotective Agents; Photoreceptor Cells, Vertebrate; Prostheses and Implants; Rats; Retina; Retinitis Pigmentosa; Silicon; Time Factors

Current retinal prosthetics are designed to stimulate existing neural circuits in diseased retinas to create a visual signal. However, implantation of retinal prosthetics may create a neurotrophic environment that also leads to improvements in visual function. Possible sources of increased neuroprotective effects on the retina may arise from electrical activity generated by the prosthetic, mechanical injury due to surgical implantation, and/or presence of a chronic foreign body. This study evaluates these three neuroprotective sources by implanting Royal College of Surgeons (RCS) rats, a model of retinitis pigmentosa, with a subretinal implant at an early stage of photoreceptor degeneration. Treatment groups included rats implanted with active and inactive devices, as well as sham-operated. These groups were compared to unoperated controls. Evaluation of retinal function throughout an 18 week post-implantation period demonstrated transient functional improvements in eyes implanted with an inactive device at 6, 12 and 14 weeks post-implantation. However, the number of photoreceptors located directly over or around the implant or sham incision was significantly increased in eyes implanted with an active or inactive device or sham-operated. These results indicate that in the RCS rat localized neuroprotection of photoreceptors from mechanical injury or a chronic foreign body may provide similar results to subretinal electrical stimulation at the current output evaluated here.

Topics: Animals; Electric Stimulation; Foreign-Body Reaction; Neuronal Plasticity; Photoreceptor Cells, Vertebrate; Prostheses and Implants; Rats; Recovery of Function; Retinitis Pigmentosa; Silicon