Table 2 Epiretinal device characteristics
Device | Electrode specifications | Implant Size | Benefits | Reported SAE/AE’s | Clinical Status |
|---|---|---|---|---|---|
NR600 | 600 3D microelectrodes (typical length of 150 ± 30 µm, and a maximum exposed tip height of 50 µm) | Three different lengths available varying between 20 and 26 mm in axial lengths | - Porous and chemically stable electrode material - Passivation layer to minimize shunting currents and limit electrode active area stimulation - Configurable settings - Lower peak intensity - No need for surplus wiring outside the eye - Relatively low risk procedure - Fast healing and recovery time | - Mild corneal edema along with slightly elevated intra-ocular pressure - Intra ocular lens luxation with subsequent elevated IOP | In clinical trials available in Italy, Israel, and Belgium |
IMIE 256 | 256 electrodes: two sizes of disc-shaped electrode diameters including 248 large electrodes (210 µm in diameter) and 8 smaller electrodes (160 µm in diameter) | 2 sizes: Area covers 4.75 mm × 6.50 mm center-to-center pitch is 350 µm for the large electrodes and 300 µm for the small electrodes | - Reduced risk of episcleral electronics capsule exposure - Greater density of functioning electrodes - 100% of subjects implanted performed better on visual tests with the system on versus off. - Compact size matching retinal curvature - Low power consumption - Reduced dissipated heat to surrounding tissue - Multiple layers of biocompatible and durable barrier material to withstand bodily fluid corrosion - Improved manufacturability for mass production allowing for future reduced costs [1 | - Device displaced slightly toward the upper temporal position in the macula - low intraocular pressure in the implanted eye 6 weeks after repositioning | Future clinical trials for testing in more patients over a longer follow-up period |
POLYRETINA | 2215 stimulating pixels (80 and 130 µm diameter) | 24 mm axially × 24 mm laterally × 14 mm wide | - Extra layer of PDMS substrate material to reduce strain - Foldable for implantation ease - Hemisphere shape matching retinal curvature - Reduced retinal tissue heating - Homogeneous temperature distribution during deposition - Large diameter of photovoltaic electrodes - Preserved high deformability - low level of acute immune response activation | Information not available | In vivo study showed that it restores light-evoked cortical responses at safe irradiance levels and is tolerable after two weeks if implantation |
EPI-RET3 | 25 electrodes (100 µm diameter) | 40 mm length × 3 mm width | - Wireless implant - Short surgical time - Direct electrode to retinal stimulation | - Four cases (three mild and one moderate) of non-progressive epiretinal gliosis at the tack fixation site - Inflammatory reaction in the implanted eye due to corneal sutures - Slight decline in residual visual perception in two patients post implant removal of the implanted eye - Minor choroidal atrophy within the area where the retinal tacks had been placed - removal of the implant had caused a retinal break (treated with laser coagulation and silicone oil tamponade) - acute sterile hypopyon after implantation - a thick epiretinal membrane in the tack area at the retinal center | Six patients were implanted for 28 days. No active clinical trials at this time |