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Chang-Hao Yang, Long-Sheng Fan, Frank Yang; Implantation of a high-density, flexible CMOS imaging sensor retinal prosthesis in minipig eyes. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5099.
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A flexible 4,096-pixel retinal chip was fabricated consisting of an integrated 180 nm CMOS circuits with 30 μm-pitched image sensors and micro electrode array that capable of forming biphasic current distribution of images. In the present study, we developed a technique to implant this retinal prosthesis into the subretinal space of minipig eyes and test their biocompatibility.
An ab externo and transscleral approach for the implantation of retinal prosthesis was applied. Six Orchid island minipigs was used. After cutting open the conjunctiva, a partial thickness 3 × 2.5 mm scleral flap was dissected 6 mm posterior to the limbus in the superior temporal quadrant. A partial core vitrectomy to remove the vitreous and enable the raising of a retinal bleb was performed. The choroid was cauterized and penetrated with diathermy. The tip of a 30-gauge cannula was passed under the retina to create a bleb and a small amount of viscoelastic substance was injected into the bleb. The retinal prosthesis was inserted through the scleral flap into the subretinal space under the bleb. The scleral flap was closed when the array was in place and the final location of the prosthesis was visually confirmed by indirect ophthalmoscope. The sclerotomies and the conjunctiva was closed. The position of the prosthesis was evaluated with optical coherence tomography (OCT) in vivo after surgery. The animals were sacrificed 3 and 6 month postoperatively. Morphological changes of the retinas was investigated by H&E staining. Tunnel and immunohistochemical staining further evaluated apoptosis and changes in neural cells in the retinas.
The high-density, flexible CMOS imaging sensor retinal prosthesis was implanted into 6 minipig eyes. OCT examinations showed that the retinal chip was in good approximation with retina. H&E staining showed no inflammatory reaction around the retinal chip. Tunnel staining and immunohistochemical staining for glial fibrillary acidic protein and opsin demonstrated no apoptosis or changes in Muller cells, photoreceptors, or other neural cells in the retinas.
An ab externo and transscleral approach was successfully developed for implantation a high-density, flexible CMOS imaging sensor retinal prosthesis into minipig eyes. The retinal chip was biocompatible with retina tissues. The retinal prosthesis might have a strong potential for clinical application.
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