Abstract
Abstract: :
Purpose:To investigate the effects of chronic electrical stimulation of the normal canine retina with an implanted epiretinal stimulating array. Methods:An implantable retinal stimulator was implanted in five dogs. The electronics were packaged in a hermetic ceramic case approximately 25x25x5 mm. This case was fixed to the skull using standard plastic surgery materials and the skin was closed over the implant. A multiconductor wire extended from the stimulator case terminating in a 4x4 electrode stimulating array. The wire was tunneled subcutaneously to the orbit. The wire was wrapped around the eye and was sutured at multiple points to the sclera. After a complete vitrectomy, the stimulating array was inserted into the orbit via a sclerotomy. The array was secured to the retina with a single retinal tack. After a 2-4 week recovery period, an electronic test system was worn by the dog to wirelessly provide the power and data to the implanted device. A preprogrammed stimulus pattern was applied to the retina. The implant was monitored with indirect ophthalmscopy, fluorscein angiography, and electroretinography. Results:Electrical stimulation was performed in 5 dogs for periods of 11-60 days. Stimulation was performed for 10-12 hours/day. Electrical stimulation at current densities of 0.1 mC/cm2 and 0.05 mC/cm2 did not cause noticeable damage to the retina. In some cases, pressure on the retina from improper orientation of the stimulating array resulted in localized retinal atrophy and hyperpigmentation of the RPE. This occurred mainly at the edges of the electrode array. The implantation and stimulation did not significantly affect the electroretinogram compared to the unoperated control eye. The retina under the array remained well perfused. Conclusion:Electrical stimulation of the retina with up to 0.1 mC/cm2 stimulating pulses did not cause noticeable damage the retina. In some instances, mechanical interaction between the retina and the stimulating array resulted in retinal folds or discoloration of the RPE mainly at the periphery of the stimulating array.
Keywords: 554 retina • 568 retinitis • 308 age-related macular degeneration