Purpose:
This work is related to the efforts of the Boston Retinal Implant Project to develop a sub-retinal prosthesis to restore vision to the blind. The specific purpose of this presentation is to develop a safe surgical method to implant a relatively large electrode array sub-retinally.
Methods:
The eyes of 19 Yucatan mini pigs were studied, 4 of which underwent survival surgeries and 15 had acute surgeries. Inactive, micro systems PI-2611 polyimide arrays that were 16 µm thick with 100 Iridium Oxide electrodes 200 µm in diameter were used in survival surgeries. The array is 5 mm in diameter, which could theoretically provide vision over >15° of visual angle. To avoid excessive bleeding during surgery, systemic hypotension was maintained. 2 ab externo methods were used: (1) choroidectomy without retinal detachment and (2) choroidotomy with induced retinal detachment. A scleral flap was dissected posterior to the limbus temporally followed by vitrectomy. In method 1, scleral fibers were shaved away, a choroidectomy was made, the array was placed on the retina and the flap was sutured. In method 2, a local retinal detachment was made underneath the flap. Scleral fibers were shaved away and a choroidotomy was made. The array was inserted using a guide.
Results:
Of 14 acute surgeries with choroidectomy, 5 resulted in successful implantation of an array (See 2005 ARVO abstract). Of 2 survival surgeries with choroidectomy, 1 resulted in the retina bulging out which only allowed for insertion half way into the sub-retinal space and 1 surgery failed because of retinal tear. 1 acute surgery and 1 chronic surgery with choroidotomy were successful. In 1 survival surgery with choroidotomy, the pig died.
Conclusions:
Large arrays can be sub-retinally implanted. The method utilizing a choroidotomy with induced retinal detachment facilitated implantation of our relatively large electrode array. More experiments will be performed to gain further experience with this procedure.
Keywords: retina • choroid • vitreoretinal surgery