PURPOSE  To observe long-term efficacy and reliability of a kind of microelectrode array implanted into the optic nerve sheath of rabbit eyes.
METHODS  Fifty-six eyes of 56 rabbits were studied. Eight rabbits were used to testify spatial discrimination of a 9-channel microelectrode array inserted beneath the dura mater of optic nerve to contact the pia mater. Eight rabbits served as the normal control group. Long-term efficacy and reliability were observed in the other 40 rabbits. The observation period was up to one year. Electrically evoked potentials (EEPs) were used to certify the efficacy of the microelectrode array, and the current thresholds were recorded. Visual evoked potentials (VEPs) and different pathological examinations were used to examine possible damage of the optic nerves.
RESULTS  Spatial discrimination of about 20^o was confirmed by EEP maps. EEPs could be recorded up to six months after implantation. Two weeks after the surgery, the current thresholds increased due to fibrous encapsulation. Pathological changes were not noticed one year after implantations.
CONCLUSIONS  Implantation of microelectrode array beneath the dura mater of optic nerve could be an ideal approach for optic nerve prosthesis, and is proved safe after one year observation. To maintain the efficacy of the microelectrode array, more researches are needed to resolve the problem of fibrous encapsulation, which may result in elevation of current thresholds.