The value of preoperative tests in the selection of blind patients for a permanent microelectronic implant.

PURPOSE To determine the best candidates (ie, those requiring lowest current levels delivered to the retina to elicit visual perceptions) for long-term implantation of a microelectronic retinal implant through a series of preoperative visual, psychophysical, and electrophysiological tests. METHODS This study protocol was granted an investigational device exemption by the Food and Drug Administration and was approved by the institutional review board at the University of Southern California. After informed consent was obtained, all subjects underwent the following preoperative tests: dark-adapted bright flash and 30-Hz flicker electroretinograms, electrical evoked responses (EERs) using a Burian-Allen corneal electrode to stimulate the globe, and psychophysical tests to evaluate the light and electrically elicited visual perceptions. Intraocular stimulation (IOS) of the retina was performed by an array of electrodes positioned on the internal limiting lamina. RESULTS Lower vision correlated with less sensitive psychophysical responses (P<.0001). Lower vision and less sensitive psychophysical tests correlated with higher EER values for stimulus pulse widths of 2 ms (P<.0008) and 4 ms (P<.0002). Lower IOS currents correlated with more sensitive psychophysical responses (P<.02) and lower EER values at 4 ms (P<.04). CONCLUSIONS Preoperative testing, especially psychophysical and electrophysiological tests to assess light and electrically driven visual responses, can help in evaluating patients for suitability for receiving a permanent microelectronic retinal implant. Further study is warranted.

[1]  M. Humayun,et al.  MORPHOMETRIC ANALYSIS OF THE MACULA IN EYES WITH DISCIFORM AGE-RELATED MACULAR DEGENERATION , 2002, Retina.

[2]  A. M. Potts,et al.  The electrically evoked response of the visual system (EER). , 1968, Investigative Ophthalmology.

[3]  Gholam A. Peyman,et al.  Safety, Feasibility and Efficacy of Subretinal Artificial Silicon RetinaTM Prosthesis for the Treatment of Patients with Retinitis Pigmentosa , 2002 .

[4]  Neal S Peachey,et al.  Subretinal implantation of semiconductor-based photodiodes: durability of novel implant designs. , 2002, Journal of rehabilitation research and development.

[5]  J. Mortimer,et al.  Visual sensations produced by optic nerve stimulation using an implanted self-sizing spiral cuff electrode , 1998, Brain Research.

[6]  A. Milam,et al.  Preservation of the inner retina in retinitis pigmentosa. A morphometric analysis. , 1997, Archives of ophthalmology.

[7]  J. Weiland,et al.  Pattern electrical stimulation of the human retina , 1999, Vision Research.

[8]  W. H. Dobelle.  Artificial vision for the blind by connecting a television camera to the visual cortex. , 2000, ASAIO journal.

[9]  R. H. Propst,et al.  Visual perception elicited by electrical stimulation of retina in blind humans. , 1996, Archives of ophthalmology.

[10]  A. Milam,et al.  Morphometric analysis of the extramacular retina from postmortem eyes with retinitis pigmentosa. , 1999, Investigative ophthalmology & visual science.

[11]  R A Normann,et al.  The Utah intracortical Electrode Array: a recording structure for potential brain-computer interfaces. , 1997, Electroencephalography and clinical neurophysiology.

[12]  J. L. Stone,et al.  Morphometric analysis of macular photoreceptors and ganglion cells in retinas with retinitis pigmentosa. , 1992, Archives of ophthalmology.

[13]  R D Ross,et al.  Is perception of light useful to the blind patient? , 1998, Archives of ophthalmology.

[14]  Malini Narayanan Nadig.  Development of a silicon retinal implant: cortical evoked potentials following focal stimulation of the rabbit retina with light and electricity , 1999, Clinical Neurophysiology.

[15]  A. M. Potts,et al.  The electrically evoked response (EER) of the visual system. II. Effect of adaptation and retinitis pigmentosa. , 1969, Investigative ophthalmology.

[16]  Manjunatha Mahadevappa,et al.  Visual Perception in Blind Subjects with Microelectronic Retinal Prosthesis , 2003 .

[17]  A. M. Potts,et al.  The electrically evoked response of the visual system (EER). 3. Further contribution to the origin of the EER. , 1970, Investigative ophthalmology.