Fitting a neural prosthesis using impedance and electrode height

• US 20070191911A1
• Filed: 12/01/2006
• Published: 08/16/2007
• Est. Priority Date: 12/01/2005
• Status: Active Grant

• Current Assignee: Doheny Eye Institute, Second Sight Medical Products, Inc.
• Original Assignee: Doheny Eye Institute
• Inventors: Greenberg, Robert, Humayun, Mark, Roy, Arup, Fine, Ione, Yadav, Sumit, Hines, Amy, Dai, Rongqing, McMahon, Matthew, Weiland, James, Horsager, Alan, Zhou, Dao
• Granted Patent: US 8,180,454 B2
• Time in Patent Office: Days
• US Class Current: 607/54
• CPC Class Codes: A61N 1/0543 Retinal electrodes
• CPC Class Codes: A61N 1/36046 of the eye
• CPC Class Codes: A61N 1/37247 User interfaces, e.g. input or presentation means

Abstract

The invention is a method of automatically adjusting an electrode array to the neural characteristics of an individual subject. The response to electrical neural stimulation varies from subject to subject. Measure of impedance may be used to predict the electrode height from the neural tissue and, thereby, predict the threshold of perception. Alternatively, electrode height may be measured directly to predict the threshold of perception. Also, impedance measurement may be used to quickly identify defective electrodes and proper electrode placement.

Claims

6. A neural stimulation system comprising:

a plurality of electrodes suitable to stimulate neural tissue;

means form measuring electrode height of at least one of said plurality of electrodes; and

means for estimating a threshold of perception based on said electrode height.

7. The neural stimulation system according to claim 6, further comprising

means for communicating said electrode height to a clinician.

8. The neural stimulation system according to claim 6, further comprising

means for measuring impedance between at least one electrode;

and

means for estimating a threshold of perception based on said impedance and said electrode height.

9. The neural stimulation system according to claim 8, further comprising

means for measuring retinal thickness;

and

means for estimating a threshold of perception based on said impedance, said electrode height and said retinal thickness.

10. The neural stimulation system according to claim 9, further comprising means for estimating a brightness response curve based on said impedance, said electrode height and said retinal thickness.

11. The neural stimulation system according to claim 6, wherein said means for measuring electrode height is OCT.

12. The neural stimulation system according to claim 6, wherein said means for measuring electrode height is ultrasound.

13. A neural stimulation system comprising:

a plurality of electrodes suitable to stimulate neural tissue;

means form measuring impedance of at least one of said plurality of electrodes;

means for communicating said impedance to an external device; and

means in said external device for displaying said impedance to a user.

14. The neural stimulation system according to claim 13, wherein said means in said external device for displaying said impedance to a user is a graphical representation of said plurality of electrodes.

15. The neural stimulation system according to claim 13, wherein said means in said external device for displaying said impedance to a user displays impedance by sound.

16. The neural stimulation system according to claim 13, wherein said means in said external device for displaying said impedance to a user displays impedance by color.

17. The neural stimulation system according to claim 13, wherein said means in said external device for displaying said impedance to a user displays impedance by graphical symbol.

18. A method of determining proper placement of a neural stimulation electrode array comprising:

placing an electrode array in proximity of neural tissue;

measuring impedance across the electrode array; and

determining, by the impedance, the proper placement of the electrode array.

19. The method according to claim 18, further comprising:

placing said electrode array in a plurality of locations;

measuring impedance across the electrode array in each location; and

determining, by the impedances, the best placement of the electrode array.

20. A method of fitting a neural stimulation device comprising:

providing a plurality of electrodes suitable to stimulate neural tissue;

measuring impedance of at least one of said plurality of electrodes; and

estimating a threshold of perception based on said impedance.

21. The method according to claim 20, further comprising communicating said impedance to a clinician.

22. The method according to claim 20, further comprising:

measuring electrode height; and

estimating a threshold of perception based on said impedance and said electrode height.

23. The method according to claim 22, further comprising

measuring retinal thickness;

and

estimating a threshold of perception based on said impedance, said electrode height and said retinal thickness.

24. The method according to claim 23, further comprising estimating a brightness response curve based on said impedance, said electrode height and said retinal thickness.

25. The method according to claim 20, further comprising estimating threshold of perception, based on said impedance for other geographically related electrodes.

26. A method of fitting a neural stimulation system comprising:

proving a plurality of electrodes suitable to stimulate neural tissue;

measuring electrode height of at least one of said plurality of electrodes; and

estimating a threshold of perception based on said electrode height.

27. The method according to claim 26, further comprising communicating said electrode height to a clinician.

28. The method according to claim 27, further comprising:

measuring impedance between at least one electrode; and

estimating a threshold of perception based on said impedance and said electrode height.

29. The method according to claim 28, further comprising:

measuring retinal thickness; and

estimating a threshold of perception based on said impedance, said electrode height and said retinal thickness.

30. The method according to claim 29, further comprising estimating a brightness response curve based on said impedance, said electrode height and said retinal thickness.

31. The method according to claim 26, wherein measuring electrode height is by OCT.

32. The method according to claim 26, wherein said measuring electrode height is by ultrasound.

33. A method of fitting and adjusting a neural stimulation device comprising:

providing a plurality of electrodes suitable to stimulate neural tissue;

measuring impedance of at least one of said plurality of electrodes;

communicating said impedance to an external device; and

displaying said impedance to a user.

34. The method according to claim 33, wherein displaying said impedance to a user is by graphical representation of said plurality of electrodes.

35. The method according to claim 33, wherein displaying said impedance to a user is a graphical representation of said plurality of electrodes.

36. The method according to claim 33, wherein displaying said impedance to a user is by color.

37. The method according to claim 33, wherein displaying said impedance to a user is by graphical symbol.

38. A method of determining a defective electrode in a neural stimulation device comprising:

providing a plurality of electrodes in proximity to neural tissue;

stimulating neural tissue with a biphasic pulse on said plurality of electrodes;

measuring voltage drops at a plurality of point during said biphasic pulse stimulation;

calculating a function of said voltage drops for said plurality of electrode;

comparing calculated results for said plurality of electrodes; and

determining that electrodes defective if its calculated results deviates significantly from the mean/median of all calculated results.

1. A neural stimulation system comprising:

a plurality of electrodes suitable to stimulate neural tissue;

means form measuring impedance of at least one of said plurality of electrodes; and

means for estimating a threshold of perception based on said impedance.

2. The neural stimulation system according to claim 1, further comprising

means for communicating said impedance to a clinician.

3. The neural stimulation system according to claim 1, further comprising

means for measuring electrode height;

and

means for estimating a threshold of perception based on said impedance and said electrode height.

4. The neural stimulation system according to claim 3, further comprising

means for measuring retinal thickness;

and

means for estimating a threshold of perception based on said impedance, said electrode height and said retinal thickness.

5. The neural stimulation system according to claim 4, further comprising means for estimating a brightness response curve based on said impedance, said electrode height and said retinal thickness.

39. The method according to claim 38, where said function is the voltage change between said points divided by current.

40. The method according to claim 38, wherein said function is a monotonicity function of the slope of said voltage drop measurements.

41. The method according to claim 38, wherein varies is varies by more than four standard deviations.

42. The method according to claim 38, wherein said function is a function of voltage drop and capacitance.

43. The method according to claim 38, further comprising determining that an electrode is defective if its calculated results exceeds fixed upper and/or lower limits.

39-1. The method according to claim 38, wherein said function is a linearity function of the slope of said voltage drop measurements.