Chronically implantable retinal prosthesis

• US 6,324,429 B1
• Filed: 05/07/1999
• Issued: 11/27/2001
• Est. Priority Date: 05/08/1998
• Status: Active Grant

• Current Assignee: Massachusetts Eye And Ear Infirmary (Foundation of The Massachusetts Eye and EAR Infirmary Incorporated), Massachusetts Institute of Technology
• Original Assignee: Massachusetts Eye And Ear Infirmary (Foundation of The Massachusetts Eye and EAR Infirmary Incorporated), Massachusetts Institute of Technology
• Inventors: Wyatt, John, Rizzo, Joseph, Shire, Doug
• Primary Examiner(s): Bockelman, Mark
• Application Number:
  US09/306,964
• Time in Patent Office: 935 Days
• Field of Search: 607/53, 607/54, 607/116, 623/6.63
• US Class Current: 607/54
• CPC Class Codes: A61F 2/14 Eye parts, e.g. lenses, corneal implants; Implanting instruments specially adapted therefor; Artificial eyes
• CPC Class Codes: A61F 2/15 Implant having one or more holes, e.g. for nutrient transport, for facilitating handling
• CPC Class Codes: A61F 2250/0001 Means for transferring electromagnetic energy to implants
• CPC Class Codes: A61N 1/0543 Retinal electrodes
• CPC Class Codes: A61N 1/36046 of the eye

Abstract

A combination of silicon processing technology advances and increased understanding of the mechanisms underlying phosphene generation in human retinas by surface electrical stimulation has now made it possible to conceive of a chronically implantable retinal prosthesis for the blind which will restore some useful vision to patients over at least several degrees of their former field of view. These thin, strong, and flexible epiretinal devices are constructed of or encapsulated in known biocompatible materials which will have a long working life in the eye'"'"'s saline environment. The function of the implants is to electrically stimulate the ganglion cell layer at the surface of the retina using controlled current sources. Due to the exceptionally low mass of the implant and its flexible, nearly planar form, patient discomfort and fluid drag caused by the implant minimized. These physical atttributes also substantially reduce the potential of harm to the most delicate structure of the eye, the retina, and therefore enhance the long term safety and biocompatibility of the device. Since no micro-cables are required to be attached to the device, and its overall form and edges are rounded, the device is not expected to stress the retina during chronic implantation. A provision is also made for nutrients to reach the retinal cells underneath the device to assure their long-term health.

Claims

1. An apparatus in contact with the inner surface of the retina, comprising:

means to physically and conformally contact the retina surface with a flexible, strong multilayered, substantially planar structure, comprising;

a thin semiconductor layer containing CMOS circuitry;

a thin insulating layer disposed over at least a portion of the surface of the apparatus;

stimulating electrodes disposed on the surface of the apparatus;

stress-compensated passivation layers disposed about at least a portion of the apparatus, which enhance the apparatus'"'"' biocompatibility;

means to receive power and data for said circuitry from outside the patient'"'"'s body via electromagnetic radiation; and

means to transmit said power and data signals

wherein the apparatus electrically stimulates at least a portion of the surface of the retina.

2. The apparatus of claim 1, wherein

said multilayered structure is monolithically integrated; and

said multilayered structure is suited to mass production using common microfabrication equipment.

3. The apparatus of claim 1, wherein said thin semiconductor layer is the surface active layer of a silicon-on-insulator structure.

4. The apparatus of claim 3, wherein said stress-compensated passivation layers comprise a material from the group consisting of silicon oxide and nitride, and further comprise a surface layer of plasma-deposited amorphous silicon carbide.

5. The apparatus of claim 1, wherein said stimulating electrodes comprise iridium which has been activated and oxidized by cyclic voltammetry.

6. The apparatus of claim 1, wherein said stimulating electrodes comprise of titanium nitride which has been activated and oxidized by cyclic voltammetry.

7. The apparatus of claim 1, wherein said insulating layer comprises a polyimide.

8. The apparatus, of claim 7, wherein the polyimide comprises PIQ-L100 as provided by HD Microsystems, Inc.

9. The apparatus of claim 7, wherein the surface of said polyimide layer is modified by ion bombardment to enhance the biocompatibility of the material.

10. The apparatus of claim 7, wherein said polyimide layer is modified at its surface using chemicals from the group consisting of growth factors, anti-inflammatory factors, and anti-angiogenic factors.

11. The apparatus of claim 1, wherein said electromagnetic radiation has a wavelength between 400 and 700 nm and wherein said means to receive power and data comprises a photodiode array monolithically integrated with the remainder of the CMOS circuitry, and wherein said means of transmitting power is a laser.

12. The apparatus of claim 1, wherein said thin semiconductor layer and said thin insulating layer are perforated with holes wherein nutrients are allowed to reach the retinal cells covered by said apparatus.

13. The apparatus of claim 1, wherein said thin insulating layer containing said stimulating electrodes is connected to said thin semiconductor layer containing CMOS circuitry by means of an extension of said thin insulating layer and conductive traces contained therein, thereby allowing said power and data for said circuitry to be received at a location remote from the region to be stimulated.

14. The apparatus of claim 13, wherein said remote location is the lens of the eye.

15. The apparatus of claim 13, wherein said remote location is in the anterior portion of the eye and in contact with the retina surface.

16. The apparatus of claim 1, wherein said electromagnetic radiation has a wavelength between 1 m and 1 km and said means to receive and transmit power and data comprise inductive coils.

17. The apparatus of claim 1, wherein the force exerted by the apparatus on the retina is not greater than 10 mm Hg.