Retina implant project [Elektronische Ressource] : chronic implantation of active epiretinal implants / by Eduardo Büchele Rodrigues

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• Gesundheit

Informations

• Publié par: philipps-universitat_marburg
• Publié le: 01 janvier 2004
• Nombre de lectures: 9
• Langue: English
• Poids de l'ouvrage: 7 Mo

Extrait

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Retina Implant Project
Chronic Implantation of Active Epiretinal Implants









Dissertation

in partial fulfillment of the requirements
for the degree of

DOCTOR IN MEDICINE





by

Eduardo Büchele Rodrigues



Department of Ophthalmology
Philipps-University Marburg


October, 2003

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Statement of originality


“I hereby declare that this submission is my own work and that, to the best of my
knowledge and belief, it contains no material previously published or written by another
person nor material which to a substantial extent has been accepted for the award of any
other degree or diploma of this university or other institute of higher learning, except where
due acknowledgement has been made in the text. The animals experiment that provided the
data for the investigations in this dissertation were jointly conducted with PD Dr. Lutz Hesse
and Dr. Thomas Schanze”.





Eduardo Büchele Rodrigues
06/11/2003


















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CONTENTS - INDEX
Page
1. Introduction

1.1 Normal Vision.............................................................................................................................. 5
1.1.1 Eye And Visual System...................................................................................................... 5
1.1.1.1 Structural anatomy of the eye............................................................................ 5
1.1.1.2 Morphology of the retina........................................................ 6
1.1.1.3 Structure organization of the visual system..................................................... 8
1.1.1.4 Eye morphology and visual system of cats........................................ 11

1.2 Abnormal vision........................................................................................................................... 16
1.2.1 Blindness at the level of optic nerve and visual cortex................................................. 16
1.2.2 Retinal diseases leading to blindness.................................................... 17
1.2.3 Retinal diseases leading to blindness by damage to the photoreceptors and retinal
pigment epithelium............................................................................................................. 17
1.2.3.1 Retinitis pigmentosa............................................................................................ 17
1.2.3.2 Age-related macular degeneration......................................... 18
1.2.3.3 Other degenerative retinal diseases................................................................... 20

1.3 Vitreous body and lens surgery – the approach for the epiretinal array implant... 21

1.3 Compensation of blindness by microelectronic devices – visual prosthesis............ 23
1.4.1 Historical review of the initial experiments of visual stimulation in blind patients. 23
1.4.2 The use of electrical energy to create a visual prosthesis.............................................. 24
1.4.2.1 Correcting blindness with electronic devices at the level of the visual
cortex and the optic nerve.................................................................................. 26
1.4.2.1.1 Visual cortex prosthesis.................................................................... 26
1.4.2.1.2 Optic nerve prosthesis.......................................... 29
1.4.2.2 Restoring blindness with retinal prosthesis...................................................... 31
1.4.2.2.1 Epiretinal implants............................................................................ 34
1.4.2.2.2 Subretinal Implants............................................... 37

1.5 This work....................................................................................................................................... 39

2.Objectives.................................................................................................................................................. 41

3. Materials, Method and Procedures.................................................................................................. 42
3.1 Animal Model...............................................................................................................................
3.2 Epiretinal implant specifications................................................. 43
3.3 In-vitro testing of electrical stimulation under intraocular liquids.............................. 47
3.4 Anesthesic and implantation surgical procedure.............................................................. 49
3.5 Clinical follow-up............................................................................................ 54
3.6 Electrical stimulation and data analysis............................................................................... 55

4. Results........................................................................................................................................................ 57
4.1 In-vitro testing of the epiretinal implant functioning under different intraocular
Liquids............................................................................................................................................ 57
4.2 Implantation surgery......................................................... 59
4.3 Positioning of the epiretinal implant..................................................................................... 65
4.4 Influence of the implant on the eye tissues and clinical follow-
up - biocompatibility issue....................................................................................................... 68
4.5 Epiretinal implant function - electrical stimulation and evoked cortical
responses........................................................................................................................................ 74

5. Discussion.............................................................................................................................................. 77
5.1 General remarks...........................................................................................................................
5.2 In-vitro testing of electrical stimulation under intraocular liquids.............................. 78
5.3 Surgical technique and epiretinal implant fixation........................................................... 80
5.3.1 Vitrectomy, phacoemulsification and implantation....................................................... 80
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5.3.2 Vitreoretinal interface cleaning and microelectrode array contact.............................. 82
5.3.3 Implant fixation and final position of the epiretinal implant......................... 84
5.3.3.1 Heavy liquids........................................................................................................ 86
5.3.3.2 Biochemical fixation.................................................. 88
5.3.3.3 Bioadhesives......................................................................................................... 90
5.3.3.4 Tacks.............................................................. 91
5.3.3.5 Suturing................................................................................................................. 92
5.3.3.6 Others............................................................ 93
5.3.3.7 The future and solutions to fixate an epiretinal implant................................ 94

5.4. The epiretinal implant and the reaction of the ocular tissues –
the biocompatibility issue......................................................................................................... 95
5.4.1 Intraocular positioning of the epiretinal implant........................................................... 95
5.4.2 Epiretinal implant related intraocular damage.................................... 96
5.4.2.1 Mechanical trauma............................................................................................... 97
5.4.2.2 Intraocular inflammation.......................................... 98
5.4.2.3 Infection................................................................................................................ 99
5.4.2.4 Epiretinal implant materials biocompatibility.................................................. 100
5.4.2.5 Electrical and heat intraocular injury................................................................ 102
5.5 Future perspectives in the development of a retinal prosthesis..................................... 104

6. Conclusions............................................................................................................................................ 105

7. Bibliography.......................................................................................................................................... 107

8. Résumé – Summary............................................................................................................................. 118

9. Ack