Aus dem Zentrum für klinische Tiermedizin Tierärztliche Fakultät der Ludwig – Maximilians - Universität München Arbeit angefertigt unter Leitung von Prof. Dr. R. Korbel IMAGING OF PHYSIOLOGICAL RETINAL STRUCTURES IN VARIOUS RAPTOR SPECIES USING OPTICAL COHERENCE TOMOGRAPHY (OCT) Inaugural - Dissertation zur Erlangung der tiermedizinischen Doktorwürde der Tierärztlichen Fakultät der Ludwig – Maximilians - Universität München vorgelegt von María Luisa Velasco Gallego aus Valladolid München 2015 Aus dem Zentrum für klinische Tiermedizin der Tierärztlichen Fakultät der Ludwig-Maximilians-Universität München Lehrstuhl für aviäre Medizin und Chirurgie Arbeit angefertigt unter der Leitung von Prof. Dr. R. Korbel Mitbetreuung durch: Priv.-Doz. Dr. Monika Rinder Gedruckt mit Genehmigung der Tierärztlichen Fakultät der Ludwig-Maximilians-Universität München Dekan: Univ.-Prof. Dr. Joachim Braun Berichterstatter: Univ.-Prof. Dr. Rüdiger T. Korbel Korreferent/en: Priv.-Doz. Dr. Sven Reese Tag der Promotion: 31. Januar 2015 A mi querida familia y a Edu INDEX INDEX .......................................................................................................................... V LIST OF ABBREVIATIONS .......................................................................................... IX 1 INTRODUCTION ................................................................................................ 1 2 LITERATURE ..................................................................................................... 3 2.1 Optical Coherence Tomography (OCT) ....................................................... 3 2.1.1 Physical and technical baselines of OCT ............................................. 4 2.1.1.1 Theoretical fundaments of OCT ........................................................ 5 2.1.1.1.1 Low coherence interferometry .................................................... 5 2.1.1.1.2 Resolution .................................................................................. 7 2.1.2 OCT systems ....................................................................................... 8 2.1.2.1 Time Domain OCT ........................................................................... 8 2.1.2.2 Spectral Domain OCT ...................................................................... 9 2.1.2.3 OCT systems development ............................................................ 11 2.1.2.3.1 Resolution improvement .......................................................... 11 2.1.2.3.2 Imaging speed improvement .................................................... 12 2.1.2.3.3 Speckle reduction .................................................................... 13 2.1.2.3.4 Eye-Tracking system ............................................................... 13 2.1.2.3.5 En-Face OCT systems ............................................................. 14 2.1.2.3.5.1 Indocyanine-Green-Angiography in combination with UHR- OCT/SLO .......................................................................................... 17 2.1.2.3.5.2 Full-field OCT .................................................................... 17 2.2 Anatomy of the avian eye .......................................................................... 18 2.2.1 Adnexal structures ............................................................................. 18 2.2.2 Orbit ................................................................................................... 19 2.2.3 Extraocular muscles ........................................................................... 19 2.2.4 Globe ................................................................................................. 20 2.2.5 Retina ................................................................................................ 26 2.2.5.1 Anatomy and physiology of the avian retina ................................... 26 2.2.5.1.1 Pecten ..................................................................................... 26 2.2.5.1.2 Areae and Foveae ................................................................... 27 2.2.5.1.3 Retinal layers ........................................................................... 28 2.3 Ultrahigh Resolution Spectral-Domain OCT (UHR-SD-OCT) ..................... 30 2.3.1 Indications and applications ............................................................... 30 2.3.1.1 OCT in human medicine and research ........................................... 31 2.3.1.1.1 Retinal thickness measurement ............................................... 32 2.3.1.1.2 Glaucoma ................................................................................ 33 2.3.1.1.3 Diabetic retinopathy ................................................................. 33 2.3.1.1.4 Objective assessment of macular hole ..................................... 34 2.3.1.1.5 Vitreo-retinal evaluation ........................................................... 34 2.3.1.1.6 Intraoperative OCT .................................................................. 34 2.3.1.1.7 Anterior Segment OCT (AS-OCT) ............................................ 35 2.3.1.1.8 Progress monitoring of retinal vasculopathies .......................... 35 2.3.1.2 OCT in veterinary medicine and research....................................... 35 2.3.1.2.1 OCT in avian ophthalmology .................................................... 37 2.4 SD-OCT Reflectance patterns ................................................................... 39 2.4.1 Bird-eye-specific reflectance patterns and OCT imaging .................... 42 2.5 Alignment and comparison of histology and UHR-SD-OCT of retinal layers .. .................................................................................................................. 44 2.5.1 Histologic preparation of the eye ........................................................ 45 3 MATERIALS AND METHODS .......................................................................... 47 3.1 Avian patients ........................................................................................... 47 3.2 Clinical examination of the patients ........................................................... 49 3.2.1 General clinical examination .............................................................. 49 3.2.1.1 Anamnesis ..................................................................................... 49 3.2.1.2 Adspection ..................................................................................... 49 3.2.1.3 Physical examination ...................................................................... 50 3.2.1.4 Ophthalmological examination ........................................................ 51 3.2.1.4.1 Instrumentation ........................................................................ 51 3.2.1.4.2 Examination procedure ............................................................ 52 3.3 OCT device and examination .................................................................... 55 3.3.1 OCT device ........................................................................................ 55 3.3.2 OCT examination ............................................................................... 57 3.3.2.1 Preparation and restraint of the patient under examination ............. 57 3.3.2.2 OCT-examination ........................................................................... 58 3.3.2.3 Patient status and care post OCT-examination............................... 62 3.3.2.4 OCT data and images processing .................................................. 63 3.4 Histological examination ............................................................................ 64 3.4.1 Euthanasia of the patient .................................................................... 64 3.4.2 Enucleating of the eyes ...................................................................... 64 3.4.3 Fixation .............................................................................................. 65 3.4.4 Decalcification .................................................................................... 66 3.4.5 Dehydration ........................................................................................ 66 3.4.6 Paraffin embedding ............................................................................ 67 3.4.7 Cutting ............................................................................................... 69 3.4.8 Staining .............................................................................................. 70 3.5 Data processing ........................................................................................ 71 3.5.1 Processing of the OCT-images .......................................................... 71 3.5.2 Processing of the histological sections ............................................... 73 4 RESULTS ........................................................................................................ 75 4.1 OCT-examination of the raptor eye ........................................................... 75 4.1.1 General considerations ...................................................................... 75 4.1.1.1 Intraspecific variations .................................................................... 79 4.1.1.1.1 Accipitriformes ......................................................................... 79 4.1.1.1.2 Falconiformes .......................................................................... 92 4.1.1.1.3 Strigiformes ...........................................................................