Ophthalmology for the Equine Practitioner

Contents Section 1 General Anatomy and Physiology of the Horse Eye Introduction 3 Some Helpful Hints 3 Anatomy Orbit 4 Eyelids 6 Nictitans 8 Conjunctiva 8 Anterior Segment 8 Precorneal Tear Film 8 Cornea, Limbus, Sclera 9 Iridocorneal Angle 11 Uvea 11 Iris 11 Pupil 12 Ciliary Body 13 Choroid 13 Lens 13 Posterior Segment 14 Vitreous Chamber 14 Retina 14 Optic Nerve 15 Section 2 Examination of the Eye of the Horse History 18 Ophthalmic Examination 18 Reflex Testing 18 Diagnostic Testing 19 What does the Horse See? Visual Capabilities of the Horse 33 Ocular Problems in the Foal 36 Section 3 The Equine Orbit Orbital Diagnostic Techniques 48 Orbital Trauma, Contusion and Periorbital Fractures 50 Foreign Bodies can lead to Orbital Abscesses 52 Orbital Tumors 52 Suture Line Periostitis 54 Treatment of Equine Orbital Disease 54 Section 4 The Eyelids, Conjunctiva and Lacrimal System Traumatic Eyelid Lacerations 60 Neoplasia of the Lids 65 The Conjunctiva 72 Nictitans 76 The Nasolacrimal System 77 Keratoconjunctivitis Sicca (KCS) 78 Dacryocystitis 79 Section 5 Corneal Ulceration Corneal Ulceration 86 Proteinases in the Tear Film 112 Corneal Sensitivity in Foals and Adult Horses 113 Corneal Healing in the Horse 114 The Equine Corneal Microenvironment 115 Medical Therapy 118 Antibiotics 119 Collagenolysis Prevention 119 Treat Uveitis 120 Adjunctive Surgical Therapy 120 **Important Concepts** 127 Corneal Lacerations/Perforations 128 Fungal Ulcers in Horses 130 Iris Prolapse in the Horse 131 Corneal Stromal Abscesses 132 Section 6 Other Corneal Problems Corneal Edema 154 Squamous Cell Carcinoma and other Corneal Tumors 154 Corneal Foreign Bodies 156 Endothelial Detachment following Blunt Trauma 158 Nonulcerative Keratouveitis (NKU) 158 Nonulcerative Interstitial Keratitis (NIK) 158 Eosinophilic Keratoconjunctivitis 160 Herpes and Viral Keratitis 162 Burdock Pappus Bristle Keratopathy 164 Calcific Band Keratopathy 164 Section 7 Cataracts, Glaucoma and Uveal Problems in the Horse Cataracts 170 Equine Cataract Surgery 175 Extracapsular Cataract Surgery 175 Phacoemulsification Cataract Surgery 175 Intracapsular Cataract Surgery 179 Postoperative Cataract Surgery Therapy and Results 179 Aphakic Vision in Horses 180 Equine Glaucomas 181 Contraindications/Possible Interactions 189 Tips on Tonometry for Evaluation of Intraocular Pressure (IOP) in Horses 189 The Uveal Tract 190 Heterochromia Iridis 190 Aniridia/Iris Hypoplasia/Enlarged Corpora Nigra/Iris Colobomas 191 Iris and Ciliary Body Cysts 191 Equine Recurrent Uveitis (Periodic Ophthalmia, Moon Blindness, Iridocyclitis 192 ERU Therapy 200 Some Horses require Life-Long Therapy! 200 Alternative Therapy for ERU 203 Surgical considerations for ERU 203 Section 8 Retinopathies and Ocular Manifestations of Systemic Diseases in the Horse Retinopathies 208 Chorioretinitis 208 Congenital Stationary Night Blindness 211 Equine Motor Neuron Disease Retinopathy 211 Retinal Detachments 211 Optic Neuropathies 213 Bacterial Infections 219 Viral Infections 221 Chlamydial Infections 223 Fungal Infections 223 Protozoan Infections 224 Neoplasia 224 Unknowns 225 Eye Diseases associated with Specific Horse Breeds 226 Links 229 Electroretinography 229 Lavage Treatment Systems 231 Glossary of Selected Veterinary Ophthalmic Terms 232 Treatment Plans/Practice Tips 240 Index 255