OCULAR ANATOMY 12TH BIANNUAL WILLIAM MAGRANE BASIC SCIENCE COURSE 2016 NCSU BRUCE H. GRAHN, DVM, DIPLOMATE, ABVP & ACVO PROFESSOR DEPT. SMALL ANIMAL CLINICAL SCIENCES, ASSOCIATE DEAN ACADEMIC WESTERN COLLEGE OF VETERINARY MEDICINE UNIVERSITY OF SASKATCHEWAN SASKATOON, SASKATCHEWAN CANADA OBJECTIVES FOR OCULAR ANATOMY LECTURES JUNE 6TH 2016 • Understand ocular anatomy at a gross, subgross, and histologic levels. • Understand the embryologic origin of each of the ocular tissues. • Understand the physiology of ocular tissues at an introductory level. • Understand topographic extraocular and intraocular anatomy. • Review pertinent species anatomic differences. • Review the histologic anatomy of common domestic species in a laboratory session. • Review the neuro-ophthalmic examination and the afferent and efferent nerve pathways and their targets. • Provide self evaluation of your anatomic knowledge by short quizzes that may guide your study patterns. • Disclosures: Figures are derived from a variety of sources as identified on the individual power points, and the gross and subgross and histologic figures not referenced are originals and most are copyrighted by Wiley: Histologic Basis of Ocular Disease, Grahn, Wilcock, Peiffer (publishing date early 2017) OUTLINE FOR FIRST 2 HOURS • TOPOGRAPHIC ANATOMY AND THE NEURO-OPHTHALMIC EXAMINATION • ORBITAL NERVE ANATOMY (DOG, CAT, HORSE, COW, PIG, RABBIT) • OCULAR ARTERIAL BLOOD SUPPLY (DOG, CAT, HORSE, COW, PIG, RABBIT) • OCULAR VENOUS DRAINAGE (DOG, CAT, HORSE, COW, PIG, RABBIT) • GENERAL OCULAR ANATOMY (EYELIDS, CORNEA, SCLERA, ANTERIOR AND POSTERIOR SEGMENTS, OCULAR TISSUE HISTOLOGIC INTRODUCTION) • BREAK TOPOGRAPHIC OCULAR ANATOMY WHAT YOU NEED TO KNOW AS AN OPHTHALMOLOGIST AT A GLANCE • Distant exam in photopic & scotopic conditions. • Done at arms length in room light and with a trans illuminator in room light and scotopic conditions with minimum hand restraint . • Note eyelid position of all three eyelids on each side, pupil symmetry and compare pupil size in both light (scotopic & photopic) levels, and attempt to determine if the globes are of similar size (i.e. is there buphthalmos, microphthalmia, exophthalmos, enophthalmos, microblepharon, macroblepharon, blepharospasm, third eyelid prolapse, etc. THE UNDERSTANDING OF TOPOGRAPHIC ABNORMALITIES (EXTRAOCULAR CLINICAL SIGNS) STARTS WITH THE NEURO- OPHTHALMIC EXAMINATION • PALPEBRAL REFLEXES • MENACE RESPONSES • DIRECT PUPILLARY REFLEXES • INDIRECT PUPILLARY REFLEXES • VESTIBULAR OCULAR REFLEXES • SWINGING FLASHLIGHT TEST • CORNEAL REFLEXES • DAZZLE REFLEXES Modified from Grahn/Spiess, EBook, Ocular Disorders of Companion Animals (Diagnosis, Medical and Surgical Therapies THE NEURO-OPHTHALMIC EXAMINATION (GET PHOTOS OF FORAMEN AND CANAL) • PALPEBRAL REFLEX: AFFERENT NERVE - • INDUCE THIS REFLEX BY TOUCHING THE OPHTHALMIC BRANCH OF CNV, (VIA ORBITAL FORAMEN, ENTERS BRAIN STEM CONNECTS TO LOWER EYELID VENTRAL TO THE MEDIAL FACIAL NERVE NUCLEI EFFERENT NERVE IS CRANIAL AND THEN THE LATERAL CANTHI OF BOTH NERVE VII EXITS MEDULLA OBLONGATA ENTERS EYES. INTERNAL ACOUSTIC MEATUS OF THE PETROSAL BONE WITH VESTIBULAR COCHLEAR NERVE THEN IT • ABNORMALITIES IN ANY OF THE TISSUES ENTERS THE FACIAL CANAL AND EXITS AND EFFERENT SENSATION RUNS IN THE ALONG THESE PATHS MAY INDUCE A AURICULOPALPEBRAL NERVE AND INTO THE NEGATIVE PALPEBRAL REFLEX PALPEBRAL NERVE TO THE ORBICULARIS OCULI MUSCLE. THE NEURO-OPHTHALMIC EXAMINATION (GET PHOTO OF FORAMEN AND CANAL) • MENACE RESPONSE: AFFERENT CRANIAL • THIS IS A LEARNED RESPONSE WHICH IS NERVE II EXITS POSTERIOR POLE AND ABSENT IN NEONATAL ANIMALS. FALSE TRAVERSES THE ORBIT, ENTERS OPTIC POSITIVES ARE COMMON IN BLIND FORAMEN, ENTERS THE BASE OF BRAIN AND ANIMALS AND FALSE NEGATIVES ARE CROSSES (OPTIC CHIASMA) SENDS FIBERS TO VISUAL CORTEX AND CONNECTS TO CRANIAL COMMON IN MORIBUND ANIMALS. MAZE NERVE VII NUCLEI AND PASSES THROUGH EVALUATIONS IN SCOTOPIC AND PHOTOPIC PETROSAL BONE AS DESCRIBED FOR THE CONDITIONS AND OCULAR TRACKING OF PALPEBRAL REFLEX AND IT INNERVATES THE LASERS AND TOYS ETC. WILL ASSIST YOU ORBICULARIS OCULI MUSCLE. WITH THE FALSE NEGATIVES AND POSITIVES. THE NEURO-OPHTHALMIC EXAMINATION • DIRECT PUPILLARY LIGHT REFLEX: BRIGHT • INDIRECT PUPILLARY LIGHT REFLEX: SAME PATHWAY, ONLY PRESENT DUE TO OPTICAL LIGHT STIMULATES PHOTORECEPTORS – CHIASMA CROSS OVER (BIRDS REPTILES DO NOT GANGLION CELLS – OPTIC NERVE – THROUGH HAVE AS THEY CROSS 100%), HOWEVER A OPTIC FORAMEN TO CHIASMA TO THE PSEUDO-INDIRECT REFLEX CAN BE ACTIVATED IN SPECIES WITH THIN ORBITAL BONES WHERE THE PRETECTAL NUCLEI – EDINGER WESTPHAL LIGHT SHINES THROUGH THE ORBITAL TO THE NUCLEI – PARASYMPATHETIC FIBERS VIA CONTRALATERAL EYE. NOTE FISH DO NOT HAVE CRANIAL NERVE III – ORBITAL FORAMEN – EITHER, THEY LACK IRIDAL MUSCLES. MANY COMMON FACTORS AFFECT THE PLR AND INCLUDE LEAVE CNIII SYNAPSE AT CILIARY GANGLION – IRIDAL ATROPHY, FEAR, SYNECHIAE, TOPICALLY CILIARY NERVE – IRIS CONSTRICTOR MUSCLE. APPLIED MYDRIATICS ETC. THE NEURO-OPHTHALMIC EXAMINATION • SWINGING FLASHLIGHT TEST (SFT): SIMPLY A • CORNEAL REFLEX: TOUCH CORNEAL SURFACE MODIFICATION OF THE PLR SOME SAME NERVES AND PATHWAYS. WITH COTTON SWAB – AFFERENT SENSATION • INDUCED WHEN A LIGHT IS DIRECTED BACK AND FORTH THROUGH THE OPHTHALMIC BRANCH OF CN FROM PUPIL TO PUPIL. A SMALL PUPILLARY ESCAPE V THROUGH THE ORBITAL FORAMEN TO BRAIN (DILATION AND THEN CONTRACTION) IS EXPECTED IN STEM WITH REFLEX ACTIVATION OF CN VII THE CONTRALATERAL EYE AND THE LIGHT IS PRESENT TO THE FELLOW EYE. EXITS VIA FACIAL CANAL TO PALPEBRAL NERVE • A POSITIVE SFT IS PUPILLARY DILATATION IN THE AND ORBICULARIS OCULI MUSCLE AND CN VI CONTRALATERAL EYE DURING DIRECT ILLUMINATION VIA ORBITAL FORAMEN TO RETRACTOR BULBI. AND CONFIRMS AN AFFERENT PUPILLARY DEFECT (RETINA – OPTIC NERVE LESION). THE NEURO-OPHTHALMIC EXAMINATION • VESTIBULAR OCULAR REFLEXES: THIS IS A • THIS REFLEX IS INDUCED (AFFERENT PATHWAY) COMPLEX REFLEX AND AN IMPORTANT ONE BY THE VESTIBULAR CANAL MOTION VIA CN FOR ASSESSING EXTRAOCULAR MOTILITY VIII WITH NEURONS THAT ACTIVATE (EFFERENT PATHWAY) THE NUCLEI OF ABDUCENS AND AND CRANIAL NERVES 3, 4 AND 6 PLUS THE OCULOMOTOR AND TROCHLEAR NERVES VESTIBULAR SYSTEM (CRANIAL NERVE 8 AND EXTEND THROUGH THE ORBITAL FISSURE (CAT THE MEDIAL LONGITUDINAL FASCICULUS). DOG HORSE) ORBITOROTUNDUM (BOVINE) TO INDUCED BY MOVING THE HEAD SIDE TO THE THEIR RESPECTIVE EXTRAOCULAR MUSCLES SIDE AND UP AND DOWN. VI – LATERAL RECTUS, IV – DORSAL OBLIQUE, III – REST OF THE EXTRAOCULAR MUSCLES. THE NEURO-OPHTHALMIC EXAMINATION • DAZZLE REFLEX: THIS IS A SUBCORTICAL • PATHWAYS: RETINA – OPTIC NERVE (VIA REFLEX THAT IS ACTIVATED BY A BRIGHT OPTIC FORAMEN) TO ROSTRAL COLLICULUS (PAINFUL LIGHT) THAT INDUCES PALPEBRAL – SUPRAOPTIC NUCLEI – THALAMUS – CN VII CLOSURE OF THE IPSILATERAL EYE (SLIGHT – ORBICULARIS OCULI MUSCLE. CLOSURE OF CONTRALATERAL EYE. FINAL COMMENTS ON NEURO-OPHTHALMIC EXAMINATIONS AND NEUROANATOMIC PATHWAYS AS THEY RELATE TO TOPOGRAPHIC EXTRAOCULAR ANATOMY • THIS IS STEP TWO IN THE OPHTHALMIC • NEXT ASSESS WITH TRACKING DEVICES EXAMINATION (DISTANT EXAM IS STEP ONE). (LASERS, TOYS, COTTON BALLS). • WHEN MASTERED THE NEURO-OPHTHALMIC • REMEMBER THAT CHRONIC VISION LOSS IS EXAMINATION TAKES ONLY SECONDS AND IS ACCOMMODATED IN ANIMALS AND SOUND QUINTESSENTIAL FOR ACCURATE DIAGNOSES IN ALL OPHTHALMIC CASES. AND AIR ACTIVATION OF HAIRS DURING THE MENACE RESPONSE CAN LEAD TO FALSE • VISUAL ASSESSMENT IS CHALLENGING IN ANIMALS CONCLUSIONS. AND WHEN THERE ARE HISTORICAL AND THERE IS NEURO-OPHTHALMIC EXAMINATION EVIDENCE OF • FINALLY KNOW YOUR NEURO-ANATOMIC VISUAL IMPAIRMENT COMPLETE A PHOTOPIC AND PATHWAYS AS THIS WILL FACILITATE YOUR SCOTOPIC MAZE TEST. DIAGNOSTIC APPROACH. TOPOGRAPHICAL ANATOMY QUIZ • WHAT ABNORMALITIES ARE PRESENT? • THE ANIOSCORIA WORSENS IN SCOTOPIC CONDITIONS (RIGHT PUPIL REMAINS SMALL LEFT DILATES). • WHAT COMMON OCULAR DISORDERS COULD INDUCE THESE TOPOGRAPHIC ANATOMIC CHANGES? • HOW DO YOU DIFFERENTIATE THESE CONDITIONS? • WHAT ANATOMIC REGIONS COULD BE INVOLVED? ORBITAL NERVES OF THE DOG • CN II – FROM THE CHIASM THROUGH OPTIC FORAMEN TO THE RETINAL GANGLION CELLS • CN III – FROM MID BRAINSTEM THROUGH THE ORBITAL FISSURE AND MAIN TRUNK LIES LATERAL TO THE OPTIC NERVE SUPPLIES ALL RECTUS MUSCLES EXCEPT LATERAL RECTUS, ALSO SUPPLIES VENTRAL OBLIQUE • CN IV – FROM LOWER BRAINSTEM THROUGH THE ORBITAL FISSURE WITH SUPRAORBITAL NERVE ALONG THE SUPERIOR RECTUS MUSCLE AND INNERVATES THE SUPERIOR OBLIQUE. • CN V – FROM MEDULLA AND HAS THREE BRANCHES: MAXILLARY IS MOTOR AND ARRIVES THROUGH THE FORAMEN ROTUNDUM, OPHTHALMIC BRANCH ENTERS ORBIT VIA THE ORBITAL FISSURE AND THE MANDIBULAR BRANCH COMES THROUGH THE FORAMEN OVALE. • CN VI – FROM MEDULLA THROUGH THE ORBITAL FISSURE TRAVELS LATERAL TO TROCHLEAR NERVE INNERVATES RETRACTOR BULBI AND LATERAL RECTUS Figure from Prince et al 1960, Anatomy and histology of the eye and orbit in Domestic animals (Charles C Thomas Publisher) ORBITAL NERVES OF THE CAT • SLIGHT VARIATIONS IN ORBITAL POSITION AND WHERE BRANCHES ARE FOR THE ORBITAL NERVES BUT GENERALLY VERY SIMILAR TO THE DOG AND HORSE WITH EXCEPTION THAT THE SUPRAORBITAL IS NOT ALWAYS PRESENT IN THE CAT. Figure from Prince et al 1960, Anatomy and histology of the eye and orbit in Domestic animals (Charles C Thomas Publisher). ORBITAL NERVES OF THE HORSE • GENERALLY VERY SIMILAR TO DOG AND CAT u Figure from Prince et al 1960, Anatomy and histology of the eye and orbit in Domestic animals (Charles C Thomas Publisher). ORBITAL NERVES OF THE COW • SIGNIFICANT DIFFERENCE IN CATTLE FROM