Ocular Anatomy 11Th Biannual William Magrane Basic Science Course

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 DOGS CATS AND HORSE AS THEY HAVE AN ORBITAL ROTUNDUM WHICH CONTAINS CN III, CN IV, AND THE MAXILLARY ARTERY.

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 PIG

• ORBITOROTUNDUM PROVIDES PASSAGE FOR ALL THE SOMATIC NERVES INVOLVED IN ORBITAL SENSATION AND MOTOR EXCEPT THE OPTIC NERVE. • CONTAINS OPHTHALMIC BRANCH OF V, CN III, MAXILLARY BRANCH OF V, AND CNVI.

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 RABBIT

• OPTIC NERVE IN RABBITS IS SHORT • CN V MAXILLARY AND OPHTHALMIC BRANCHES EXIT ORBITOROTUNDUM + CNIII, CN IV, AND CN VI.

Figure from Prince et al 1960, Anatomy and histology of the eye and orbit in Domestic animals (Charles C Thomas Publisher). THIRD EYELID

• Anatomy: • Covered with conjunctiva (palpebral & bulbar). • May contain pigment or be non-pigmented. • Central T-shape core of hyaline cartilage that provides support. • A loose fibrous/vascular stroma is present under the conjunctiva and surrounding the cartilage.

• The lacrimal gland of the third eyelid (sero-mucinous) envelopes the stem of the T-cartilage ventrally.

• Embryologic origin of tissues (surface ectoderm, neurocrest mesenchyme, mesoderm).

• Function: protection, distribution of tear film, production of 40% of tear film. UPPER AND LOWER EYELIDS

• ANATOMY: • COVERED BY HAIR. • ANCHORED AT MEDIAL AND LATERAL CANTHI BY RESPECTIVE LIGAMENTS. • CLOSURE IS VIA THE ORBICULARIS OCULI AND VII NERVE. EYELIDS

• DIVERSITY OF EYELID STRUCTURE (FROM NO EYELIDS (FISH, SOME REPTILES), TO THREE EYELIDS WHERE THE NICTITANS ARE ACTIVELY MOVED (AVIAN SPP) AND SOME ARE PASSIVE (DOMESTIC ANIMALS) • BONUS QUIZ: EYELIDS EYELIDS EYELIDS THE ANATOMIC RELATIONSHIP OF THE EYE TO THE EYELIDS IS IMPORTANT! QUIZ: WHAT ABNORMALITIES ARE PRESENT AND WHAT DIFFERENTIALS DO YOU CONSIDER FOR THIS BOVINE AND THIS CAT? EYELID ANATOMY UPPER AND LOWER EYELIDS

• HISTOLOGIC ANATOMY: • INNER SURFACE: LINED BY PALPEBRAL CONJUNCTIVA WHICH CONTAINS GOBLET CELLS WHICH PRODUCE MUCIN (INNER LAYER OF THE TEAR FILM). • TARSAL GLANDS: SEBACEOUS GLANDS THAT LIE ON THE CONJUNCTIVAL SIDE OF THE TARSAL PLATE AND THESE PRODUCE THE OUTER LAYER OF THE TEAR FILM. • EYELID MARGINS SMOOTH AND NORMALLY WITHOUT HAIR AND PERFORATIONS ARE PRESENT (TARSAL GLAND ORIFICES). • OUTER SURFACE COVERED BY HAIR. EYELID MUSCLES

Muscle Function Innervating nerve

Levator palpebrae Raises the upper eyelids CN 3 (oculomotor)

Corrugator. supercilii Raises the upper eyelids CN 7 (facial)

Retractor anguli oculi Tightens the lateral palpebral CN 7 (facial)

fissure

Pars palpebralis Lowers the ventral eyelid CN 7 (facial)

Orbicularis oculi Closes the upper and lower CN 7 (facial)

eyelids

(Modified from Grahn/Spiess, EBook, Ocular Disorders of Companion Animals (Diagnosis, Medical and Surgical Therapies). EYELIDS: FASCIA AND ARTERIAL AND VENOUS BLOOD SUPPLY EYELIDS AND TEAR FILM FUNCTION AND EMBRYOLOGIC ORIGIN

• Function: -protection & tear film distribution -tarsal glands produce oily secretion that lies on top of the tear film and retards evaporation. Eyelids are lined by palpebral conjunctiva that reflects at the fornix and becomes bulbar conjunctiva. Goblet cells in the palpebral conjunctiva produce mucin which assists in anchoring the tear film to the ocular surface. Embryologic origin for eyelids and glands that produce the tear film: surface ectoderm, mesoderm and neural crest mesenchyme. A FEW PERTINENT TOPOGRAPHIC ANATOMIC PERIOCULAR FEATURES

• Ciliary arteries & vortex veins are useful when orientating enucleated globes for sectioning. • Also remember that these are at 3&9 o’clock (ciliary arteries) and at 2:30,4:30, 7:30, 10:30 vortex veins and try to avoid these during surgery! • Generally smaller eyes are round and larger eyes are flatter on the anterior surfaces. GLOBE TOPOGRAPHY THREE PLANES OF SECTION

Samuelson Magrane Anatomy notes/power point ENJOY THE ENDLESS DIVERSITY OF THE TOPOGRAPHIC OCULAR ANATOMY OF THE SPECIES THAT WE EXAMINE A FEW PERTINENT TOPOGRAPHIC INTRAOCULAR ANATOMIC FEATURES (C0NT)

• Topographic retinal features: holangiotic, paurangiotic, merangiotic, and anagiotic fundi. • Optic pits. • Bergermeister’s papilla. • Hyaloid canal. • Mittendorf’s dot. • Locations of optic discs, amount of myelin. • Some optic discs are hidden by pectin, conus papillaris etc. A FEW TOPOGRAPHIC INTRAOCULAR ANATOMIC FEATURES (C0NT)

• UVEA (IRIS, CILIARY BODY (PARS PLICATA, PARS PLANA, ORA SERRATA, OPTIC NERVE. • ANTERIOR SEGMENT. • POSTERIOR SEGMENT. • ANTERIOR CHAMBER. • POSTERIOR CHAMBER. • RETINA, OPTIC DISC. GLOBE TOPOGRAPHY CONTINUED EMBRYOLOGIC TISSUES OF ORIGIN

• SURFACE ECTODERM: CORNEAL AND CONJUNCTIVAL EPITHELIUM, GLANDS (LACRIMAL, NICTITANS, TARSAL GLANDS, ETC.) AND LENS. • NEUROCREST MESENCHYME: CORNEAL STROMA AND ENDOTHELIUM, UVEA, CILIARY MUSCLES. • NEUROECTODERM: RETINA, RETINA PIGMENT EPITHELIUM, CILIARY AND POSTERIOR IRIS EPITHELIUM, IRIDAL MUSCLES. • MESODERM: OCULAR BLOOD VESSELS AND STRIATED MYOCYTES OF EXTRAOCULAR MUSCLES.

Samuelson Magrane Anatomy notes/power point GENERAL COMMENTS ON ARTERIAL BLOOD SUPPLY TO OCULAR TISSUES

• MAIN BLOOD SUPPLY TO EYE AND ORBIT OF DOMESTIC ANIMALS IS VIA THE INTERNAL MAXILLARY ARTERY (A BRANCH OF THE EXTERNAL CAROTID) QUIZ # 3 WHICH FORAMEN DOES THE MAXILLARY ARTERY PASS THROUGH? • INTERNAL MAXILLARY ARTERY GIVES RISE TO EXTERNAL OPHTHALMIC ARTERY AND YOU MAY FOLLOW THE BRANCHES IN THE DIAGRAM PROVIDED • NOTE PRIMATES: THE SOURCE IS MOSTLY THE INTERNAL CAROTID THAT GIVES RISE TO THE INTERNAL OPHTHALMIC • THE INTERNAL CAROTID – INTERNAL OPHTHALMIC ARE MUCH LESS OF A CONTRIBUTOR IN OUR DOMESTIC SPECIES WHERE IT SUPPLIES PARTS OF THE OPTIC NERVE AND THEN IT ANASTOMOSIS WITH THE EXTERNAL OPHTHALMIC ARTERY GENERAL COMMENTS ON THE VENUS DRAINAGE OF THE EYE AND OCULAR TISSUES

• VENOUS DRAINAGE VARIES CONSIDERABLY AMONG DOMESTIC SPECIES. • IN THE DOG THERE ARE TWO MAIN VENOUS CHANNELS (SUPRAORBITAL AND INFERIOR ORBITAL VEINS). • LACRIMAL, VORTEX, ETHMOIDAL AND MUSCULAR VEINS EMPTY INTO THE INFERIOR ORBITAL VEINS WHICH ANASTOMOSE AND THEN JOINS THE SUPRAORBITAL VEIN AT THE APEX OF THE POSTERIOR ORBIT. • ORBITAL VEIN ENTERS THE INTRACRANIAL VENOUS DRAINAGE SYSTEM. • THE INTERNAL MAXILLARY VEIN JOINS THE EXTERNAL JUGULAR VEIN (EXTRACRANIAL DRAINAGE). ORBITAL ARTERIAL AND VENOUS SYSTEMS OF THE ORBIT OF THE DOG

Figures from Prince et al 1960, Anatomy and histology of the eye and orbit in Domestic animals (Charles C Thomas Publisher). ARTERIAL AND VENOUS SYSTEMS OF THE CAT ORBIT

Figures from Prince et al 1960, Anatomy and histology of the eye and orbit in Domestic animals (Charles C Thomas Publisher). NOTE THE UNIQUE VENOUS DRAINAGE IN THE CAT ORBIT

• CATS HAVE AN EXTERNAL VASCULAR • QUIZ 4: THROUGH WHAT FORAMEN DOES NETWORK (RETE). THE OPHTHALMIC VEIN EXIT? • CILIARY VEINS, VORTEX VEINS AND LONG POSTERIOR CILIARY VEINS EMPTY INTO THIS RETE. • THE RETE EMPTIES INTO A LARGE OPHTHALMIC VEIN WHICH ENTERS THE JUGULAR VEIN. • THE SUPRAORBITAL VEIN DRAINS INTO THE FACIAL VEIN AND THEN INTO THE INTERNAL JUGULAR VEIN. ORBITAL ARTERIAL AND VENOUS SYSTEMS OF THE ORBIT OF THE COW

Figures from Prince et al 1960, Anatomy and histology of the eye and orbit in Domestic animals (Charles C Thomas Publisher). GENERAL COMMENTS CONCERNING THE ARTERIAL BLOOD SUPPLY TO OCULAR TISSUES

• THE ARTERIES OF THE RETINA AND CHOROID ARE SUPPLIED BY BOTH THE LONG AND SHORT POSTERIOR CILIARY ARTERIES. • IN MOST DOMESTIC SPECIES A NUMBER OF ARTERIES (SHORT CILIARY ARTERIES) ENTER THE GLOBE AROUND THE OPTIC NERVE AND GIVE RISE TO RETINAL ARTERIOLES THAT SUPPLY THE INNER THIRD OF THE RETINA. • THE OUTER THIRD OF THE RETINA NUTRIENT SUPPLY COMES FROM THE CHOROIDAL ARTERIES THROUGH THE RPE AND INTO THE OUTER RETINA. • THE ANTERIOR CILIARY ARTERIES ENTER THE GLOBE THROUGH THE SCLERA BEYOND THE EQUATOR AND SUPPLY THE IRIS, CILIARY BODY AND ANTERIOR CHOROID. ORBITAL ARTERIAL SYSTEM IN THE HORSE

Figures from Prince et al 1960, Anatomy and histology of the eye and orbit in Domestic animals (Charles C Thomas Publisher). ARTERIAL CASTS OF THE ORBIT OF A HORSE PIG ORBITAL ARTERIAL SYSTEM

Figures from Prince et al 1960, Anatomy and histology of the eye and orbit in Domestic animals (Charles C Thomas Publisher). ORBITAL ARTERIAL AND VENOUS SYSTEM RABBIT

Figures from Prince et al 1960, Anatomy and histology of the eye and orbit in Domestic animals (Charles C Thomas Publisher). LYMPHATIC DRAINAGE LIMITED TO THE EYELIDS

• ALTHOUGH CONTROVERSIAL MOST BELIEVE THE GLOBE AND ORBIT DO NOT HAVE LYMPHATIC DRAINAGE. • EYELID AND CONJUNCTIVAL LYMPHATIC DRAINAGE DOES EXIST AND THEY DRAIN TO THE PAROTID AND THE MANDIBULAR LYMPH NODES. • THESE ARE IMPORTANT TO KNOW AS PERIOCULAR NEOPLASMS WILL METASTASIZE TO THESE AND YOU WILL NEED TO BIOPSY OR FINE NEEDLE ASPIRATE THESE. • QUIZ 6:WHAT ARE H AND I ON THIS ILLUSTRATION?

Miller Christensen and Evans Anatomy of the dog WB Saunders VITREOUS

• PRIMARY VITREOUS: • SECONDARY VITREOUS: • TERTIARY VITREOUS? • EMBRYOLOGIC DERIVATIONS PRESENCE OR LACK OF THE TAPETUM AND UVEAL PIGMENT INTRAOCULAR TISSUE RELATIONSHIPS (GROSS AND SUBGROSS) RELATIONSHIPS OF POSTERIOR SEGMENT TISSUES

• RETINA: • RETINAL PIGMENT EPITHELIUM: • CHOROID: • SCLERA: • QUIZ: EMBRYOLOGIC DERIVATIONS OF THESE TISSUES? LIMBUS, FILTRATION ANGLES, IRIDES CILIARY PROCESSES

• BILAYERS OF EPITHELIUM: • ZONULAE: • FIBROVASCULAR CORE: RETINA AND RETINAL PIGMENT EPITHELIUM OPTIC NERVES GROSS APPEARANCES QUESTIONS AND BREAK

• QUIZ: WHAT ARE THE AFFERENT AND EFFERENT NERVES THAT RESULT IN THE VESTIBULAR OCULAR REFLEX? • WHAT NERVES PASS THROUGH THE ORBITAL FISSURE IN THE HORSE? • WHAT FORAMEN IS IDENTIFIED IN THIS FIGURE? OUTLINE PART II ANATOMY

• ORBITAL BONES, FORAMEN, AND • NASOLACRIMAL SYSTEM. CONTENTS. • ZYGOMATIC SALIVARY GLAND. • EXTRAOCULAR MUSCLES AND THEIR INNERVATION. • THIRD EYELID. • LACRIMAL SYSTEM. ANATOMY OF THE ORBIT

• BONES: FRONTAL, LACRIMAL, ZYGOMATIC, • FORAMEN: ROSTRAL ALAR, ETHMOIDAL, MAXILLARY, PRE-SPHENOID, BASISPHENOID LACRIMAL, OPTIC, ORBITAL ROTUNDUM AND PALATINE. FORAMEN, SUPRAORBITAL. ORBIT

• ORBITAL BONES OF THE DOG AND CAT (Modified from Grahn/Spiess, EBook, Ocular Disorders of Companion Animals (Diagnosis, Medical and Surgical Therapies).

ORBIT

Foramen/Fissure Common. species of animal Nerves/Vessels contained within it • FORAMEN AND CONTENTS VARIES WITH Rostral alar Canine, Equine, Feline Maxillary artery and nerve THE SPECIES OF ANIMAL Ethmoid All common species Ethmoidal vessels/nerve

Orbital Canine, equine, feline Abducens, oculomotor, ophthalmic, and trochlear

nerves.

Orbitorotundrum Bovine Oculomotor, trochlear nerves and internal

maxillary artery

Optic All species Optic nerve and internal ophthalmic artery

Rotundum Canine, equine, feline Maxillary nerve

Supraorbital Bovine, canine, equine (variable in feline) Supraorbital vessels and nerve. FORAMEN OF THE HORSE, COW AND DOG (Modified from Grahn/Spiess, EBook, Ocular Disorders of Companion Animals (Diagnosis, Medical and Surgical Therapies).

EXTRAOCULAR MUSCLES

Muscle Function Innervating nerve supply

Retractor bulbi Globe retraction CN VI (Abducens)

Dorsal oblique Globe torsion towards temple CN IV (Trochlear)

Ventral oblique Globe torsion towards the nasal CN III (Oculomotor)

region

Dorsal rectus Globe elevation CN III (Oculomotor)

Ventral rectus Globe lowering CN III (Oculomotor)

Lateral rectus Globe moves lateral CN VI (Abducens)

Medial rectus Globe moves medial CN III (Oculomotor) THIRD EYELID ANATOMY (SAMUELSON MAGRANE ANATOMY NOTES/POWERPOINT) AVIAN THIRD EYELIDS

Anatomy of the avian orbit. Note the Pyramidalis (8) and Quadratus (7) muscles. CJ Murphy, PhD Thesis 1984. LACRIMAL

(Samuelson Magrane Anatomy notes/power point) NASOLACRIMAL DRAINAGE

• PUNCTUM (PUNCTA) • CANALICULI • LACRIMAL SAC • NASOLACRIMAL DUCT • PHYSIOLOGY (VENTRAL PUNCTA DRAINS MOST, ASSISTED BY GRAVITY AND NEGATIVE INTRACANALICULAR PRESSURE RELATED TO ORBICULARIS OCULI CONTRACTION). ZYGOMATIC SALIVARY GLAND

• LOCATION IN VENTRAL ORBIT OF THE DOG REVIEW OF ORBIT/EYELIDS/LACRIMAL/NASOLACRIMAL OCULAR ANATOMY PART III: GROSS AND HISTOLOGIC ANATOMY OF THE

• CORNEA. • VITREOUS • SCLERA • RETINA • UVEA • RETINAL PIGMENT EPITHELIUM • LENS • OPTIC NERVE CORNEA

• Cornea is the anterior portion of the fibrous tunic. • Most refractive surface of the eye. • Most prone to injury. • Metabolic needs met by tear film, aqueous humor, and limbal blood supply. • Rich nerve supply, devoid of blood vessels and lymphatics normally. • Minimal pigment. CORNEA

• Covered with superficial epithelium and a basement membrane which are derived from surface ectoderm. • Over 90% of the cornea is stroma which mostly collagen secreted by keratocytes, and they are derived from neurocrest tissues. • Lined by the endothelium and Descemet’s membrane, which also originate from neurocrest tissues. Modified from D. Samuelson Ophthalmic Anatomy Notes Magrane Course 2012.

CORNEA

• Thickness of cornea varies with location and within species. • Types of collagen secreted in corneal layers also varies. Animal Corneal thickness centrally Corneal thickness at periphery Location within cornea Collagen type Glycan type

Epithelium IV, VI, VII Laminin, fibronectin, hyaluronin Equine 1-1.5 mm 0.8 mm

Bowman’s layer I, III, V, VI Heparin sulfate Bovine 1.5-2 mm 1.5-1.8 mm

Ovine Stroma I, III, V, VI, XII Chondroitin 4 & 6 sulfates, & 0.8-2.0 mm 0.3-0.5 mm Porcine 1-1.2 mm 0.5-08 mm dermatin sulfate Canine 0.6-1.0 mm 0.5-0.7 mm

Descemet’s membrane I, III, IV, VI, VIII Laminin, fibronectin, tenascin P, Feline 0.8-1.0 mm 0.4-0.6 mm

heparin sulfate CORNEAL EPITHELIUM

• TOUGH OUTER BARRIER WITH MULTIPLE EPITHELIAL LAYERS THAT ARE CONSTANTLY REGENERATING FROM THE BASAL LAYER AND FROM THE LIMBUS. • SURFACE IS TEXTURED SLIGHTLY TO AID IN ADHESION OF MUCOUS PORTION OF THE TEAR FILM. • NOTE THE MORE COLUMNAR BASAL CELLS AND THE BASEMENT MEMBRANE, WING CELLS AND THE FLAT SURFACE EPITHELIAL CELLS IN THIS HISTOLOGIC SECTION. • EMBRYOLOGIC DERIVATION: SURFACE ECTODERM CORNEAL STROMA

• . THE SPECIFIC ARRANGEMENT OF THE COLLAGEN FIBERS IS ABOUT 620-640 ANGSTROM. • THIS ARRANGEMENT IS BELIEVED TO PERMIT APPROXIMATELY 99% OF THE LIGHT ENTERING THE CORNEA TO PASS THROUGH. • COLLAGEN TYPE I IS THE MOST COMMON COLLAGEN THROUGHOUT THE CORNEAL STROMA • EMBRYOLOGIC DERIVATION: NEUROCREST ENDOTHELIUM AND DESCEMET’S MEMBRANE

• DESCEMET’S MEMBRANE IS THE BASEMENT MEMBRANE OF THE ENDOTHELIUM.

• CONTINUALLY SECRETED THROUGHOUT LIFE.

• ANCHORS ENDOTHELIUM TO THE STROMA.

• DESCEMET'S MEMBRANE IS COMPOSED OF COLLAGEN FIBERS.

• IT HAS ELASTIC TENDENCIES ALTHOUGH THERE ARE NO ELASTIN COMPONENTS.

• ULTRA STRUCTURALLY THIS MEMBRANE IS LAYERED IN MOST ANIMALS.

• A RELATIVELY THIN SUPERFICIAL UNBANDED ZONE LIES NEXT TO THE STROMA.

• AN UNBANDED ZONE NEXT TO THE ENDOTHELIUM.

• TYPE III, AND IV COLLAGEN MAKE UP THE POSTERIOR ZONE WHILE TYPES IV AND VIII MAKE UP THE ANTERIOR BANDED ZONE AND TYPES V AND VI THE UNBANDED ZONE.

• EMBRYOLOGIC DERIVATION: NEUROCREST TERMINATION OF DESCEMET’S AND ENDOTHELIUM

• ENDOTHELIAL CELLS HAVE A HEXAGONAL SHAPE WHEN EXAMINED BY ELECTRON MICROSCOPY AND SPECTRAL MICROSCOPY.

• THEY HAVE COMPLEX INNER DIGITATIONS AND THEY ARE TIGHTLY BOUND TO ONE ANOTHER BY ZONULAR OCCLUDENS AND MACULAR ADHERENCE.

• THE ENDOTHELIUM IS GENERALLY VERY METABOLICALLY ACTIVE AND CONTAINS MULTIPLE MITOCHONDRIA AND SMOOTH AND ROUGH ENDOPLASMIC RETICULAE AND A VARIETY OF VESICLES AS THESE CELLS ARE RESPONSIBLE FOR PUMPING FLUID FROM THE CORNEA INTO THE ANTERIOR CHAMBER.

• AS ANIMALS AGE THE ENDOTHELIAL DENSITY DECREASES, FROM APPROXIMATELY 3000 CELLS/MM2 TO LESS THAN 1000 IN OLD DOGS.

• AS THEY DECREASE IN NUMBER, THE MORPHOLOGY OF THE CELLS CHANGES TO A THINNER FLATTENED CELL TYPE.

• GENERALLY IF ENDOTHELIAL COUNTS DROP TO LESS THAN 750 CELLS/MM2 THERE WILL BE INSUFFICIENT CELLULAR PUMPS TO RESIST HYDROSTATIC INTRAOCULAR PRESSURE, AND CORNEAL EDEMA WILL DEVELOP. THE FILTRATION ANGLE OF A HARBOR SEAL THE ALL IMPORTANT LIMBUS AND UNDERLYING FILTRATION ANGLE

• THIS IS A COMMON SURGICAL ENTRY POINT TO THE ANTERIOR SEGMENT. • THE LIMBUS FORMS THE OUTER PORTIONS OF THE FILTRATION ANGLE. • DESCEMET’S’ MEMBRANE TERMINATES HERE. • LIMBAL STEM CELLS ORIGINATE HERE. • THE PRECISE ORGANIZATION OF STROMAL COLLAGEN BUNDLES IS LOST, THE EPITHELIUM THICKENS AND THEN ABRUPTLY TRANSITIONS TO A THINNER CONJUNCTIVAL MUCOUS MEMBRANE, AND PIGMENTED CELLS, AND BLOOD VESSELS AND NERVES ARE FREQUENTLY ENCOUNTERED. SCLERA (Modified from Grahn/Spiess, EBook, Ocular Disorders of Companion Animals (Diagnosis, Medical and Surgical Therapies).

SCLERA

Animal Center mm Near optic nerve mm Equator mm Limbus mm • THIS FIBROUS TUNIC MERGES WITH THE CORNEA AT THE LIMBUS AND IS VARIABLY PIGMENTED. Horse 1.5-2.2 1.35 0.3- 0.5 1.1

Cow • THERE ARE CONSIDERABLE VARIATIONS IN 1.9 2.2 1.0 1.2-1.5 THE SCLERA AMONGST THE SPECIES. Sheep 1.0-1.2 1.2 0.25-0.30 0.4-0.5

• FOR EXAMPLE IT IS COMMON TO HAVE Pig 1-1.2 1.4 0.5-0.8

SCLERAL OSSICLES WHICH MAY BE BONY Cat 0.09-0.20 0.13-0.60 0.09-0.20 1.1 OR CARTILAGINOUS IN AVIAN AND REPTILE SPECIES. Dog “ “ 0.3-0.4 0.12-0.20 0.6 SCLERAL OSSICLES CORNEA AND SCLERA QUESTIONS? QUIZ WHAT ARE THE EMBRYOLOGIC ORIGINS OF CORNEA AND SCLERA UVEA

• CHOROID • CILIARY BODY • IRIS • FUNCTIONS: SUPPLY NUTRIENTS, REMOVE WASTE, ABSORB LIGHT AND HEAT, PROVIDE FLUID EXIT, CONTROL LIGHT, PROVIDE ACCOMMODATION ETC. • EMBRYOLOGIC ORIGIN: NEUROCREST AND MESODERM AND NEUROECTODERM. CHOROID LAYERS

• SUPRACHOROID • LARGE VESSEL LAYER • MEDIUM VESSEL LAYER • CHORIOCAPILLARIS SUPRACHOROID

• THIS IS AN ELASTIC AND HEAVILY PIGMENTED CONNECTIVE TISSUE THAT ANCHORS THE CHOROID TO THE INNER SCLERA. • IT IS THROUGH THIS AREA THAT AQUEOUS HUMOR PERCOLATES AND EVENTUALLY JOINS CHOROIDAL VESSELS AND SUBSEQUENTLY THE SYSTEMIC CIRCULATION (UVEAL SCLERA OUTFLOW). • THE LAYERS OF MELANOCYTES AND FIBROBLASTS AND COLLAGEN AND ELASTIC FIBERS ARE THOUGHT TO PRODUCE RESISTANCE TO AQUEOUS FLOW THROUGH THIS AREA. LARGE VESSEL LAYER OF THE CHOROID

• THIS LAYER IS IMMEDIATELY INTERNAL TO THE • THE CHOROID ALSO RECEIVES ARTERIAL SUPRACHOROID, AND IS A VASCULAR PLEXUS BLOOD SUPPLY FROM THE LONG THAT CONTAINS MELANOCYTES AND POSTERIOR CILIARY ARTERIES AND THE FIBROCYTES, LARGE VEINS AND ARTERIES. ANTERIOR CILIARY ARTERIES • THE LARGE ARTERIES IN THIS LAYER ARISE • THE CHOROIDAL VEINS DRAIN INTO FOUR FROM THE SHORT POSTERIOR CILIARY (4) PROMINENT VORTEX VEINS. ARTERIES THAT ENTER THE GLOBE NEAR THE OPTIC NERVE AND BRANCH TO SUPPLY THE OPTIC NERVE, RETINA AND THE CHOROID. CHOROID LARGE VESSEL LAYER MEDIUM VESSEL LAYER

• THE MEDIUM-SIZE VESSEL LAYER LIES INTERNAL TO THE LARGE VESSEL LAYER AND WHEN PRESENT THE TAPETUM IS LOCATED IN THIS VASCULAR LAYER. • THERE ARE GENERALLY LARGE AMOUNTS OF MELANOCYTES AND FIBROBLASTS WITHIN THIS LAYER AND CHARACTERISTICALLY A NUMBER OF SMALL ARTERIES AND VEINS AND NERVE FIBERS. • THE NERVE FIBERS ARE PREDOMINANTLY ASSOCIATED WITH THE ARTERIAL SYSTEM AND THEY ARISE FROM THE SHORT CILIARY NERVES AROUND THE OPTIC NERVE. TAPETUM TAPETUM

• May be complete (Cetacean) • Dorsal (most common) • Small islands • Or absent (most birds, some exceptions (Tawny Frogmouths, Great Pooto) • Absent in Beaver, Rhinos, etc. FIBROUS VERSUS CELLULAR TAPETUM

• THIS TREMENDOUS VARIATION IN THE TAPETUM BETWEEN VARIOUS SPECIES INCLUDING FISH, REPTILES, PRIMATES, UNGULATES, AND CARNIVORES. • THE FUNCTION OF THE TAPETUM REMAINS LARGELY UNKNOWN AND ASSUMED TO BE RELATED TO INCREASING THE SENSITIVITY OF THE RETINA IN DIM LIGHT BY REFLECTION. • THE ORIGIN OF THE RODS SEEN IN TAPETAL CELLS IS LIKELY RELATED TO MELANOCYTES AND MELANIN PRODUCTION. CHORIOCAPILLARIS

• THE CHORIOCAPILLARIS IS THE INNERMOST CAPILLARY MEMBRANE OF THE CHOROID AND ITS BASEMENT MEMBRANE FUSES WITH THE BASEMENT MEMBRANE OF THE RETINAL PIGMENT EPITHELIUM (BRUCH'S MEMBRANE). CHORIOCAPILLARIS

• THE CHORIOCAPILLARIS LIKE ALL THE CHOROIDAL VESSELS ARE FENESTRATED AND FUNCTIONS TO PROVIDE A RICH CAPILLARY BED FOR NUTRIENT SUPPLY AND WASTE MANAGEMENT FOR THE RPE AND OUTER RETINAL LAYERS. • BLOOD OCULAR BARRIER HERE IS THE TIGHT JUNCTIONS OF THE RETINAL PIGMENT EPITHELIUM CHOROID REVIEW & QUESTIONS CILIARY BODY

• COMPOSED OF TWO PARTS: PARS PLANA AND PARS PLICATA. • COVERED BY A LAYER OF NON-PIGMENTED AND A LAYER OF PIGMENTED EPITHELIUM. • JUNCTION WITH RETINA IS AT THE ORA SERRATA. • FUNCTION: PRODUCES AQUEOUS HUMOR, PROVIDES ACCOMMODATION AND AN OUTFLOW FOR AQUEOUS. • EMBRYOLOGIC TISSUES OF ORIGIN: NEUROECTODERM, NEUROCREST, AND MESODERM. • CILIARY BLOOD VESSELS ARE FENESTRATED AND THE BLOOD OCULAR BARRIER IS THE TIGHT JUNCTIONS OF THE CILIARY EPITHELIUM. CILIARY BODY (SPECIES VARIATION) CILIARY BODY OF A DOG LIMBUS AND IRIDOCORNEAL ANGLE

• THIS IS AN IMPORTANT REGION OF OCULAR ANATOMY. • JUNCTION OF CILIARY BODY, IRIS, CORNEA, SCLERA AND CONJUNCTIVA. • ANATOMY: PECTINATE LIGAMENTS, UVEAL SCLERAL TRABECULAR MESHWORK, CILIARY CLEFT, CORNEAL SCLERAL TRABECULAR MESHWORK, AQUEOUS COLLECTING VEINS. IRIDOCORNEAL ANGLE

• THE PECTINATE LIGAMENT ANCHORS THE BASE OF THE IRIS TO DESCEMET’S MEMBRANE AND THE CORNEA AND SCLERA. • THE PECTINATE LIGAMENTS CLOSEST TO THE ANTERIOR CHAMBER ARE THICKER AND THEY BECOME PROGRESSIVELY THINNER AS YOU PROGRESS TOWARDS THE CILIARY CLEFT. • THE IRIDOCORNEAL ANGLE IS FURTHER DIVIDED INTO THE UVEAL TRABECULAR MESHWORK AND THE CORNEAL SCLERAL TRABECULAR MESHWORK . IRIDOCORNEAL ANGLE

• THE UVEAL TRABECULAR MESHWORK IS THE MORE INNER PORTION OF THE TRABECULAR MESHWORK LYING CLOSE TO THE BASE OF THE IRIS AND THE CILIARY BODY WHILE THE CORNEAL SCLERAL TRABECULAR MESHWORK IS MORE EXTERNAL LYING JUST UNDER THE SCLERA.

• THE CILIARY CLEFT IS PART OF BOTH OF THESE AND NUMEROUS SYNONYMS ARE PRESENT FOR THE CILIARY CLEFT INCLUDING THE CILIARY SINUS, CILIARY CANAL, CILIARY SCLERAL SINUS ETC.;

• THERE ARE MANY SPECIES VARIATIONS. • FUNCTIONS: PROVIDES A PATHWAY FOR AQUEOUS HUMOR TO EXIT. • EMBRYOLOGIC TISSUES OF ORIGIN: NEUROCREST PREDOMINANTLY, VASCULAR ENDOTHELIUM IS MESODERM. THE ANGLE CHANGES DRAMATICALLY AS A RESULT OF GLAUCOMA (OPEN VS CLOSED) IRIDES

• MOST ANTERIOR PORTION OF THE UVEA. • COMPOSED OF A PUPIL THAT VARIES IN SIZE DUE TO CONTRACTION OF THE DILATOR OR SPHINCTER MUSCLES IN RESPONSE TO LIGHT. • PUPILLARY COLARETTE REPRESENTS THE ANTERIOR EXTENT OF POSTERIOR IRIDAL EPITHELIUM. • EMBRYOLOGIC TISSUES OF ORIGIN: NEUROCREST, AND MESODERM. • BLOOD OCULAR BARRIER HERE IS THE TIGHT JUNCTIONS OF THE IRIDAL VASCULAR ENDOTHELIUM. SPECIES VARIATIONS ARE NUMEROUS REVIEW OF CILIARY BODY, FILTRATION ANGLE, IRIDES LENS

• THE LENS IS A RELATIVELY SIMPLE INTRAOCULAR STRUCTURE THAT IS SUPPORTED BY THE ZONULES. • ANATOMICALLY THE LENS HAS A CAPSULE WHICH IS A BASEMENT MEMBRANE, ANTERIOR LENTICULAR EPITHELIUM, AND THEN LENS FIBERS THAT EXTEND IN A RADIAL PATTERN AROUND AND PAST THE EQUATOR TO THE POSTERIOR PORTION OF THE LENS. • THE CONTINUAL GROWTH OF LENS WILL COMPACT THE NUCLEUS AND LENTICULAR SCLEROSIS DEVELOPS IN ALL LENSES WITH AGE. LENS FUNCTIONS TO ACCOMMODATE

• UNDERSTANDING ACCOMMODATION SPECIES VARIATION IN LENS TO GLOBE RATIO AND SPECIES SHAPE

Samuelson Magrane Anatomy notes/power point ZONULAE

• THE LENS SUSPENSION IS FORMED OF NUMEROUS ZONULAE. • THEY ARE COMPOSED OF SMALL FIBRILS OF NON- COLLAGENOUS GLYCOPROTEIN’S FIBRINOGEN. • ZONULAR FIBRILS ORIGINATE FROM THE CILIARY EPITHELIUM PARTICULARLY IN THE PARS PLICATA REGION (SPECIES VARY CONSIDERABLY). • THESE FIBRILS INTERMIXED WITH THE BASEMENT MEMBRANE OF THE NON-PIGMENTED CILIARY EPITHELIUM AND ALSO WITHIN THE COLLAGEN OF THE LENS CAPSULE. LENS ORIGINATES FROM SURFACE ECTODERM

Samuelson Magrane Anatomy notes/power point LENS GROWTH IS CONTINUAL

Samuelson Magrane Anatomy notes/power point LENS SUTURE LINES

Samuelson Magrane Anatomy notes/power point LENS ULTRASTRUCTURE LENS CHANGES WITH AGE

• WITH CONTINUED GROWTH AND FIBER COMPACTION THE ULTRASTRUCTURE OF THE LENS CHANGES.

Samuelson Magrane Anatomy notes/power point VITREOUS

• VITREOUS HUMOR • •PHYSIOLOGICALLY ‘SLUGGISH’ • •SINGLE LARGEST COMPONENT IN MOST VERTEBRATE EYES • •FEW CELLS PRESENT (HYALOCYTES) • •ALONG WITH AQUEOUS HUMOR MAINTAIN SHAPE OF GLOBE • •GENERALLY GELATINOUS CONSISTENCY • •MAINTAIN RETINAL POSITION AND ATTACHMENT • •SIMPLE ANATOMY: DIVIDED INTO CENTRAL (INTERMEDIATE AND RETROLENTAL) AND PERIPHERAL (CORTEX) REGIONS • •PROVIDE CLEAR MEDIUM FOR TRANSMISSION OF LIGHT • •NORMALLY TRANSPARENT (LOST DURING INFLAMMATION) • •TRANSPARENT JELLY-LIKE • •CLOSE ASSOCIATION WITH THE RETINA ESPECIALLY THE INNER • •99% WATER LIMITING MEMBRANE. •REMAINDER COLLAGEN AND HYALURONIC ACID • • EMBRYOLOGIC ORIGIN PREDOMINANTLY NEUROCREST. • •AVASCULAR • •NOURISHED BY AH VITREOUS DEVELOPMENT AND ANATOMY

Modified from Severin’s Ophthalmology Notes VITREOUS

• PRIMARY VITREOUS: HYALOID ARTERY WHICH REGRESSES INTO CLOQUET’S CANAL AS SECONDARY VITREOUS IS FORMED. • SECONDARY VITREOUS CONSISTS MOSTLY OF WATER, WITH STRANDS OF TYPE II COLLAGEN AND HA. • •TURNOVER OF VITREOUS COLLAGEN IS SLOW TO NON-EXISTENT; GRADUAL LIQUEFACTION AND CONDENSATION OF MANY COLLAGEN FIBERS. • •INFLAMMATION CAN RESULT IN TRACTION BANDS AND RETINAL DETACHMENT VITREOUS

• •HYALOIDEOCAPSULAR LIGAMENT – LENS-VITREOUS CONNECTION • •OPTIC NERVE HEAD ATTACHMENT • •CORTEX (& POSTERIOR HYALOID MEMBRANE) • •OPTIC NERVE HEAD ATTACHMENT • •CORTEX (& POSTERIOR HYALOID MEMBRANE) • HYALOCYTE – RESIDENT CELL • •PHAGOCYTIC (MACROPHAGE?) • •HA PRODUCTION? VITREOUS/ LENS REVIEW QUIZ WHAT EMBRYOLOGIC TISSUES FORM THE PRIMARY VITREOUS? RETINA RETINAL LAYERS

• CLASSICALLY THERE ARE (10) LAYERS DESCRIBED ANATOMICALLY IN RETINAL HISTOLOGY: RPE, INNER AND OUTER SEGMENTS OF THE PHOTORECEPTORS, EXTERNAL LIMITING MEMBRANE, OUTER NUCLEAR, OUTER PLEXIFORM, INNER NUCLEAR, INNER PLEXIFORM, GANGLION CELL, AND NERVE FIBER LAYERS, AND THE INNER LIMITING MEMBRANE. RETINAL PIGMENT EPITHELIUM

• FORMS THE BLOOD OCULAR BARRIER FOR THE CHOROID. • FUNCTIONS: PROVIDE METABOLIC NEEDS OF THE PHOTORECEPTORS. • EMBRYOLOGIC TISSUE OF ORIGIN IS NEUROECTODERM. RPE SURFACE IS TEXTURED WITH MANY PROCESSES THAT SURROUND THE OUTER SEGMENTS OF THE PHOTORECEPTORS RETINAL PIGMENT EPITHELIUM

• THE RETINAL PIGMENT EPITHELIUM PHAGOCYTIZE APPROXIMATELY 1/4 OF THE RODS AND CONE DISCS. • THE RETINAL PIGMENT EPITHELIUM JOINS THE PIGMENTED CILIARY EPITHELIUM AT THE ORA SERRATA. • THE NUCLEI OF THE RETINAL PIGMENT EPITHELIUM ARE ROUND AND THE CYTOPLASM IS FILLED WITH SMOOTH ENDOPLASMIC RETICULUM, MITOCHONDRIA, AND MYELIN LIKE GRANULES EXCEPT WHERE THESE CELLS OVERLIE THE TAPETUM AND THERE THEY ARE RELATIVELY DEVOID OF PIGMENT. • THE RETINAL PIGMENT GRANULES ARE ELONGATED AND LANCET-LIKE IN SHAPE INTERPHOTORECEPTOR RPE MATRIX

• NUTRIENT AND WASTE TRANSFER. • PHAGOCYTOSIS OF ROD AND CONE OUTER SEGMENTS. • NUTRIENT TRANSFER TO THE END PROCESSES OF THE MUELLER CELLS (EXTERNAL LIMITING MEMBRANE).

Samuelson Magrane Anatomy notes/power point PHOTORECEPTORS

The rod and cone outer segments are connected to the inner segments by a cilium, whose basal body is in the outer portion of the inner segment. This outer portion of the inner segment also contains many mitochondria and this region is often called an ellipsoid. RODS AND CONES

Samuelson Magrane Anatomy notes/power point OUTER NUCLEAR LAYER

Samuelson Magrane Anatomy notes/power point INNER NUCLEAR LAYER

Samuelson Magrane Anatomy notes/power point INNER NUCLEAR LAYER

Samuelson Magrane Anatomy notes/power point INNER NUCLEAR LAYER

Samuelson Magrane Anatomy notes/power point INNER NUCLEAR LAYER

Samuelson Magrane Anatomy notes/power point INNER PLEXIFORM AND GANGLION CELL LAYERS

Samuelson Magrane Anatomy notes/power point NERVE FIBER AND OPTIC NERVE

Samuelson Magrane Anatomy notes/power point OPTIC NERVE

Samuelson Magrane Anatomy notes/power point RETINA AND OPTIC NERVE QUESTIONS QUIZ WHAT ARE THE BLOOD OCULAR BARRIERS IN THE GLOBE? CENTRAL VISUAL PATHWAYS AND OTHER CRANIAL NERVES

Modified from Grahn/Spiess, EBook, Ocular Disorders of Companion Animals (Diagnosis, Medical and Surgical Therapies