RCSI Orbit, Eyeball and Lacrimal Apparatus Year 2 Semester 1 PDF

RCSI Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in Éirinn Orbit, eyeball and lacrimal apparatus Class Year 2 Semester 1 Course Medicine Lecturer Dr. Vijayalakshmi S B Date 14/11/2024 LEARNING OUTCOMES 1. Identify the bones of the orbit and its boundaries 2....

RCSI Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in Éirinn Orbit, eyeball and lacrimal apparatus Class Year 2 Semester 1 Course Medicine Lecturer Dr. Vijayalakshmi S B Date 14/11/2024 LEARNING OUTCOMES 1. Identify the bones of the orbit and its boundaries 2. Describe the Anatomy of the eyelids, conjunctiva, and lacrimal gland. Explain the importance of maintenance of corneal integrity 3. Identify the superior and inferior orbital fissures and their contents 4. Describe the extraocular muscles of the eyeball 5. Explain the role of cranial nerves III, IV, VI and discuss lesions to them and their testing 6. Describe the structure of the eyeball and the retina BONES OF THE ORBIT  ORBIT - BOUNDARIES Superior wall (Roof) – orbital part of the frontal bone, lesser wing of the sphenoid Inferior wall (Floor) – zygomatic process of the maxilla, zygomatic bone Medial wall – frontal process of the maxilla, lacrimal, ethmoid, and frontal bones Lateral wall – zygomatic bone, frontal process of the zygomatic bone, and the zygomatic process of the frontal bone Apex – Optic canal in the lesser wing of the sphenoid  FISSURES AND FORAMINA Sphenoid bone surrounds all important structures that enter and leave orbit  SUPERIOR ORBITAL INFERIOR ORBITAL FISSURE FISSURE (FINALIST) (ZOI3) Zygomatic Nerve Frontal Nerve Orbital branches of Inferior & superior division of pterygopalatine ganglion oculomotor nerve Inferior division of the Nasociliary Nerve inferior ophthalmic vein Abducens Nerve Infraorbital vessels (A+V) Lacrimal Nerve Infraorbital nerve Inferior Ophthalmic Vein OPTIC CANAL Superior Ophthalmic vein Trochlear Nerve Optic nerve (CN II) Ophthalmic artery INFRAORBITAL FORAMEN Infra-orbital nerve and vessels SURFACE ANATOMY OF EYELIDS  Tarsal plate EYELIDS Superior + Inferior Tarsus Superior Tarsus has Levator palpebrae superioris (LPS) muscle, which raises/opens the eyelid (CN III/ Oculomotor nerve) Behind each eyelid is a membrane called “Conjunctiva” - when inflamed, it’s called Conjunctivitis They also have tarsal glands: Lipid secretion, which increases the viscosities of the tears and prevents evaporation – when inflamed, it’s called a Chalazion/Meibomian cyst Eyelashes Sebaceous glands + sweat glands – when inflamed, they are known as “Stye/Hordeolum”  OPENING AND CLOSING OF EYELIDS Oculomotor nerve (CNIII) Zygomatic/Temporal branch of CN VII Sympathetic innervation  PTOSIS Loss of function of either the LPS muscle or superior tarsal muscle results in drooping of the eyelid  LACRIMAL APPARATUS Consists of the following: Lacrimal glands Lacrimal ducts Lacrimal canaliculi Lacrimal sac Nasolacrimal duct Lacrimal gland: Exocrine gland on the top outside corner of each orbit Secretes lacrimal fluid 8-12 lacrimal (excretory) ducts – convey fluid from the glands to the conjunctival sac Eyelids come together from lateral to medial, so drainage is lateral to medial.  LACRIMAL APPARATUS Tears drain: Lacrimal gland & its ducts via the Puncta into each lacrimal canaliculi into the lacrimal sac and out into the nasolacrimal ducts The nasolacrimal ducts then empty into the inferior nasal meatus Infection or blockage of the Nasolacrimal system = Epiphora, which means the overflow of tears Infection of the Lacrimal gland itself is called Dacryoadenitis Treatment of both depends on the cause  INNERVATION OF THE LACRIMAL GLAND Production of lacrimal fluid is stimulated by parasympathetic impulses from CN VII (Facial nerve) Facial nerve Palsy? SENSORY NERVE AND BLOOD SUPPLY EYEBALL EYEBALL CILIARY BODY Lens shape + aqueous humor production Smooth muscle is innervated by parasympathetic fibres only originating in CN III and reaching the ciliary muscle via the short ciliary nerve – role in Accommodation Reflex  GLAUCOMA Aqueous humour Made by cells that line the ciliary body Constant production Drains out through trabecular meshwork. Supplies nutrients to the avascular cornea and lens Maintains intra-ocular pressure Glaucoma Partial blockage within the trabecular meshwork. Restricts the drainage of aqueous humour Increased pressure = damage to Optic nerve  GLAUCOMA Increased pressure = damage to Optic nerve  RETINA Two Layers: 1. Pigment layer - attached to choroid 2. Neural layer - attached to the pigment layer at the optic nerve and ora serrata (junction between the retina and ciliary body) Optic Disc (OD) Where the optic nerve leaves the retina Central retinal artery radiates from OD No light-receptors = blind spot Macula Lutea Central depression = fovea centralis Greatest photoreceptor sensitivity Cones > Rods in macula lutea  OPTIC NERVE Conveys visual impulses from the retina to the brain Covered in all layers of meninges Central retina artery and vein within meninges Nasal fibres (Temporal Field of vision) decussate at the optic chiasma Optic tract synapses in lateral geniculate body Axons pass to the visual cortex as optic radiation Some axons from optic tracts enter the midbrain Pupillary light reflex Lens accommodation Conjugate  CLINICAL ASPECTS Retinal detachment Diabetic Retinopathy  CLINICAL ASPECTS Hyphema – blood in the Cataracts – clouding of anterior chamber the lens by protein clumping Cavernous sinus thrombosis  EXTRAOCULAR (EXTRINSIC) MUSCLES Muscle that moves the eye All supplied by CN III, IV and VI 6 Muscles 4 Rectus Superior, inferior, medial, lateral 2 Oblique Superior, inferior Squint = Strabismus Asymmetry of movement  INTRINSIC MUSCLES Located within the eyeball, which controls the shape of the lens and size of the pupil Innervated by autonomic nerve fibres Muscles include Ciliary muscle – responsible for the accommodation of the lens of the eye for near vision Sphincter pupillae – responsible for pupillary constriction Dilator pupillae – responsible for pupillary dilatation EXTRAOCULAR (EXTRINSIC) MUSCLES  MOTOR NERVE SUPPLY = (LR6 SO4)3 Abducent (CN VI) Lateral Rectus Trochlear (CN IV ) Superior oblique Oculomotor (CN III) Superior rectus Inferior rectus Medial rectus Inferior oblique LR6SO4 NERVES SUPPLYING INTRINSIC MUSCLES - CILIARY GANGLION Parasympathetic = sphincter pupillae and ciliary muscle Sympathetic = Dilator Pupillae  BLOOD SUPPLY & VENOUS DRAINAGE AXIS OF EYE  ACTION OF MUSCLES FROM CENTRAL GAZE POSITION Medial Rectus = Adduct Lateral rectus = Abduct Superior Rectus = Up and in Inferior Rectus = Down and in Superior Oblique = Down and out Inferior Oblique = Up and out MEDIAL AND LATERAL RECTUS  CLINICAL EXAMINATION OF THE EYE Need to isolate the action of each muscle For the superior and inferior rectus, you abduct the eye first  CLINICAL EXAMINATION OF THE EYE For superior and inferior obliques, you first adduct the eye  Action RIGHT eye Lateral Medial - Nose Clinical Examination Abduct 1st Adduct 1st  STRABISMUS Why? Poor vision in one eye commonest Eye physically stuck Post-traumatic Muscle weakness CN palsy PUPILLARY LIGHT REFLEX  SDL Horner’s syndrome Cavernous sinus thrombosis Cataract PRACTICE QUESTIONS REFERENCES