Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Contact lens wikipedia , lookup
Blast-related ocular trauma wikipedia , lookup
Keratoconus wikipedia , lookup
Mitochondrial optic neuropathies wikipedia , lookup
Idiopathic intracranial hypertension wikipedia , lookup
Diabetic retinopathy wikipedia , lookup
Visual impairment due to intracranial pressure wikipedia , lookup
Cataract surgery wikipedia , lookup
Photoreceptor cell wikipedia , lookup
Eyeglass prescription wikipedia , lookup
9/25/2014 The eye is a 23 mm organ...how difficult can this be? OCULAR ANATOMY AND DISSECTION JEFFREY M. GAMBLE, OD COLUMBIA EYE CONSULTANTS OPTOMETRY & UNIVERSITY OF MISSOURI DEPARTMENT OF OPHTHALMOLOGY CLINICAL INSTRUCTOR The Orbit • The orbit • The outer coats of the eye • The middle coats of the eye • The internal ocular media • The retina • Structures external to the eye • The lacrimal apparatus • The extraocular muscles • The orbital blood vessels • The nerve supply of the orbit The Orbit • Openings in the orbit • Bones of the orbit – The maxillary – The palatine – The frontal – The sphenoid – The zygomatic – The ethmoid – The lacrimal – Superior orbital fissure • Oculomotor nerve • Trochlear nerve • Trigeminal nerve • Various sympathetic nerves • Superior ophthalmic vein – Inferior orbital fissure • Infraorbital nerve • Zygomatic nerve • Infraorbital artery – Ethmoidal foramen • Connects orbit and ethmoid sinus – Optic canal • Optic nerve • Ophthalmic artery 1 9/25/2014 The Outer Coats • The Sclera (the white of the eye) – Episcleral layer – Stromal layer – Lamina fusca • The Cornea – Epithelium - six layers thick attached to a basement membrane – Bowman’s membrane - any injury that breaks through this layer will scar – Stroma - makes up 90% of the corneal thickness. – Descemet’s membrane - elastic membrane attaches to the endothelium – Endothelium - works like a pump to keep the cornea the appropriate thickness • The Limbus The Middle Coats • The Uvea – The Choroid Purpose is to supply blood and drain blood. Also pigmented to reduce stray light • Vascular supply of the eye • Acts like the radiator of the eye – The Ciliary Body • Makes the aqueous humor and has some role in accommodation – The Iris • Primary role is to adjust the amount of light entering the eye – The junction of the cornea and sclera Internal Ocular Media • Anterior and posterior chambers – Anterior segment: in front of the lens – Posterior segment: behind the lens • The crystalline lens - works like the zoom of a camera – Receives nutrients from aqueous humor – With age, the lens yellows, hardens, loses elasticity and the ciliary muscle weakens = presbyopia • The aqueous humor – Fills the anterior segment – Nourishes the cornea and lens (both are avascular) • The vitreous humor – Fills the posterior segment – Attached at the ora serrata of the retina and the optic disc The Retina • 2 Functions: – Detect light and movement through the rods – Transmit color vision and form through the cones • Multiple layers – Pigment epithelial layer – Photoreceptors – External limiting membrane – Outer nuclear layer – Outer plexiform layer – Inner nuclear layer – Inner plexiform layer – Ganglion cell layer – Nerve fiber layer – Internal limiting membrane 2 9/25/2014 The Retina • The Fovea – The most sensitive portion of the retina – Contains only cones – Accounts for a “dime-sized” area of vision at arms length • The Retinal Pigmented Epithelium (RPE) – Restricts material from the choroid entering the eye (blood-retina) barrier – Reduces stray light to protect photoreceptors – Provide photorecepters with nourishment – Digest spent photoreceptor lamellae discs – Reservoirs for Vitamin A (eat your carrots) Structures External to the Eye • Eyebrow – Primary role is protection of the eye – Functions to keep sweat out of the eye – Can serve to limit opportunities for a mate (unless you’re making 40 million as an NBA star) • Eyelids – Protect the eye – Limit light – Spread the tear film over the eye and push tears out the punctum • Conjunctiva - Tarsal and Bulbar – Thin layer of epithelium that covers the globe and inner lids – Turns from the lid back to the globe at the conjunctival fornix (“no that bug that flew in your eye cannot lay eggs behind your eye”) The Retina • Photoreceptors – Responsible for the conversion of light signals into electricity – The signal is then conducted by the optic nerve to the brain – Long and thin cells with an outer and inner segment – Outer segment contains disc lamellae (camera film) • Rods – Rods respond to monochromatic light and compile small pieces of information over a large area – Very sensitive to movement – 120 million in the eye • Cones – Respond to only wavelengths of light in the color spectrum – Located primarily in the fovea – 6.5 million in the eye The Lacrimal Apparatus • The Lacrimal Gland – Innervated by both sympathetic and parasympathetic system – 10-12 openings into the eye – Reflex tearing will accompany irritation to the cornea (dryness), coughing, sneezing, taste or smell. • Tear Film – 3 Layers • Lipid (secreted by the meibomian glands) • Aqueous (secreted by the lacrimal gland) • Mucous (secreted by conjunctival goblet cells) – All three layers contain Lysozyme, a natural bacteriocidal 3 9/25/2014 The Extraocular Muscles • Superior Rectus - 1) Elevates 2) adducts 3) intorts • Inferior Rectus - 1) Depresses 2) adducts 3) extorts • Medial Rectus - 1) Adducts • Lateral Rectus - 1) Abducts • Superior Oblique - 1) Intorts 2) Depresses 3) Abducts • Inferior Oblique - 1) Extorts 2) Elevates 3) Abducts • Levator - Raises the upper lid. Ocular Nerves • • • • • • Orbital Blood Vessels • The internal carotid branches into the ophthalmic artery and then separates into the following branches: – Central retinal artery – Short posterior ciliary arteries – Long posterior ciliaries – Anterior ciliary arteries – Lacrimal artery – Muscular branches – Supraorbital artery – Posterior ethmoidal artery – Anterior ethmoidal artery – Medial palpebral arteries – Nasal artery – Supratrochlear artery Cow Eye Dissection Optic Nerve (II) - Carries vision to the brain Oculomotor Nerve (III) - Innervates the superior rectus, levator, inferior rectus, inferior oblique and finally the iris Trochlear Nerve (IV) - Innervates the superior oblique Trigeminal Nerve (V) - Sensory innervation to cornea Abducens Nerve (VI) - Innervates the lateral rectus Facial Nerve (VII) - Closes the upper lid 4 9/25/2014 5 9/25/2014 6 9/25/2014 • [email protected] 26 7