OCULAR ANATOMY and • the Middle Coats of the Eye • the Internal Ocular Media DISSECTION • the Retina Structures External to the Eye JEFFREY M

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The eye is a 23 mm organ...how difficult can this be?

• The orbit • The outer coats of the eye OCULAR ANATOMY AND • The middle coats of the eye • The internal ocular media DISSECTION • The retina Structures external to the eye JEFFREY M. GAMBLE, OD • COLUMBIA EYE CONSULTANTS OPTOMETRY • The lacrimal apparatus & • The extraocular muscles UNIVERSITY OF MISSOURI DEPARTMENT OF OPHTHALMOLOGY • The orbital blood vessels CLINICAL INSTRUCTOR • The nerve supply of the orbit

The Orbit The Orbit • Openings in the orbit –Superior orbital fissure • Bones of the orbit • Oculomotor nerve –The maxillary • Trochlear nerve • Trigeminal nerve The palatine – • Various sympathetic nerves –The frontal • Superior ophthalmic vein –Inferior orbital fissure –The sphenoid • Infraorbital nerve –The zygomatic • Zygomatic nerve –The ethmoid • Infraorbital artery –Ethmoidal foramen The lacrimal – • Connects orbit and ethmoid sinus –Optic canal • Optic nerve • Ophthalmic artery

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The Outer Coats The Middle Coats

• The Sclera (the white of the eye) • The Uvea - Purpose is to supply blood and drain blood. Also pigmented –Episcleral layer to reduce stray light –Stromal layer The Choroid –Lamina fusca – • The Cornea • Vascular supply of the eye –Epithelium - six layers thick attached to a basement membrane • Acts like the radiator of the eye –Bowman’s membrane - any injury that breaks through this layer will scar –The Ciliary Body –Stroma - makes up 90% of the corneal thickness. • Makes the aqueous humor and has some role in accommodation –Descemet’s membrane - elastic membrane attaches to the endothelium –Endothelium - works like a pump to keep the cornea the appropriate thickness –The Iris • The Limbus • Primary role is to adjust the amount of light entering the eye –The junction of the cornea and sclera

Internal Ocular Media The Retina • 2 Functions: • Anterior and posterior chambers –Detect light and movement through the rods – Anterior segment: in front of the lens –Transmit color vision and form through the cones Posterior segment: behind the lens – • Multiple layers • The crystalline lens - works like the zoom of a camera –Pigment epithelial layer – Receives nutrients from aqueous humor –Photoreceptors – With age, the lens yellows, hardens, loses elasticity and the ciliary muscle –External limiting membrane weakens = presbyopia –Outer nuclear layer • The aqueous humor –Outer plexiform layer – Fills the anterior segment –Inner nuclear layer – Nourishes the cornea and lens (both are avascular) –Inner plexiform layer • The vitreous humor –Ganglion cell layer – Fills the posterior segment –Nerve fiber layer – Attached at the ora serrata of the retina and the optic disc –Internal limiting membrane

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The Retina The Retina

• The Fovea • Photoreceptors –The most sensitive portion of the retina –Responsible for the conversion of light signals into electricity –Contains only cones –The signal is then conducted by the optic nerve to the brain –Long and thin cells with an outer and inner segment –Accounts for a “dime-sized” area of vision at arms length –Outer segment contains disc lamellae (camera film) • The Retinal Pigmented Epithelium (RPE) • Rods –Restricts material from the choroid entering the eye (blood-retina) –Rods respond to monochromatic light and compile small pieces of information barrier over a large area –Very sensitive to movement –Reduces stray light to protect photoreceptors –120 million in the eye Provide photorecepters with nourishment – • Cones –Digest spent photoreceptor lamellae discs –Respond to only wavelengths of light in the color spectrum –Reservoirs for Vitamin A (eat your carrots) –Located primarily in the fovea –6.5 million in the eye

Structures External The Lacrimal Apparatus to the Eye • Eyebrow –Primary role is protection of the eye • The Lacrimal Gland –Functions to keep sweat out of the eye –Innervated by both sympathetic and parasympathetic system –Can serve to limit opportunities for a mate (unless you’re making 40 million as an NBA 10-12 openings into the eye star) – –Reflex tearing will accompany irritation to the cornea (dryness), coughing, sneezing, taste or smell. • Eyelids –Protect the eye • Tear Film –Limit light –3 Layers –Spread the tear film over the eye and push tears out the punctum • Lipid (secreted by the meibomian glands) • Aqueous (secreted by the lacrimal gland) • Conjunctiva - Tarsal and Bulbar –Thin layer of epithelium that covers the globe and inner lids • Mucous (secreted by conjunctival goblet cells) –Turns from the lid back to the globe at the conjunctival fornix (“no that bug that flew in –All three layers contain Lysozyme, a natural bacteriocidal your eye cannot lay eggs behind your eye”)

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The Extraocular Muscles Orbital Blood Vessels • Superior Rectus - 1) Elevates 2) adducts 3) intorts • Inferior Rectus - 1) Depresses 2) adducts 3) extorts • The internal carotid branches into the ophthalmic artery and then separates into the • Medial Rectus - 1) Adducts following branches: • Lateral Rectus - 1) Abducts –Central retinal artery • Superior Oblique - 1) Intorts 2) Depresses 3) Abducts –Short posterior ciliary arteries Inferior Oblique - 1) Extorts 2) Elevates 3) Abducts • –Long posterior ciliaries • Levator - Raises the upper lid. –Anterior ciliary arteries –Lacrimal artery –Muscular branches –Supraorbital artery –Posterior ethmoidal artery –Anterior ethmoidal artery –Medial palpebral arteries –Nasal artery –Supratrochlear artery

Ocular Nerves 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

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