Download Ocular Anatomy

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