Download of EYE

Ocular Anatomy Intermediate (for ABO)
or
Ocular Anatomy & Physiology (for AOA)
Learning Objectives:
1. Correctly identify ocular structures around or within
the eye
2. List the key functions of various ocular structures
3. Accurately point out key external landmarks on, or
around the eye
4. Name major bones of the orbit that surround the
eye
5. List the six extraocular muscles that control eye
movement
Lecturer:
M. Patrick COLEMAN, ABOC, COT
Kerrville, TX
Topics to be covered:
6. Accurately identify key ocular structures that
compose the visual pathway
Let’s get oriented first…
• 3 Major Layers (Tunics) of the
Eye
• Superior = UPWARD (or TOP)
• Ocular Media
• Inferior = DOWNWARD (or BOTTOM)
• Ocular Adnexa
• Nasal / Medial = TOWARD NOSE
• The Bony Orbit
• Temporal / Lateral = TOWARD TEMPLE
• Extraocular Muscles (EOMs)
• Visual Pathway
• Posterior = BEHIND (or Toward the BACK)
• Anterior = IN FRONT (or Toward the Front)
FIBROUS TUNIC
3 Major Layers (Tunics) of EYE
• FIBROUS TUNIC
• UVEAL TRACT or (Vascular Tunic)
• Protective
layer of eye
• Tough &
fibrous
• Two parts:
– Cornea
• NERVOUS TUNIC
– Sclera
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Fibrous Tunic: Cornea
Fibrous Tunic (cont.): Layers of the Cornea
• Anterior 1/6th of the fibrous tunic
• Clear; Avascular; approx. +40.00D power
• 5 layers: Just remember ABCs…
•
Epithelium (“A”pithelium?)
•
Bowman's Membrane
•
Stroma (“C”troma? Like ceiling…)
» Dua’s Layer (Sixth layer? Reported in May
2013)
• Descemets Membrane
• Endothelium
Fibrous Tunic (cont.): Sclera
• White in color (appears bluish in infants)
• Avascular (without blood vessels; (what look
like blood vessels in the sclera are really in
the EPISCLERA which lays on top of the
sclera)
• Makes up posterior 5/6th of fibrous tunic
• Very tough!
UVEAL TRACT (Vascular Tunic)
• IRIS (colored part of eye)
• CILIARY BODY (behind iris)
• CHOROID (can see it on retinal photos,
and OCT scans of the retina!)
• Cornea & sclera are the “same” material!
UVEAL TRACT (cont.):
Iris, Ciliary Body, Choroid…
UVEAL TRACT (cont.): IRIS
• Color of iris dependent on
amount of pigment
– Very little pigment = BLUE
EYE
– Medium amount of pigment =
HAZEL EYE
– Heavy amount of pigment =
BROWN EYE
• “Hole” in center of iris regulates
amount of light entering the
eye…what’s it called?
• Dilator muscles vs. Sphincter
muscles
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UVEAL TRACT (cont.): Ciliary Body
• Located just behind the iris, at its base
UVEAL TRACT (cont.): Ciliary Body
• Ciliary Processes produces aqueous humor
constantly (keeps our eye ‘filled’ with fluid so it
remains “inflated”)
• Ciliary Muscles control the focusing of the lens
– When the ciliary muscles RELAX, they pull the
zonules tight, making the lens thinner, so we
can see FAR clearly.
– When the ciliary muscles CONTRACT, they
release the tension on the zonules so the lens
can grow thicker, (causing us to focus, or
accommodate); this allows us to see clearly at
NEAR distances.
The CILIARY BODY
(processes & muscles)
UVEAL TRACT (cont.): CHOROID
• Supplies blood to the iris,
ciliary body, inner retina &
inner sclera
• The “CHOW HALL” of the
eye - brings nourishment
& oxygen
– “Sandwiched” between the
SCLERA and the RETINA
UVEAL TRACT (cont.): CHOROID
NERVOUS TUNIC
The Retina…that’s it!
• Retina ‘lines’ the back 2/3rds of eye
• 10 layers thick; all the layers are transparent except
the RPE (retinal pigment epithelial) layer
• Retina lies on top of the choroid
• It’s in contact with the vitreous humor (fluid)
• Contains cells that respond to light (photoreceptors);
two (2) types – CONES & RODS
• It is a NEURAL CONNECTION TO THE BRAIN; often
considered an extension of the brain! (It’s directly
connected to the II CN, which is the Optic Nerve.)
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Nervous Tunic (i.e., the RETINA)
Nervous Tunic (i.e. RETINA) cont.
• ‘Sandwiched’ between the VITREOUS & CHOROID
• Retina has 10 layers; key layers?
• Nerve Fiber Layer (NFL)
• Photoreceptor (Rods & Cones)
• Retinal Pigment Epithelium (RPE)
Nervous Tunic: The Retina (cont.)
Nervous Tunic (i.e. RETINA) cont.
• The photoreceptor layer contains RODS & CONES
• Rods & Cones convert light to an electro-chemical
impulse, which gets passed along the ganglion
cells, to the nerve fiber layer (NFL)
– Then it goes to the brain via the Optic Nerve (II CN)
• Rods & Cones only “sense” wavelengths in the visible
electromagnetic spectrum (ROY G. BIV) which is
between: 390nm (VIOLET) to 750nm (RED).
Nervous Tunic (i.e. RETINA) cont.
• CONES are for bright (photopic)
conditions; can see color & fine
detail
– There are approximately 6
million cones in the retina
– The fovea centralis (center of
Macula) contains ONLY
CONES!
– Cones emit a chemical called
IODOPSIN
Trivia Question:
• What percentage of MEN are
“colorblind”?
• What percentage of WOMEN
are “colorblind”?
Nervous Tunic (i.e. RETINA) cont.
• RODS are for dim
(scotopic) conditions;
They provide a poor
image but have a great
ability to sense
movement
– There are
approximately 120
million rods in the
retina.
– Rods emit a chemical
called RHODOPSIN
TRIVIA QUESTION:
* When entering a dark
movie theater, whose eyes
will ‘dark adapt” the
quickest: A young person
or an elderly person?
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Nervous Tunic (i.e. RETINA) cont.
• The retina is CLEAR, with the
exception of the Retinal Pigment
Epithelium (RPE) layer which, like
the iris, contains pigment
– The RPE layer is the “garbage
man”:
• It absorbs excess light
–AND
• It must remove the chemicals
emitted by the rods
(rhodopsin) and cones
(iodopsin) as these chemicals
are TOXIC TO THE RETINA.
Nervous Tunic (i.e. RETINA) cont.
• The layer closest to the
vitreous humor is the
RETINAL NERVE
FIBER LAYER (NFL)
• This layer contains the
nerves coming from
every part of the retina
• At the optic nerve, the
nerve fiber bundles are
most concentrated
superiorly & inferiorly
• Ever do an OCT scan of
the area around the optic
nerve head (ONH) of a
glaucoma patient?
Why?
Nervous Tunic (i.e. RETINA) cont.
Zeiss OCT scan
of optic nerve
head (ONH) of
both eyes:
Green = GOOD
Yellow =
BORDERLINE
Red = BAD
(glaucoma?!)
Nervous Tunic (i.e. RETINA) cont.
• 9/10ths of the
Retinal blood
supply comes
from the
CENTRAL
RETINAL
ARTERY (CRA)
• As the nerve fibers
approach the optic
disk, they start to
bundle closer
together and form
the cable to the brain
we call the OPTIC
NERVE (II CN)
• In GLAUCOMA, these
nerve fibers die off
So that’s it, right? HARDLY!
• The TUNICS of the eye are
just “layers” of the main
functional components.
• There are many other “parts”
that make up the eye and help
it work correctly.
• Time to look at the “rest of the
eye”…
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OCULAR MEDIA
• These are the clear
structures of the eye
light must pass
through to get to the
retina.
• They are the:
– CORNEA
– AQUEOUS HUMOR
– LENS
– VITREOUS HUMOR
OCULAR MEDIA
(cont.):
TEAR FILM
OCULAR MEDIA - Cornea (cont.)
• Cornea
– Needs a good tear layer to transmit light well
– Good quality tears have three parts:
• Lipid (oil) layer (top/outermost layer) keeps aqueous layer from evaporating away
too quickly
• Aqueous layer (middle layer) - water portion
of tear (thickest layer!)
• Mucin (mucous) layer (innermost/against
cornea) - keeps tears ‘stuck’ against cornea
OCULAR MEDIA – Aqueous Humor (cont.)
• AQUEOUS HUMOR
– Produced by the CILIARY BODY in “posterior
chamber” of the eye’
– Flows thru the pupil into “anterior chamber”
– Provides nourishment to Endothelial layer of
the cornea & maintains “pressure” in the eye
– Drains thru the TRABECULAR MESHWORK
and into the CANAL OF SCHLEMM,
dissipating into the layers of the sclera
OCULAR MEDIA – Aqueous Humor (cont.)
OCULAR MEDIA – Lens (cont.)
• Lens (sometimes called the “Crystalline Lens”)
– Three parts:
• CAPSULE
• CORTEX
• NUCLEUS
– Changes shape to focus images on retina
– Soft & flexible in the young; harder as we age
– Cataracts form in this structure (BUMMER!)
– Approximately +18.00D to +21.00D of power
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OCULAR MEDIA – Lens (cont.)
OCULAR MEDIA – Vitreous (cont.)
• VITREOUS HUMOR
– Fills the posterior 5/6ths of the eye
– When we are young, it is thick and “jello-like”
– As we age, it breaks down and becomes more
watery. It also tends to ‘shrink’ a bit causing PVDs
(post-vitreous detachments)
– When we see “floaters” it is usually debris in the
vitreous that’s moving around
– What you have is all you get. If you lose vitreous,
the body will NOT make more!
OCULAR MEDIA - Vitreous (cont.)
So is that it? As they say on TV,
“But wait! There’s More!!!”
• Ocular Adnexa
• The Bony Orbit
• Extraocular
Muscles (EOMs)
OCULAR ADNEXA
• Eyelids &
Landmarks
• Muscles of the
eyelids
• Tarsal Plate &
Glands
• Conjunctiva &
Lacrimal System
EYELIDS & LANDMARKS
• Eyelids are the folds of tissue that cover the
eye itself. Their primary purpose is…
– PROTECTION!!!
– Limit amount of light entering the eye (giving
the pupil a nice assist at times)
– Keep dust & dirt out of the eye (& fingers &
racquetballs & fish hooks and…well, you get
the idea!)
– Eyelashes = ‘early warning’ sensors
• (Which lid has MORE lashes? UPPER or lower?)
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LANDMARKS of the EYELIDS
EYELIDS & LANDMARKS (cont.)
• MUSCLES of the EYELIDS
– Muscles open & close the lids (duh!)
– To OPEN the lids, we use the:
• LEVATOR PALPEBRAE SUPERIORIS (let’s
just go with “LEVATOR”!) and the
• MUSCLE OF MUELLER
– The III CN (Oculomotor nerve) “operates” these
nerves
– Which muscle is the PRIMARY worker here?
LEVATOR PALPEBRAE
SUPERIORIS (LEVATOR)!
• A way to remember?
• Mueller gets on the LEVATOR to go UP &
fix the oculoMOTOR on the 3rd (III) floor
• Levator OPENS the eyelids
– Mueller helps
– III CN (Oculomotor nerve) controls them both
ORBICULARIS OCULI
EYELIDS & LANDMARKS (cont.)
• MUSCLES of the EYELIDS (cont.):
– To CLOSE the lids, we use the:
• ORBICULARIS OCULI muscle and the…
• RIOLAN’S muscle
– The VII CN (Facial nerve) “operates” these
two muscles
QUESTION:
Which is the “PRIMARY” muscle for closing
the lids?
EYELIDS & LANDMARKS (cont.)
• It is the primary muscle for closing the eyelid
Just remember:
Orbicularis Oculi CLOSES the eye!
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EYELIDS & LANDMARKS (cont.)
TARSAL PLATE IN THE LID
• TARSAL PLATE:
– Levator & Mueller’s muscle attach to this
– It is considered the “skeleton” of the lid as it’s
made up of tough, fibrous tissue
– When the doctor “everts” the lid to look for a
foreign body (FB) or wayward contact, they are
pushing at the top of the TARSAL PLATE to get
the lid to flip inside out
OCULAR ADNEXA (cont.) - GLANDS
OCULAR ADNEXA (cont.) - Glands
• GLANDS
– The adnexa (eyelids & surrounding
structures) contain GLANDS that
secrete OIL or AQUEOUS
• SEBACEOUS GLANDS secrete
OIL
• LACRIMAL GLANDS secrete
AQUEOUS
OCULAR ADNEXA (cont.) - Conjunctiva
OCULAR ADNEXA (cont.) - Conjunctiva
• CONJUNCTIVA
– Thin, saran-wrap-like layer on the surface of
your sclera and inner eye lids
• TWO PARTS: PALPEBRAL & BULBAR
• Where the two parts meet is called the
FORNIX
– Protection; barrier to infection; keeps things
from getting ‘behind’ the eye
– Contains GOBLET CELLS that secrete MUCIN
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OCULAR ADNEXA (cont.)-Lacrimal System
• LACRIMAL SYSTEM
– These are all the structures involved in the
production, distribution, & disposal of tears
OCULAR ADNEXA (cont.)
LACRIMAL SYSTEM:
– SEVEN (7) distinct structures:
• 1) Lacrimal Gland
• 2) Lacrimal Canal (Ducts)
• 3) Conjunctival Sac
• 4) Puncta (upper and lower)
• 5) Canaliculi
• 6) Lacrimal Sac
• 7) NasoLacrimal Duct
THE BONY ORBIT
• Additus Orbitae (the opening of the bony orbit)
THE BONY ORBIT (cont.)
• The bony orbit is composed of seven (7) bones that
surround the eye to protect it & provide passage or
attachment points for various structures (like the eye
muscles, nerves, fat, lacrimal gland and vascular
supply)
• Bony orbit is comprised of a:
– ROOF (lesser wing of SPHENOID & FRONTAL)
– FLOOR (MAXILLA, PALATINE, & ZYGOMATIC)
– LATERAL WALL (ZYGOMATIC & greater wing of
SPHENOID)
– MEDIAL WALL (MAXILLA, ETHMOID,
LACRIMAL & lesser wing of SPHENOID)
THE BONY ORBIT (cont.)
• ROOF: (Light Shines From
the roof)
– Lesser wing of Sphenoid
(foramina for optic nerve [II
CN] to pass through!)
– Frontal bone (fossa for
lacrimal gland)
• FLOOR: (MoP Zee floor)
– Maxilla (blow out fractures!)
– Palatine (smallest bone)
– Zygomatic (strongest bone)
THE BONY ORBIT (cont.)
• LATERAL WALL: (Zee Great Side!)
– Zygomatic (strongest)
– Greater wing of Sphenoid
• MEDIAL WALL: (Eat @ M E L L S)
– Maxilla (blow out fractures!)
– Ethmoid (thinnest bone)
– Lacrimal (fossa for the lacrimal
sac)
– Lesser wing of Sphenoid (foramina
for optic nerve [II CN] to pass
through!)
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THE BONY ORBIT (cont.)
THE BONY ORBIT (cont.)
Cracks, Holes, & Depressions…
• Fissures = cracks in bones (the
Superior Orbital Fissure allows the
III, IV, V, & VI cranial nerves [CN]
access to the bony orbit)
• Foramina/Foramen = holes in
bones (the Optic Foramina is a hole
in lesser wing of Sphenoid that the
optic nerve [IICN] passes through)
• Fossa/Fossae = depressions
(“dents”) in bones (Lacrimal Fossa is
a dent in the lacrimal bone where
the lacrimal sac sits)
EXTRAOCULAR MUSCLES
EXTRAOCULAR MUSCLES (cont.)
• SIX (6) muscles for each eye
• They attach to the sclera of the eye
• “Job” is to move the eyes to keep objects of
interest lined up with the macula of each eye
– Goal is: Single Binocular Vision (SBV)
– Want to avoid: diplopia or suppression
resulting in monocular vision.
“Primary Position of Gaze” = Straight Ahead
EXTRAOCULAR MUSCLES (cont.)
There are four Rectus muscles for each eye:
Lateral Rectus (LR), Medial Rectus (MR), Superior
Rectus (SR), & Inferior Rectus (IR)
• Rectus muscles attach ANTERIOR to the equator; so
they “pull” the eye in the direction they “say”:
– Lateral Rectus (LR) pulls eye laterally (OUT), or
ABDUCTION
– Medial Rectus (MR) pulls eye medially (IN), or
ADDUCTION
– Superior Rectus (SR) pulls eye superiorly (UP), or
ELEVATION
Rectus Muscles
– Inferior Rectus (IR) pulls eye inferiorly
(DOWN), or DEPRESSION
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EXTRAOCULAR MUSCLES (cont.)
OBLIQUE MUSCLES
• There are two (2) OBLIQUES muscles for
each eye.
• OBLIQUES are “unique”; they move the eyes
OPPOSITE of what they “say”…
• SUPERIOR OBLIQUE (SO) makes the
eye look inferiorly (Depression) and
across the nose (intorsion)
• INFERIOR OBLIQUE (IO) makes the eye
look superiorly (Elevation) and across the
nose (extorsion)
EXTRAOCULAR MUSCLES (cont.)
• ExtraOcular Muscles (EOMs) are ‘innervated’ by
cranial nerves (nerves make the muscles work!)
• Which nerves ‘operate’ which muscles?
LR6 SO4 3
What!?
• Lateral Rectus = VI (6th) CN (Abducens)
• Superior Oblique = IV (4th) CN (Trochlear)
• All the rest = III (3rd) CN (Oculomotor)
IS YOUR BRAIN FULL YET?
So far, we have covered…
EXTRAOCULAR MUSCLES (cont.)
•Our eyes are
“YOKED”
together.
•The OD can’t
look up while
the OS looks
down!
•Where one
eye goes, the
other follows…
Next, the Visual Pathway
The body has AFFERENT neurons (nerves); they carry
‘sensory’ messages to the brain (like sight!)
•The three layers (or Tunics) of the eye: FIBROUS
TUNIC, UVEAL TRACT or (Vascular Tunic), and the
NERVOUS TUNIC
•-------------------------------------------------------•The Ocular Media: CORNEA, AQUEOUS HUMOR,
CRYSTALLINE LENS, & VITREOUS HUMOR
•-------------------------------------------------------•And then the… Ocular Adnexa, The Bony Orbit, and
the Extraocular Muscles
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The Visual Pathway: AFFERENT
The visual pathway is carrying an afferent message
to the brain:
1. RETINA
2. OPTIC NERVE (II Cranial Nerve)
3. OPTIC CHIASM (“chiasm = crossing”)
4. OPTIC TRACT (50% from OD; 50% from OS)
5. LATERAL GENICULATE BODY (LGB)
6. OPTIC RADIATIONS (fibers start to spread out)
7. VISUAL CORTEX (brain “interprets” visual
message here!)
Images that hit the retina are
upside down & backwards…
Here is another
way to look at
the Afferent
(visual) pathway
-----------Notice how 50%
of the visual
‘message’
crosses over to
the other side of
the head at the
OPTIC
CHIASM!
AFFERENT (visual) pathway (cont.)
Why do you care?
• Think about the tests you run on patients:
– Visual Acuity (VAs)
– Visual Fields (VFs)
– Cover Testing (CT)
– Extra Ocular Motility (EOMs)
– Pupillary Response
These all rely on an intact & functioning
AFFERENT (Visual) Pathway!
In conclusion, we covered the…
Thank You for your TIME!
• 3 Major Layers (Tunics) of
the Eye
• Ocular Media
• Ocular Adnexa
• The Bony Orbit
• Extraocular Muscles (EOMs)
• Visual Pathway
Lecturer:
M. Patrick COLEMAN, ABOC, COT
Kerrville, TX
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