Ocular Anatomy Intermediate
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
6. Accurately identify key ocular structures that compose
the visual pathway
Lecturer: M. Patrick COLEMAN, ABOC, COT
Topics to be covered:
Let’s get oriented first…
• Superior = UPWARD (or TOP)
• 3 Major Layers (Tunics) of the Eye
• Ocular Media
• Inferior = DOWNWARD (or BOTTOM)
• Ocular Adnexa
• Nasal / Medial = TOWARD NOSE
• The Bony Orbit
• Temporal / Lateral = TOWARD TEMPLE
• Extraocular Muscles (EOMs)
• Posterior = BEHIND (or Toward the BACK)
• Visual Pathway
• Anterior = IN FRONT (or Toward the Front)
FIBROUS TUNIC
3 Major Layers (Tunics) of EYE
• FIBROUS TUNIC
• Protective
layer of eye
• Tough &
fibrous
• UVEAL TRACT or (Vascular Tunic)
• 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!
• Cornea & sclera are the “same” material!
UVEAL TRACT (cont.):
Iris, Ciliary Body, Choroid…
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!)
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.
– When the ciliary muscles
CONTRACT, they release the
tension on the zonules so the
lens can grow thicker, (causing
us to focus, or accommodate)
allowing us to see things that are
NEAR.
UVEAL TRACT (cont.): CHOROID
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
NERVOUS TUNIC
The Retina…really!
That’s it.
Retina
• Retina lines posterior 2/3rds of the
inner 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.)
Nervous Tunic (i.e., RETINA)
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Nervous Tunic (i.e. RETINA) cont.
Nervous Tunic (i.e. RETINA) cont.
Retina has 10 layers
------------------It’s in-between the
VITREOUS &
CHOROID
------------------Key layers?
–
–
–
Retinal NFL
Photoreceptor
RPE
Retinal Detachment?
Most likely to
occur where
RPE &
Photoreceptors
come together!
Nervous Tunic (i.e. RETINA) cont.
• The photoreceptor layer contains the RODS & CONES
• Rods & Cones convert light into an electroelectro-chemical impulse
– That 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
Y G. BIV) which is between:
electromagnetic spectrum (ROY
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
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
TRIVIA QUESTION:
* You enter a dark movie theater.
How long does it take RODS to
kick in so you can start to ‘see’?
** Who adapts quickest – kids or
the elderly?
– 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.
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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.
• 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”…
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)
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
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OCULAR MEDIA - Cornea (cont.)
• Cornea
– Needs a good tear layer to transmit light well
– Good quality tears have three parts:
OCULAR MEDIA
(cont.):
TEAR FILM
• 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.)
OCULAR MEDIA – Aqueous Humor (cont.)
• AQUEOUS HUMOR
– Produced by the CILIARY BODY in “posterior
chamber” of the eye’
– Flows thru the pupil into “anterior
anterior chamber”
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 – Lens (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 - Vitreous (cont.)
OCULAR MEDIA – Vitreous (cont.)
• VITREOUS HUMOR
– Fills the posterior 5/6ths of the eye
– When we are young,
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)
floaters” it is usually debris in the
– When we see “floaters
vitreous that’s moving around
– What you have is all you get. If you lose vitreous, the
body will NOT make more!
So is that it? As they say on TV,
“But wait! There’s More!!!”
OCULAR ADNEXA
• Eyelids & Landmarks
• Ocular Adnexa
• Muscles of the eyelids
• The Bony Orbit
• Tarsal Plate & Glands
• Extraocular
Muscles (EOMs)
• Conjunctiva &
Lacrimal System
EYELIDS & LANDMARKS
LANDMARKS of the EYELIDS
• 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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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
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
ORBICULARIS OCULI !
• It is the primary muscle for closing the
eyelid
• Just remember:
Orbicularis Oculi CLOSES the eye!
QUESTION:
Which is the “PRIMARY” muscle for closing the
lids?
EYELIDS & LANDMARKS (cont.)
EYELIDS & LANDMARKS (cont.)
• TARSAL PLATE:
– Levator & Mueller’s muscle attach to this
– It is considered the “skeleton
skeleton” of the lid as it’s
made up of tough, fibrous tissue
– When the doctor “everts
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
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TARSAL PLATE IN THE LID
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.) - Glands
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;
Protection barrier to infection; keeps things
from getting ‘behind’ the eye
– Contains GOBLET CELLS that secrete MUCIN
OCULAR ADNEXA (cont.) - Conjunctiva
OCULAR ADNEXA (cont.) –
Lacrimal System
• LACRIMAL SYSTEM
– These are all the structures involved in the
production, distribution, & disposal of tears
– 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
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OCULAR ADNEXA (cont.)
LACRIMAL SYSTEM:
THE BONY ORBIT
• Additus Orbitae (the opening of the bony orbit)
• 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,
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.)
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!)
THE BONY ORBIT (cont.)
• Cracks, Holes, & Depressions…OH MY!
– Fissures = cracks in bones (the
Superior Orbital Fissure allows the III,
IV, V, and VI cranial nerves [CN]
access to the bony orbit)
– Foramina/Foramen = holes in bones
(the Optic Foramina is the hole in the
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)
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THE BONY ORBIT (cont.)
EXTRAOCULAR MUSCLES
• 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.)
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; because of that, they
pull the eye in the direction of their name:
• 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
• Inferior Rectus (IR) pulls eye inferiorly (DOWN), or DEPRESSION
EXTRAOCULAR MUSCLES (cont.)
• There are two (2) OBLIQUES muscles for each eye.
• OBLIQUES are “unique
unique”; they move the eyes OPPOSITE of
what they “say”…
• SUPERIOR OBLIQUE (SO) makes the eye look
inferiorly (Depression) and across the nose (intorsion
intorsion)
• INFERIOR OBLIQUE (IO) makes the eye look
superiorly (Elevation) and across the nose (extorsion
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)
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EXTRAOCULAR MUSCLES (cont.)
• Our eyes are
YOKED”
“YOKED
together.
• The OD can’t
look up while
the OS looks
down!
• Where one eye
goes, the other
follows…
IS YOUR BRAIN FULL YET?
So far, we have covered…
• The three layers (or Tunics)
Tunics of the eye:
FIBROUS TUNIC, UVEAL TRACT or (Vascular
Tunic), and the NERVOUS TUNIC
• -------------------------------------------------------• The Ocular Media: CORNEA, AQUEOUS
HUMOR, CRYSTALLINE LENS,
LENS & VITREOUS
HUMOR
• -------------------------------------------------------• And then the… Ocular Adnexa,
Adnexa The Bony Orbit,
and the Extraocular Muscles
Next, the Visual Pathway
The body has AFFERENT neurons (nerves) that
carry ‘sensory’ messages to the brain (like
like sight!)
sight!
•
The visual pathway is an
afferent message to the
brain; The seven (7) parts
of the afferent pathway:
1. RETINA
2. OPTIC NERVE
3. OPTIC CHIASM
4. OPTIC TRACT
5. Lateral Geniculate
Body (LGB)
1. OPTIC RADIATIONS
2. VISUAL CORTEX
Remember, 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!
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!
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