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Home , Choroid, Ciliary body, Ciliary processes, Extraocular muscles, Lacrimal gland, Lacrimal sac

Ocular & Physiology Learning Objectives: 1. Correctly identify ocular structures around or within the 2. List the key functions of various ocular structures 3. Accurately point out key external landmarks on, or around the eye 4. Name major of the that surround the eye 5. List the six that control

Lecturer: M. Patrick COLEMAN, ABOC, COT 6. Accurately identify key ocular structures that Kerrville, TX compose the visual pathway

Topics to be covered: 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 • Posterior = BEHIND (or Toward the BACK) • Extraocular Muscles (EOMs) • Anterior = IN FRONT (or Toward the Front) • Visual Pathway

FIBROUS TUNIC 3 Major Layers (Tunics) of EYE

• FIBROUS TUNIC • Protective layer of eye • Tough & fibrous • UVEAL TRACT or (Vascular Tunic) • Two parts: – – • NERVOUS TUNIC

1 Fibrous Tunic (cont.): Layers of the Cornea Fibrous Tunic: 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 UVEAL TRACT (Vascular Tunic) • White in color (appears bluish in infants) • (colored part of eye) • Avascular (without blood vessels; (what look like blood vessels in the sclera are really in the EPISCLERA which lays on top of the • (behind iris) sclera) • Makes up posterior 5/6th of fibrous tunic • (can see it on retinal photos, • Very tough! and OCT scans of the !) • Cornea & sclera are the “same” material!

UVEAL TRACT (cont.): UVEAL TRACT (cont.): IRIS Iris, Ciliary Body, Choroid… • 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

2 UVEAL TRACT (cont.): Ciliary Body UVEAL TRACT (cont.): Ciliary Body • Located just behind the iris, at its base • produces aqueous humor constantly (keeps our eye ‘filled’ with fluid so it remains “inflated”) • Ciliary Muscles control the focusing of the – 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 UVEAL TRACT (cont.): CHOROID (processes & muscles)

UVEAL TRACT (cont.): CHOROID NERVOUS TUNIC • Supplies blood to the iris, The Retina…that’s it! ciliary body, inner retina & • Retina ‘lines’ the back 2/3rds of eye inner sclera • 10 layers thick; all the layers are transparent except • The “CHOW HALL” of the the RPE (retinal pigment epithelial) layer eye - brings nourishment • Retina lies on top of the choroid & oxygen • It’s in contact with the vitreous humor (fluid) • Contains cells that respond to light (photoreceptors); –“Sandwiched” between the two (2) types – CONES & RODS SCLERA and the RETINA • 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 .)

3 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 cells, to the nerve fiber layer (NFL) – Then it goes to the brain via the (II CN) • Rods & Cones only “” wavelengths in the visible electromagnetic spectrum (ROY G. BIV) which is between: 400nm (VIOLET) to 700nm (RED).

Nervous Tunic (i.e. RETINA) cont. Nervous Tunic (i.e. RETINA) cont. • CONES are for bright (photopic) • RODS are for dim conditions; can see color & fine (scotopic) conditions; detail They provide a poor – There are approximately 6 million cones in the retina image but have a great – The (center of ability to sense Macula) contains ONLY movement CONES! – There are – Cones emit a chemical called approximately 120 IODOPSIN TRIVIA QUESTION: million rods in the Trivia Question: * When entering a dark retina. • What percentage of MEN are movie theater, whose “colorblind”? – Rods emit a chemical will ‘dark adapt” the • What percentage of WOMEN called RHODOPSIN quickest: A young person are “colorblind”? or an elderly person?

4 Nervous Tunic (i.e. RETINA) cont. Nervous Tunic (i.e. RETINA) cont. • The layer closest to the • The retina is CLEAR, with the vitreous humor is the exception of the Retinal Pigment RETINAL NERVE Epithelium (RPE) layer which, like FIBER LAYER (NFL) the iris, contains pigment • This layer contains the – The RPE layer is the “garbage coming from man”: every part of the retina • It absorbs excess light • At the optic nerve, the –AND nerve fiber bundles are most concentrated • It must remove the chemicals superiorly & inferiorly emitted by the rods (rhodopsin) and cones • Ever do an OCT scan of (iodopsin) as these chemicals the area around the optic nerve head (ONH) of a are TOXIC TO THE RETINA. patient? Why?

Nervous Tunic (i.e. RETINA) cont. Zeiss OCT scan • As the nerve fibers of optic nerve approach the optic head (ONH) of disk, they start to both eyes: bundle closer Green = GOOD together and form the cable to the brain Yellow = we call the OPTIC BORDERLINE NERVE (II CN) Red = BAD • In GLAUCOMA, these (glaucoma?!) nerve fibers die off

Nervous Tunic (i.e. RETINA) cont. So that’s it, right? HARDLY! • 9/10ths of the Retinal blood • The TUNICS of the eye are supply comes just “layers” of the main from the functional components. CENTRAL • There are many other RETINAL “parts” that make up the eye (CRA) and help it work correctly. • Time to look at the “rest of the eye”…

5 OCULAR MEDIA OCULAR MEDIA - Cornea (cont.) • These are the clear structures of the • Cornea eye light must – Needs a good tear layer to transmit light well pass through to – Good quality have three parts: get to the retina. • Lipid (oil) layer (top/outermost layer) - • They are the: keeps aqueous layer from evaporating – CORNEA away too quickly – AQUEOUS • Aqueous layer (middle layer) - water HUMOR portion of tear (thickest layer!) – LENS • Mucin (mucous) layer (innermost/against – VITREOUS cornea) - keeps tears ‘stuck’ against HUMOR cornea

OCULAR MEDIA OCULAR MEDIA – Aqueous Humor (cont.) (cont.): TEAR FILM AQUEOUS HUMOR • Produced by the CILIARY BODY in “posterior chamber” of the eye’ • Flows thru the into “anterior chamber” • Provides nourishment to Endothelial layer of the cornea & maintains “pressure” in the eye • Drains thru the and into the 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 • form in this structure (BUMMER!) • Approximately +18.00D to +21.00D of power

6 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 &“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 “” 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)

EYELIDS & LANDMARKS OCULAR ADNEXA • are the folds of tissue that cover the eye itself. Their primary purpose is… • Eyelids & – PROTECTION!!! Landmarks – Limit amount of light entering the eye • Muscles of the (giving the pupil an “assist” @ times) eyelids –Keep dust & dirt out of the eye (& fingers & • Tarsal Plate & racquetballs & fish hooks &…well, you get Glands the idea!) • & Lacrimal System – = ‘early warning’ sensors • (Which lid has MORE lashes? UPPER or lower?)

7 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”!) & the • MUSCLE OF MUELLER – The III CN () “operates” these nerves (Which muscle is the PRIMARY worker here?)

LEVATOR PALPEBRAE EYELIDS & LANDMARKS (cont.) SUPERIORIS (LEVATOR)! • MUSCLES of the EYELIDS (cont.): –To CLOSE the lids, we use the: • A way to remember? • & the… • Mueller gets on the LEVATOR to go UP & fix the oculoMOTOR on the 3rd (III) floor • RIOLAN’S muscle –The VII CN () “operates” these • Levator OPENS the eyelids two muscles – Mueller helps QUESTION: – III CN (Oculomotor nerve) controls them Which is the “PRIMARY” muscle for closing both the lids?

EYELIDS & LANDMARKS (cont.) ORBICULARIS OCULI

• It is the primary muscle for closing the

Just remember: Orbicularis Oculi CLOSES the eye!

8 EYELIDS & LANDMARKS (cont.) TARSAL PLATE IN THE LID

• TARSAL PLATE: – Levator & Mueller’s muscles attach here – 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

9 OCULAR ADNEXA (cont.)-Lacrimal System OCULAR ADNEXA (cont.) LACRIMAL SYSTEM LACRIMAL SYSTEM: • Seven (7) distinct structures involved in the production, distribution, & disposal of tears 1) 2) Lacrimal Canal (Ducts) 3) Conjunctival Sac 4) Puncta (upper & lower) 5) Canaliculi 6) 7) NasoLacrimal

THE BONY ORBIT THE BONY ORBIT (cont.) • 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, fat, lacrimal gland and vascular supply) • Bony orbit is comprised of a: – ROOF (lesser wing of SPHENOID & FRONTAL) – FLOOR (, 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 • LATERAL WALL: (Zee Great Side!) the roof) – Zygomatic (strongest) – Lesser wing of Sphenoid – Greater wing of Sphenoid (foramina for optic nerve [II CN] to pass through!) • MEDIAL WALL: (Eat @ M E L L S) – Frontal (fossa for lacrimal gland) – Maxilla (blow out fractures!) – Ethmoid (thinnest bone) • FLOOR: (MoPZee floor) – Lacrimal (fossa for the lacrimal sac) – Maxilla (blow out fractures!) – Lesser wing of Sphenoid (foramina – Palatine (smallest bone) for optic nerve [II CN] to pass – Zygomatic (strongest bone) through!)

10 THE BONY ORBIT (cont.) THE BONY ORBIT (cont.) Cracks, Holes, & Depressions… • = cracks in bones (the Superior Orbital allows the III, IV, V, & VI [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 where the lacrimal sac sits)

EXTRAOCULAR MUSCLES EXTRAOCULAR MUSCLES (cont.)

• SIX (6) muscles on 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 (SBV) • Want to avoid: or suppression resulting in monocular vision. “Primary Position of Gaze” = Straight Ahead

EXTRAOCULAR MUSCLES (cont.) Rectus Muscles 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 – Inferior Rectus (IR) pulls eye inferiorly (DOWN), or DEPRESSION

11 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 (cont.)

• ExtraOcular Muscles (EOMs) are ‘innervated’ by •Our eyes are cranial nerves (nerves make the muscles work!) “YOKED” • Which nerves ‘operate’ which muscles? together. LR6 SO4 3 •The OD can’t What!? look up while the OS looks th • Lateral Rectus = VI (6 ) CN (Abducens) down! th • Superior Oblique = IV (4 ) CN (Trochlear) •Where one • All the rest = III (3rd) CN (Oculomotor) eye goes, the other follows…

IS YOUR BRAIN FULL YET? Next, the Visual Pathway So far, we have covered… 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), & the NERVOUS TUNIC ------• The Ocular Media: CORNEA, AQUEOUS HUMOR, CRYSTALLINE LENS, & VITREOUS HUMOR ------• And then the… Ocular Adnexa, The Bony Orbit, & the Extraocular Muscles

12 The Visual Pathway: AFFERENT Here is another The visual pathway is carrying an afferent message to the brain: way to look at the Afferent (visual) 1. RETINA pathway 2. OPTIC NERVE (II Cranial Nerve) ------3. OPTIC CHIASM (“chiasm = crossing”) Notice how 50% 4. OPTIC TRACT (50% from OD; 50% from OS) of the visual ‘message’ 5. LATERAL GENICULATE BODY (LGB) crosses over to 6. OPTIC RADIATIONS (fibers start to spread the other side of out) the head at the 7. VISUAL CORTEX (brain “interprets” visual OPTIC CHIASM! message here!)

Images that hit the retina are AFFERENT (visual) pathway (cont.) upside down & backwards… 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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