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Ocular Odyssey
• The Eyelashes and
• Beyond:
By
Shane R. Kannarr,OD
Ocular Appendages
Eyelids
Protect from light
Distribute tears
Key Anatomy
Meibomian glands
oil glands mark
the junction of skin and conjuctiva
Gray line—between eyelashes and
glands
Punctum Lacrimale
• Located superior and inferior
nasally in both eyes
• Drainage structure
• **Caruncula lacrimalis**
Eyebrows
• Protective
• Keep old men busy
Conjunctiva
• A thin mucous membrane that lines
the eyelids and sclera forms a space
called the conjuctival sac
• Palpebral—lining of the eyelids
• Bulbar—lies in contact with the
eyeball
• Lacrimal Caruncle—medial angle
colorless hairs/acessory lacrimal
gland
Lacrimal System
• Lacrimal Gland—
– Orbital—larger section
– Palpebral—smaller section
– 12 ducts in to the superior
fornix
– Numerous small accessory
glands
Tears
Contain:
Lysozyme
IgA
Beta Lysin-bactericidal protein
Which:
Defense against microorganisms
Regulate epithelial turnover
Hormones to support lacrimal
secretion/suppress immonological
activity
Tears
• Work to:
– Keep the eye moist to aid in
refraction
– Lubricate with lipids for
movement
Tear Layers
• Thin superficial oily layer
secreted by the meibomian
glands/sebaceous
glands(Zeiss)/sweat(Moll)
• Watery layer (lacrimal glands)
• Mucin layer (conjunctival
goblet and lacrimal)
Tear drainage
• Punctum lacrimale
– Sets atop the papilla lacrimalis
– Superior and inferior
– Lacrimal Canaliculi
• Vertical and horizontal section
10mm long
• Ampulla-union of the two
• During blinking canaliculi are pulled
medially and compressed to act as a
pump
• Lacrimal Sac
– Situated in the lacrimal fossa
– Nasolacrimal duct-connects lower
end of the sac with the inferior
meatus of the nose
– Plica lacrimalis-keeps air out of
nasolacrimal sac
Tear Circulation
• Lids move tears over
cornea/tears do not follow the
lid
• During sleep the orbicularis
Oculi shortens the canaliculi
dilating the lacrimal sac and
pumping the tears off the eyes
The Eyeball
• Tenon’s Capsule
– Thin membrane that seperates
the eye from orbial fat
– Eyeball Dimensions
– Anterior-Cornea-1/6
– Posterior-Sclera 5/6
– 24mm anterior to posterior
diameter
Fibrous Layer
• Cornea
– Epithelium- 5 layers turns over
every 7 days
– Basement membrane
– Bowman’s layer-merges with the
stroma
Stroma
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90% of the thickness
Layers or Lamella
Run at 90 degrees
Does not rejuvenate
Allows LASIK to work
• Descmet’s membrane
– Posterior surface basement
membrane
Tidbits
• Endothelium-one layer thick
• Controls corneal hydration
• Avascular-gets nutrients from
the aqueous and O2 from tears
and peripheral vessels
• Major refractive surface
• Clarity comes from even
spacing/fluid is a problem
Tidbits
• Limbus-where cornea and
sclera meet
• Canal of Schlemm-around the
eye at the corneascleral
junction. Allows drainage
through the trabecular
meshwork
• Scleral spur
Sclera/Choriod
• 3 layers thick
• 1 mm thick
• Choriod—thin lining of the
inner surface of the sclera
• Nourishes the outer retinal
layer
Ciliary Body
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Two sections
Pars Plicata-anterior ridges
Ciliary processes
Anterior secretes aqueos
Posterior-zonules
Pars Plana-smooth
Ciliary MuscleMoves the ciliary body forward
for accomodation
Iris
• Pupillary margin-around the
pupil
• Ciliary margin-root of the iris
• 2 major muscles
– Sphinter-miosis
– dilator-mydriasis
Aqueous Flow
• Aqueous-clear fluid
• Formed by ciliary processes
• Flows between the suspensory
ligments through the pupil to the
anterior chamber
• Moves inferior/anterior to posterior
superior
• Anterior Chamber-behind the cornea
in front of the iris
• Posterior Chamber-lens to posterior
surface of the iris
Aqueos Drainage
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90% leaves by
Trabecular meshwork to
Canal of Schlemm to
Collector Channels to
Aqueos veins
• Meets metabolic needs for
avascular regions
Lens
• 4mm thick (thicker as we age)
• 15D of power (eye 58D)
• Anterior and Posterior poles
– Center points
– Equator-circumference
Lens “parts”
• Capsule-chief function to mold
the lens as the zonules contract
• Lens epithelium- move
metabolic materials in and out
• Makes lens fibers
• Lens Fibers
• Embryonic-earliest fibers
• Fetal
• Adult forms after birth always
changing
• Y sutures anterior are erect
• Y sutures posterior are inverted
• Lens cortex area with recently
formed fibers
Vitreous Body
• Occupies 4/5 of the eyeball
• Between the lens and the retina
• Hyloid fossa-depression for the
lens
• Dense cortex with a liquid
center
• 98% water
• Vitreous base-area where the
retina attaches at the ciliary
body/pars plana
The Retina
• The nervous coat is the internal
layer of the eyeball.
Photochemical transduction
creates nerve impulses that are
transmitted to the brain for
cortical processing. Purple in
color in living individuals
• Posterior portion is receptive
and ends at the orra serrata
• Anterior portion is
nonreceptive
The Retina
• Macula lutea-center of the posterior
portion. Depressed in the center to
form the fovea centralis
• RPE-retinal pigmented epithelium
single layer of cells Absorb light/aid
in the turn over of
photoreceptors(absorb light in an
antireflective method which stops
image degradation. Aid in blood
retina barrier
Neural Retina
• Groups of neurons
• Bipolar cells-contact cells to
ganglion cells
• Ganglion cells-second neurons carry
info from retina through lamina
cribosa
• Photoreceptors-rods and cones
• Horizontal cells-possible they
integrate visual stimuli
• Amacrine cells-excite lateral
ganglion cells/modulators of
photoreceptor signals
Retinal Layers
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1) Pigmented Epithelium
2) Rods and Cones
3) External limiting membrane
4) Outer nuclear layer
5) Outer plexiform layer
6) Inner nuclear layer
7) Inner plexiform layer
8) Ganglion cells
9) Nerve Fiber layer
10) Internal limiting membrane
Lamina cribosa
• Posterior opening
• One larger opening for the central
retinal artery and vein
• Increased IOP can cause bulging
and a cupped disk
• 3 other opening for one each for:
– Anterior Ciliary Arteries
– Exit of Vortex Veins
– Long and short ciliary nerves
7 Bones of the Orbit
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Maxilla
Palatine
Zygomatic
Sphenoid
Frontal
Ethmoid
Lacrimal
Lateral strongest/floor weakest
Sinuses
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Ethmoidal
Frontal
Maxillary
Sphenoid
• Most common site of orbital
cellulities
Visual Pathway
• “The retina, the optic nerve, the
optic chiasma, the optic tracts,
the lateral geniculate bodies,
the optic radiations, and the
visual cortex (area 17) make up
the pathway.”
• From the Clinical Anatomy of
the Eye” by Snell and Lemp
Tracing the Image
• Retina-Inferior nasal is Superior
temporal
• Optic Chiasma-Nasal crosses
• Optic tract-Retinal fibers line up
• Lateral Geniculate Body-relay
and integration
• Optic radiation
• The retina turns light into an
electrical nerve impulse
Musculature
• Primary Position-eye is straight
ahead
• Secondary-Up/down/lateral/medial
• Tertiary- up and out/down and in ect.
• Elevator-up
• Depressor-down
• Adduction-toward the midline
• Abduction-away from the midline
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Superior Rectus-elevator
Inferior Rectus-depressor
Medial Rectus-adductor
Lateral Rectus-abductor
Inferior obliqueelevates/abducts/extorsion
• Superior obliquedepresses/abducts/intorsion
Innervation
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Cranial nerves
II-Optic Vision
III-Oculomotor
Raises eyelids/moves eyeball
up/down/medial/contricts
pupil/causes accomodation
• IV Trochlear-assists in moving
eyeball down and lateral
• V Trigeminal-branch one is cornea
• Adbucent-Moves eyeball laterally
Muscles/Innervation
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Superior rectus-Oculomotor
Inferior rectus-Oculomotor
Medial rectus-Oculomotor
Inferior oblique-Oculomotor
Lateral rectus-abducents
• Superior Oblique-Trochlear
Blood Supply
• Ophthalmic Artery
– Branch of the Carotid
– Veins
• Superior and Inferior ophthalmic
• 2 anterior ciliary arteries go to
each rectus muscle