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Ocular Odyssey
• The Eyelashes and • Beyond:
ByShane R. Kannarr,OD
Ocular Appendages
EyelidsProtect from light
Distribute tears
Key AnatomyMeibomian glands
oil glands markthe 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:LysozymeIgABeta Lysin-bactericidal protein
Which:Defense against microorganismsRegulate epithelial turnoverHormones 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
• 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
• Two sections• Pars Plicata-anterior ridges• Ciliary processes• Anterior secretes aqueos• Posterior-zonules• Pars Plana-smooth• Ciliary Muscle-• Moves 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
• 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
• 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
• Maxilla• Palatine• Zygomatic• Sphenoid• Frontal• Ethmoid• Lacrimal
Lateral strongest/floor weakest
Sinuses
• 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
• Superior Rectus-elevator• Inferior Rectus-depressor• Medial Rectus-adductor• Lateral Rectus-abductor• Inferior
oblique-elevates/abducts/extorsion
• Superior oblique-depresses/abducts/intorsion
Innervation
• 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
• 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