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