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Ocular Odyssey The Eyelashes and Beyond: Shane R. Kannarr, OD [email protected] Ocular Appendages Eyelids Protect from light Distribute tears Key Anatomy Meibomian glands oil glands mark the junction of skin and conjunctiva Gray line—between eyelashes and glands Punctum Lacrimale Located superior and inferior nasally in both eyes Drainage structure Eyebrows Protective Keep old men busy Conjunctiva A thin mucous membrane that lines the eyelids and sclera forms a space called the conjunctival sac Palpebral—lining of the eyelids Bulbar—lies in contact with the eyeball Lacrimal Caruncle—medial angle colorless hairs/accessory lacrimal gland Lacrimal System Lacrimal Gland— Orbital—larger section Palpebral—smaller section 12 ducts in to the superior fornix Numerous small accessory glands Tears Defense against microorganisms Regulate epithelial turnover Hormones to support lacrimal secretion/suppress immunology 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 Why do you care? 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 separates the eye from orbital 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 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 Clear as can be 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 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 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 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