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Anatomy for lu4

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OSI 212 Ophthalmology

OSI 212 Ophthalmology

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  • The bony orbit provides a container of the globe and gives protection to its contents.
  • Fixed volume means, when there is a tumor or swelling … the eyeball is pushed forward resulting in proptosis and when one of the orbital walls are damaged such as in orbital fractures, this results in increase in its relative volume resulting in posterior displacement of the globe or enophthalmos
  • Supraorbital foramen is located at the medial third of the superior margin of the orbit.
  • Supraorbital foramen is located at the medial third of the superior margin of the orbit.
  • Main function of the eyelid is for protection, contains oil gland (Meibomian glands) which form the outermost layer of the tear film, contains the tear drainage, cosmesisMuscles that open the eye are : levatorpalpebraesuperioris, mullers muscle, frontalis muscle ; close the eye: orbicularis ; corrugator supercilii ; procerus muscle
  • The amount of tears present in our eye is determined by tear production, evaporation, and drainage. The lacrimal drainage system is composed of the punctum, canaliculus and nasolacrimal duct.
  • Palpebral begins at the mucocutaneous junction of the eyelid and covers the inner eyelid surface; adheres firmly to the tarsusFornix: tissues are redundant and freely movableBulbar Conjunctiva is movable but fuses with the Tenons capsule and inserts into the limbus
  • Greater variation in fibril separation and diameterGreater degree of fibril interweave
  • Stem cells in the limbus
  • Zonular fibers attah primarily in the valleys of the ciliary processes but also along the pars plana
  • Retina occupies the inner aspect of the posterior 2/3s of the human eye.
  • The sensory retina is made of layers of cells composed of receptor neurons and glial cells to receive, modulate and transmit images to the brain.Light received by photoreceptors are then processed by modulator cellsTransmitter cells: Transmit the visual impulses from bipolar and amacrine cells to the midbrain
  • Outer plexiform to the RPE

Anatomy for lu4 Anatomy for lu4 Presentation Transcript

  • Anatomy of the Eye Dr. Alexander D. Tan UP-PGH Department of Ophthalmology and Visual Sciences
  • ObjectivesDescribe the different anatomic parts of the humaneye Bony Orbit Eyelids and Lacrimal Drainage System Extraocular Muscles Cornea and Conjunctivae Uvea, Choroid and Sclerae Retina
  • Bony Orbit
  • Human OrbitPear shaped ; Volume: 30 ccOrbital entrance is 35mm in height and 45mm widthMaximum width is 1 cm behind the orbital marginDepth 40 to 45mm, medial walls are parallel, lateralwalls are 90 degrees apartBones: Frontal, Zygomatic, MaxillaryBone, Ethmoid, Sphenoid, Lacrimal and Palatine
  • Bones of the OrbitRoof: Frontal bone and lesser wing of the SphenoidboneMedial Wall: Frontal Process of MaxillaryBone, Lacrimal Bone, Ethmoid Bone and lesser wingof SphenoidOrbital Floor: Maxilla, Palatine, orbital plate of theZygomatic BoneLateral Wall: Zygomatic and greater wing of theSphenoid Bone
  • Foramina, Ducts, Canals and Fissures Optic Foramen (lesser wing of Sphenoid): optic nerve, ophthalmic artery and sympathetic fibers from carotid plexus Supraorbital foramen: blood vessels and supraorbital nerve (branch of CN V1) Anterior Ethmoidal Foramen, Posterior Ethmoidal Foramen and Zygomatic Foramen Nasolacrimal Duct Infraorbital Canal: infraorbital nerve (V2)
  • Foramina, Ducts, Canals and Fissures SOF: lacrimal nerve of V1, frontal nerve of V1, CN IV, SOV; suprior and inf divisions of CN III, nasociliary branch of V1, sympathetic roots of ciliary ganglion and CN VI, inferior ophthalmic vein IOF: infraorbital and zygmatic branches of V2, orbital nerve from pterygopalatine ganglion and inferior ophthalmic vein
  • Eyelids and Lacrimal Drainage
  • Lacrimal Drainage System
  • Extraocular Muscles
  • Extraocular Muscles7 EOMs: Medial Rectus, Lateral Rectus, SuperiorRectus, Inferior Rectus, Superior Oblique, InferiorOblique and Levator Palpebrae SuperiorisInserts anteriorly at the Globe: MR, IR, LR, SR (spiralof Tillaux)SO: passing through the trochlea to sclera under SRIO: inserts postero-infero-temporal quadrantAnnulus of Zinn: 4 Recti muscles; above is LevatorSO: sphenoid bone, IO maxillary bone
  • Innervation of EOMsLateral Rectus: CN VISuperior Oblique: CN IVRest: CN III
  • Conjunctivae3 Geographic Zones: Palpebral, Forniceal andBulbarMucous membrane : non keratinizing squamousepithelium with numerous goblet cells and a thinrichly vascularized substantia propria containinglymphatic vessels, plasma cells, macrophages andmast cells.
  • Eyelids and Lacrimal Drainage
  • GlobeNot a true sphere: ROC Cornea: 8mm ROC Sclera:12mm forming an oblate spheroidAxial length is 23 to 25 mm; transverse distance is 24mm; total volume os 6.5 to 7 mlThree Cavities Anterior Chamber: 3 mm deep; 200 ul Posterior Chamber 60 ul Vitreous Cavity (2/3 of the volume of the eye) 5 to 6 mlEyeball is Cornea anteriorly and Sclera posteriorly
  • Sclera / UveaSCLERA : Opaque and white Thinnest just behind the insertion of the rectus muscles ; 1 mm posteriorly, and ; sieve-like at lamina cribrosa Generally avascular Lamina fuscaUVEA: choroid, ciliary body, iris Highly vascular, nutritive and supportiveRETINA: innermost layer
  • CorneaMain refractive element of the eye 43 diopters12 mm horizontal ; 11 mm vertical1mm thick at the periphery, 0.5 mm thick at thecenterCentral 1/3 is nearly spherical (4mm)Posterior cornea more curved than the anteriorEPITHELIUM: Nonkeratinized, stratified, squamousepithelium ; 2 to 3 layers of polygonal “wing” cells;basal cell layerBOWMANS LAYER: tough layer , does not regenerate
  • CorneaSTROMA: 90% of total thickness; composed ofcollagen producing keratocytes, groundsubstance, and collagen lamellae; regularity of fibersmaintain transparencyDESCEMET’S MEMBRANE: basal lamina of the cornealendothelium Increases thickness with age Peripheral excresences (Hassal Henle warts) Central excresences (corneal gutata)
  • CORNEAENDOTHELIUM: single layer of hexagonalcells, 500,000 cells (3,000 cells/mm2)Maintains corneal transparency and deturgescenceMitosis is rare, number decreases with age
  • UVEAL TRACTMain vascular compartment of the eyeThree attachments to the sclera : scleral spur, exitpoints of vortex veins and optic nerveIRIS: determines the size of the pupil, eyecolor, sphincter muscle and dilator muscleCILIARY BODY: formation of the aqueous humor, lensaccomodation, trabecular and uveoscleral outflow ofaqueous humor Pars plana: 4 mm from limbus ; Pars plicata 70 radial ciliary processes Non pigmented epithelium: aqueous formation Ciliary muscle: longitudinal, radial and circular
  • UVEAL TRACTCHOROID: nourishes the outer portion of the retina Three layers: choriocapillaries, middler layer of small vessels, outer layer of large vessels Long and short posterior ciliary arteries; anterior ciliary arteries BRUCHS MEMBRANE: fusion of the basal lamina of RPE and choriorcapillaries of the choroid
  • Crystalline LensAvascular, 4mm thick and 9 mm in diameterLens Capsule, outer cortex and inner nucleus.Held in place by zonular fibersSecondary refractive element of the eyeTurns into a cataract
  • RetinaThin, semi-transparent, multilayered sheetReceptor and Processor of imagesAnterior margin: ora serrata , strongly attached at the oraserrata and optic disc0.1 mm thick at the ora serrata and 0.56mm thick at theposterior poleMACULA: center of the posterior pole 3 mm of yellowish pigmentation FOVEA : center of the macula; depression seen producing a FOVEAL REFLEX FOVEOLA: most center portion of FOVEA : all photoreceptors are cones, thinnest part of the retina
  • RetinaComposed of RETINAL PIGMENT EPITHELIUMAND SENSORY RETINARPE: single layer of hexagonal cells, functions totrap lightPhotoreceptors: Rods for dark vision and Conesfor light and color visionModulator Cells: Bipolar, Amacrine andHorizontal cellsTransmitter Cells: Ganglion Cell
  • 10 Layers of the Retina1. Internal limiting membrane2. Nerve fiber layer3. Ganglion cell layer4. Inner plexiform layer5. Inner nuclear layer6. Outer plexiform layer7. Outer nuclear layer8. External limiting membrane9. Photoreceptor layer10. Retinal Pigment Epithelium
  • Retina / VitreousBlood supply Choriocapillaries: outer third of the retina Central retinal artery: inner 2/3 of the retinaVITREOUS: 2/3 volume and weight of the eye 99% water plus collagen and hyaluronic acid