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Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
Cornea
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Cornea

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    • 1. CORNEA
    • 2. CORNEA
      • Transparent,
      • Avascular,
      • Principle optical surface of the eye
      • Forms anterior one-sixth of the outer fibrous coat of the eyeball.
    • 3. Dimensions
      • Anterior surface
      • Elliptical shape
      • Horizontal diameter:11.75 mm
      • Vertical diameter :10.6 mm
      • Posterior surface
      • circular shape
      • average diameter : 11.75 mm
    • 4.
      • Thickness
      • at centre : 0.52 mm
      • at periphery : 1.2 mm
      • Radius of Curvature
      • central 5 mm of the cornea forms powerful refracting surface of the eye.
      • Anterior : 7.8 mm
      • Posterior : 6.5 mm
      • Refractive power
      • 45 diopters
      • 3/4 th of the total refractive power (60 D)
      • Refractive Index
      • 1.376
    • 5. Histology
    • 6. Histology
    • 7. Epithelium
    • 8. Bowman's membrane
      • Acellular mass of condensed collagen fibrils
      • Thickness : 8 – 14 microns
      • Shows considerable resistance to infection and injury
      • But once destroyed, does not regenerate
    • 9. Stroma
      • Thickness : 0.5 mm
      • 90 % of total corneal thickness
      • Consists of collagen fibrils (lamellae) and cells embedded in hydrated matrix of proteoglycans (ground substance).
      • Lamellae arranged parallelly (200 – 250 layers)
      • Cells : keratocytes
    • 10. Descemet`s membrane
      • Represents the basement membrane of the endothelium
      • Made up of collagen and glycoprotein
      • Thickness :10-12 µm
      • Very resistant to chemical agents, trauma, infection and pathological processes.
      • Maintains integrity of the eyeball
      • It can regenerate, when destroyed.
    • 11. Endothelium
      • Single layer of flat hexagonal cells.
      • Mosaic pattern
      • Cell density : 2400 3000 cells/mm2
      • Contains active pump mechanism
      • Best evaluated by specular microscopy
    • 12. Limbus
      • Anatomically the limbus refers to circumcorneal transitional zone of the conjunctivo-corneal and corneo-lscleral junction.
    • 13. Blood & Nerve supply
      • Blood supply
      • Avascular structure
      • Small loops derived from the superficial and deep plexus, invade its periphery for about 1mm and provide nourishment
      • Nerve supply
      • Has rich sensory supply
      • Long ciliary nerves branches of nasociliary nerve (a branch of ophthalmic division of trigeminal nerve)
      • Non myelinated
    • 14. Development of the cornea
      • Epithelium : surface ectoderm
      • Bowman`s layer, stroma , Endothelium & descemet`s membrane : mesenchymal cells derived from neural crest.
    • 15. Corneal physiology
      • Two primary physiologic functions
      • Act as a powerful refracting medium, transmits light in an orderly fashion for proper image formation.
      • Protects intraocular contents.
    • 16. Corneal physiology
    • 17. Corneal transparency
      • Anatomic / physical factors
      • Uniform and regular arrangement of corneal epithelium
      • Regular arrangement of stroma
      • Corneal avascularity, non myelinated nerve fibres
      • Normal tear film
      • Physiological factors
      • Relative state of corneal dehydration
      • Stromal swelling pressure
      • Normal intraocular pressure
      • Endothelial pump mechanism
    • 18. Tear film
      • Three layers
      • Mucus layer : innermost & thinnest
      • 0.02 -0.05 microns
      • secreted by conjunctival goblet cells
      • Aqueous layer : thickest
      • 6.5 – 7.5 microns
      • secreted by main & accessory lacrimal glands
      • Alkaline & antibacterial
      • Lipid or oily layer : outermost
      • 0.1 microns
      • secreted by meibomian, zeis & moll glands.
    • 19. Functions of the tear film
      • Keeps the cornea & conjunctiva moist
      • Provides oxygen to the cornea
      • Washes away debris & noxious irritants
      • Prevents infection due to presence of antibacterial substances
      • Facilitates smooth movements of the lids over the globe
    • 20. CONGENITAL ANOMALIES
      • Microcornea : horizontal diameter
      • < 10 mm since birth.
      • Megalocornea : horizontal diameter of the cornea is of adult size or 13 mm .
    • 21. CONGENITAL ANOMALIES
      • Cornea plana : cornea is comparatively flat
      • since birth.
      • Congenital cloudy cornea
    • 22. Keratitis
      • Any type of corneal inflammation –Keratitis
      • Types –
      • superficial –ant to Bowman’s membrane
      • Deep –stromal or interstitial or endothelitis
    • 23. Few terminologies
      • Abrasion-defect in the epithelium
      • Corneal ulcer-defect in the epithelium+inflammation+surrounding tissue necrosis.
      • Corneal scar or opacity-healing of any corneal injury beyond the level of bowman’s membrane
      • Types-nebula, macula and leucoma
    • 24.  
    • 25.
      • Corneal edema
      • Keratic precipitates-deposition of leucocytes on the back of cornea
      • Hypopyon

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