Cornea - 1
Upcoming SlideShare
Loading in...5
×
 

Cornea - 1

on

  • 2,401 views

 

Statistics

Views

Total Views
2,401
Slideshare-icon Views on SlideShare
2,401
Embed Views
0

Actions

Likes
3
Downloads
111
Comments
0

0 Embeds 0

No embeds

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment
  • µ

Cornea - 1 Cornea - 1 Presentation Transcript

  • CORNEA
  • CORNEA
    • Transparent,
    • Avascular,
    • Principle optical surface of the eye
    • Forms anterior one-sixth of the outer fibrous coat of the eyeball.
  • Dimensions
    • Anterior surface
    • Elliptical shape
    • Horizontal diameter:11.75 mm
    • Vertical diameter :10.6 mm
    • Posterior surface
    • circular shape
    • average diameter : 11.75 mm
    • 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
  • Histology
  • Histology
  • Epithelium
  • 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
  • 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
  • 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.
  • Endothelium
    • Single layer of flat hexagonal cells.
    • Mosaic pattern
    • Cell density : 2400 3000 cells/mm2
    • Contains active pump mechanism
    • Best evaluated by specular microscopy
  • Limbus
    • Anatomically the limbus refers to circumcorneal transitional zone of the conjunctivo-corneal and corneo-lscleral junction.
  • 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
  • Development of the cornea
    • Epithelium : surface ectoderm
    • Bowman`s layer, stroma , Endothelium & descemet`s membrane : mesenchymal cells derived from neural crest.
  • 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.
  • Corneal physiology
  • 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
  • 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.
  • 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
  • CONGENITAL ANOMALIES
    • Microcornea : horizontal diameter
    • < 10 mm since birth.
    • Megalocornea : horizontal diameter of the cornea is of adult size or 13 mm .
  • CONGENITAL ANOMALIES
    • Cornea plana : cornea is comparatively flat
    • since birth.
    • Congenital cloudy cornea
  • Keratitis
    • Any type of corneal inflammation –Keratitis
    • Types –
    • superficial –ant to Bowman’s membrane
    • Deep –stromal or interstitial or endothelitis
  • 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
  •  
    • Corneal edema
    • Keratic precipitates-deposition of leucocytes on the back of cornea
    • Hypopyon