Thursday, November 20, 2008

- cornea.


* Definition :

It is a colorless (transparent) structure

covering the anterior 1/6 of the eye ball.

*Development of the cornea:

  • Surface ectoderm forms the epithelium of the cornea.
  • Mesoderm gives rise to the corneal stroma.
  • Neural crest cells gives rise to the corneal Endothelium.

**Characters of the cornea :-

- colorless (transparent) structure and has a smooth surface.

- A vascular structure.

- Highly innervated by non-myelinated trigeminal nerve fibers.

-The most powerful refractive media of the eye

( 42+ diopters ).

- Diameter :-

  • Horizontal = 12mm
  • vertical = 11mm Why…?
Due to scleral overlapping on upper

& lower sides of the cornea.

- It is not uniformly curved How…?

>>the central or optical zone having a smaller radius of

curvature than the peripheral parts, and the

posterior surface is more strongly curved than the anterior.

>> Ant radius of curvature = 7.7 mm

>> Post radius of curvature = 6.6 mm

>>Thus the cornea is thinner (0.6 mm) at its

center than near its margin (1 mm).

see you,

Dr Ibrahim

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