this presentation provides the basic principles involved in anatomy of cornea and its functions.

1. Anatomy
Of
Cornea
By-
Husain J. Patanwala
Final year B.optom

2. Origin
The word cornea has come from
“Kerato”.
The term “Kerato” in Greek means
horn or shield like. Ancient Greek
used to believe that cornea is
derived from same material like that
of thinly sliced horn of animal.

3. Introduction
• Avascular, Transparent
• Accounts for 70% of the total refractive power of the
eye(+43D).
• Principle optical surface of the eye.
Refractive indices of different media
through which light enters the eye
Air 1.00
Tear fluid 1.33
Cornea 1.37
Aqueous humor 1.33
Lens 1.42
Vitreous 1.33

4. Dimensions
• Anterior Surface : Elliptical
Diameter: horizontal:11.75mm, vertical:11mm
• Posterior Surface: Circular
Diameter:11.5 mm
Microcornea
when HCD is less
than 10mm
Macrocornea
when HCD is more
than 13 mm

5. • Radius Of Curvature :
The anterior and posterior radii of curvature are 7.8mm
and 6.5 mm .
• Thickness :
The central corneal thickness is 0.52 mm, whereas
periphery is 0.67 mm thick. Central corneal thickness has
direct influence in IOP measurement. The central 5 mm of
the cornea forms the most powerful refracting surface

6. Histology:
6 layers
Anterior epithelium
Bowman’s membrane
Central Stroma
Duas layer
Descemet’s membrane
Endothelium

7. 1.Epithelium
• 50 -90µm thick.
Stratified squamous
type
• Consist of 5-6 layers

8. • Corneal epithelium sheds at regular interval. It takes
normally 7 days for replacement entire corneal epithelium
• Tight junctions in basal cells account for epithelium’s
transparency.
Layers
of
epithe
lium
Description Mit
otic
acti
vity
Basal
Cell
Single layer of
columnar cells
found adjacent
to basal layer
-
Wing
cell
2-3 layers of
cells with
elongated
process
-
Surface
cells
3 layers of
flattened
epithelial cells
with microvilli in
contact with the
tear film.
+

9. 2.Bowman’s membrane
• Binds the corneal stroma anteriorly with basement membrane
of epithelium.
• Not a true elastic membrane.
• Once destroyed , does not regenerate.
• Shows considerable resistance to infection and injury.

10. 3.Stroma
• 0.5mm thick.
• The stroma or substantia propria, occupies about 90% of the
total corneal thickness,
• Composed of collagen fibrils, keratocytes and extracellular
ground substances.
• The lamellae are arranged in many layers(200-250) and are
parallel to each other.

11. • Anterior 1/3 stroma : lamellae are thin( 0.5-30μm wide
,0.2-1.2 μm thick).
• Posterior 2/3 stroma : lamallae are larger ( 100- 200 μm
wide, 1 -2.5 μm thick).

12. Duas layer
• Was discovered by Dr.Harminder singh dua at
the university of nottingham in 2013
• It is the 4th layer 15 microns thick
• Strong layer and impervious to air

13. 5.Descemet’s membrane
• A strong homogenous layer.
• Basement membrane of endothelium.
• Made up of collagen and glycoprotien.
• Elastic.
• It can regenerate . Resistant to chemical agents, infection and
pathological processes.
• On posterior surface it shows Hassel Henle bodies,which
increase with advancing age.

14. 6.Endothelium
• Single layer of flat polygonal cells
• At birth cell density is around 6000 cells/sqmm
• With increasing age the no. of cells is reduced
• Involved in active secretion
and protein synthesis.
• Contains highest no. of
mitochondria next to photoreceptors.

16. Blood supply
• Cornea is an avascular structure.
• Small loops derived from the anterior ciliary vessels invade its
periphery for about 1mm and provide nourishment.
• These loops are not in cornea but in the subconjunctival
tissue which overlaps the cornea.

17. Nerve Supply
• The cornea is one of the most sensitive tissues of the body
and has one of the richest sensory nerve supplies in the body.
• It is supplied by long and short ciliary nerves
from the ophthalmic division of the trigeminal nerve.
• Most are concentrated in the anterior stroma beneath the
Bowman zone and send branches forward into epithelium
• Descemets membrane and endothelium are not innervated

20. At limbus,
•Corneal epithelium becomes bulbar conjunctival
epithelium
•Bowman's membrane becomes continuous with the
lamina propria of the conjunctiva and tenon's capsule.
•Stroma becomes sclera
•Descemets membrane becomes schwalbe's line.
•Endothelium lines the trabecular meshwork and
becomes continuous with the anterior surface of the
epithelium
Junction of Cornea and Sclera
Contains
1.Trabecular Meshwork
2.Canal of Schlemn

21. Transparency
• Tight junctions of the epithelial cells.
• Endothelial pump mechanism.
• Absence of blood vessels.
• Absence of pigments.
• Scarcity of cell nuclei in stroma.
• Uniform structure of stroma.

22. Corneal analysis
• Keratometer
• Confocal microscopy
• Specular microscopy
• AS-OCT
• Orbscan
• Aberrometer
• Pentacam
• Keratoscope
• Video keratoscope
• Oculus topographer
• Ocular response analyser
(OCA)
• 3netra
• Galilie

23. References
• Anatomy and Physiology of the Eye : Khurana
• Clinical Anatomy of the visual System : Remmington
• www.eophtha.com
Thank You