The document provides an overview of the anatomy of the cornea. It begins by introducing the cornea as the transparent outer layer of the eyeball that allows for vision. The summary is as follows: 1) The cornea consists of 5 layers - epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium. 2) The stroma makes up around 90% of the corneal thickness and contains collagen fibrils and keratocyte cells. 3) The cornea has no blood vessels and receives nourishment by diffusion from the aqueous humor and vessels at its edges. 4) Knowledge of corneal anatomy is important for diagnosing and treating eye diseases as

1. ANATOMY OF THE CORNEA
Presentation is made by
Dr. Sohel Mahmud
MBBS, DO.
Eye specialist & Surgeon,
Dhaka, Bangladesh.

2. Introduction
We obtain more than 80% of our information from the external
world by means of visual function.
It is the transparent, avascular, watchglass-like
structure of anterior outer coat of eyeball.
Cornea serves as the gateway of light into the
eye.

3. Ancient Greek
used to believe
that cornea is
derived from
thinly sliced
horn of animal.
‘‘Kerato’’ in
Greek means
horn or shield
like.
Medical terms
related to the
cornea often
start with the
prefix "kerat-"
The word Cornea comes
from “Kerato”.

4. Corneal epithelium-
From surface ectoderm
Descemet’s mem and
endothelium-
mesenchymal cells from
margin of optic cup
Bowman’s layer and
stroma- mesenchymal
cells insinuteate between
surface ectoderm and
developing lens
Cornea
Corneal development

5. 1.Cornea forms anterior one-sixth of the outer coat of eye
ball.
Gross feature of cornea

6. Gross feature cont…
2. Anterior surface is elliptical with a horizontal diameter
of
11.7mm and vertical diameter of 10.6mm.
3. Posterior surface is circular with an average diameter of
11.7mm.
HD=11.7mm
VD=10.6mm
Anterior aspect Posterior aspect
AD=11.7mm

7. Gross feature cont…
4. Thickness in the center is 0.52mm while at the periphery
is 0.67mm.
5. The radius of curvature of anterior surface is 7.8mm and
posterior surface 6.5mm.
Thickness of the cornea
7.8mm
6.5mm
Radius of curvature of the cornea

8. Gross feature cont…
6. Refractive power of the anterior surface is +48.8 D
and of its posterior surface is —5.8 D.
So, net refractive power is +43 D.
7. Refractive index is 1.376.

9. Gross feature cont…

10. Histology
Cornea consist of 5
distinct layers (from
anterior to posterior)–
1. Epithelium
2. Bowman’s membrane
3. Stroma
4. Descemet’s membrane
5. Endothelium

12. Epithelium
 Represents 10 percent of the
corneal thickness.
 About 50-90µm thick and
consist of 5-6 layers of cells.
 It is stratified squamous
nonkeratinised epithelium.
Divided into -
• Superficial squamous cells layer
• Middle wing cells layer
• Inner basal cells layer

13. Epithelium cont…
Basal layer
 Comprises tall columnar
polygonal shaped cells
arranged in a palisade
like manner on
basement membrane.
 Attached to the
basement membrane
with hemidesmosomes
and each-other with
desmosomes.
 Capable of mitosis.

14. Epithelium cont…
Flatten cells layer
 2 most superficial layers
 Long thin cells with
flatten nuclei.
 Most superficial cells
have microvilli.
Wing cells layer
 2-3 layers of pollyhedral
cells
 Flatten and parallel nuclei

15. Corneal epithelial surface
showing microvilli and
mcroplicae
Corneal epithelium

17. Bowman's Layer
( Thickness 8-14 µm –
composed of randomly
arranged collagen fibers
)
 Named after English anatomist and
ophthalmologist Sir William
Bowman.
 Acellular tough membrane like zone.
 Condensed superficial part of stroma.
 It is not a basement membrane.
 Once destroyed it cannot be
regenerated.

18. Composed of
collagen fibrils,
keratocytes and
extracellular ground
substances.
Collagen
components
constitute more than
70% of the dry
weight of cornea.
Stroma
90% of total
corneal
thickness
stroma

19.  Collagen fibrils with uniform 25- to
35-nm diameter - arranged in flat
bundles called lamellae.
 Distance between two fibers is also
highly uniform (41.5nm)
 Collagen fibers form approximately
300 lamellae in corneal stroma.
Collagen fibrils

20. Types of collagen fibers present in the different layers of the cornea

21.  Extracellular matrix or ground
substances found - mainly
glycosaminoglycan.
 Primary glycosaminoglycans of
the stroma
- Keratin sulfate (65%) and
- Chondroitin sulfate.
Ground substances

22.  Occupy 3-5% of the stromal volume.
 Flattened cell body, eccentric nucleus and
long branching processes.
 Found scattered in between the lamellae of
collagen fibers.
 Synthesize collagen and extracellular
matrix
components.
Keratocytes
(corneal fibroblasts ---major
cell type of the stroma)
Cellular component

23. Descemet's Membrane
 Named after French physician Jean
Descemet (1732–1810).
 Thick basement membrane secreted by
the endothelium.
 Produced constantly - thickens
throughout life (5µm at birth /10-12
µm in adult).
 No elastic fibers present – Though
exhibit elastic property due to the
particular arrangement of collagen
fibers.
Descemet’s
membrane

24. Descemet's Membrane cont.
 Terminates near limbus as
Schwalbe’s line.
 On electronmicroscope- divided 2
distinct zone.
 Once destroyed - can regenerated.
 Tough layer - resistant to enzymatic
degradation by phagocytes and
toxins.
 Does not adhere strongly to the
stroma - surgically dissected as a
sheet.
Descemet’s
membrane

25.  Single layer, hexagonal, cuboidal
cells.
 Mosaic pattern- best seen in
specular microscopy.
 Possess ion transport system -
known as endothelial pump.
 Cannot divide or replicate.
Endothelium
Corneal endothelium

26. Corneal endotheliumcont..
 Interconnected with each other with various
junctional complexes .
 With ageing, the cell density of the endothelium
decreases.

27. 6000

28. Aging Changes in the corneal layers
With advancing age-
 Cornea becomes less translucent and dust like
due to condensation of stroma.
 Bowman’s and Descemet’s membrane are also thickened.
 Arcus senilis appear.
 Hassall Henle bodies are found periphery of the
descemet’s membrane.

29. Blood supply
Cornea is avascular and devoid of
lymphatic
drainage.
It is nourished by diffusion from aqueous
and capillaries at it’s edge.

30. Nasociliary nerve branch of ophthalmic division of trigeminal
nerve
Long ciliary nerves enter the eyeball around optic nerve
Runs anteriorly in suprachoroida space, a short distance from
limbus, they pierce the sclera
Divides dichotomously, connect with each other & with
conjunctival nerves to form pericorneal plexus of nerves
Nerve supply

31. After going 1-2mm in the stroma corneal nerves loss their myalin
sheath covering and devided dichotomusly and form 3 nerve
network.
60-80 mylinated trunks from pericorneal plexus enter the cornea
1. Stromal plexus (in mid stroma)
2. Sub epithelial plexus
(located in between Bowman’s layer and anterior stroma)
3. Intra epithelial plexus
Nerve fibers terminate as naked nerve endings between tightly
packed epithelial cells.
Nerve passes anteriorly and
form
Nerve passes Bowman’s layer and
form

32. Nerve supply
Pericorneal plexus
Stromal plexus
Subepithelial
plexus
Intra epithelial plexus
LCN

33. Corneal layers in Slit section
Slit section of normal
cornea-
1. Tear film
2. Epithelium
3. Anterior stroma
4. Posterior stroma
5. Descemet’s
membrane and
endothelium

34. Corneal layers in Confocal biomicroscope
Superficial layer of corneal
epithelium
Basal cell layer of corneal
epithelium

35. Sub epithelial nerve plexus Shallow layer of stroma
containing polygonal
keratocytes and straight-
branching nerve fibers

36. Deep layer of stroma
containing keratocytes and
stout nonbranching nerve
fibers
Endothelium- hexagonal
and uniform size

37. Applied anatomy
Knowledge of anatomy of cornea and it’s layers is
important for diagnosis and management of many
diseases and as well as for many surgical techniques.
Such as-
1. Penetrating Keratoplasty
2. Superficial lamellar keratoplasty
3. Deep anterior lamellar keratoplasty(DALK)
4. Descemet striping endothelial keratoplasty(DESK)
5. Photorefractive keratectomy(PRK)
6. LASEK
7. LASIK

38. THANK YOU