brief anatomy of cornea with its layers, structures, vascularity etc has been delt here

1. Diseases of cornea
• Contents
1. Applied anatomy
2. Applied physiology
3. Congenital anomalies of cornea
4. Inflammatory conditions of cornea
5. Corneal degenerations
6. Corneal dystrophies
7. Ectatic conditions of cornea
8. Corneal transparency abnormalities
9. Corneal surgeries

2. Applied anatomy of Cornea
• Transparent
• Avascular
• Watch glass like structure

3. Three Coats of Eye Ball
1.OUTER COAT
2.MIDDLE COAT
3.INNER COAT

4. OUTER COAT
Tough Fibrous Coat
Ant 1/6th of Globe
Transparent
Cornea
Radius---8mm

5. Outer Coat
Tough Fibrous Coat
Post 5/6th of Globe
White & Opaque
Sclera
Radius---12mm

6. Corneoscleral Limbus
Junction of Cornea and Sclera
Contains
1.Trabecular Meshwork
2.Canal of Schlemn

7. DIMENTIONS
Size of Cornea
ANTERIOR SURFACE
Verticle- dia. 10.6 mm
(11mm)
Horizontal- 11.7 mm to
12mm
Posterior surface- circular
H.Diameter- 11.5 mm
V.D- 11.5mm

8. Thickness
Central portion- 0.52 mm
Peripheral portion- 1 mm

9. Radius of curvature

10. • Refractive index- 1.376
• Refractive power-
1. Cornea - 45 D- ¾th of total eye
2. Total eye - 60 D

11. Predescemet’s
membrane

12. Layers of cornea
From Anterior to Posterior{EBS PrDE}
1. Epithelium
2. Bowman’s Zone
3. Stroma(substantia propria)
4. Pre Descemet,s Membrane(Dua’s)
5. Descemet Membrane
6. Endothelium

13. THE CORNEAL EPITHELIUM
• This outer layer of the cornea is five to seven
cells thick and measures about 50 microns
• — making it slightly less than 10 percent of
the thickness of the entire cornea.
• Epithelial cells are constantly being produced
and sloughed off in the tear layer of the
surface of the eye.
• The turnover time for the entire corneal
epithelium is about one week.

14. Bowman's layer.
• This is a very thin (8 to 14 microns) and
• dense fibrous sheet of connective tissue
• that forms the transition between the corneal
epithelium and the underlying stroma.

15. corneal stroma.
• This middle layer of the cornea
• approximately 500 microns thick,
• or about 90 percent of the thickness of the overall
cornea.
• It is composed of strands of connective tissue called
collagen fibrils.
• These fibrils are uniform in size and are arranged parallel
to the cornea surface in 200 to 300 flat bundles called
lamellae that extend across the entire cornea.
• The regular arrangement and uniform spacing of these
lamellae is what enables the cornea to be perfectly clear.

16. Descemet's membrane.
• This very thin layer separates the stroma from
the underlying endothelial layer of the cornea.
• Descemet's (pronounced "DESS-eh-mays")
membrane
• gradually thickens throughout life — it's about 5
microns thick in children
• 15 microns thick in older adults.

17. The corneal endothelium.
• This is the innermost layer of the cornea.
• The back of the endothelium is bathed in the
clear aqueous humor that fills the space between
the cornea and the iris and pupil.
• The corneal endothelium is only a single layer of
cells thick and measures about 5 microns.
• Most of the endothelial cells are hexagonal (six-
sided), but some may have five or seven sides.
• The regular arrangement of these cells is
sometimes called the endothelial mosaic.

18. Cornea Function
• As already mentioned, the clear cornea allows
light to enter the eye for vision.
• But it has another very important function as
well — the cornea provides approximately 65 to
75 percent of the focusing power of the eye.
• The remainder of the focusing power of the eye is
provided by the crystalline lens, located directly
behind the pupil.
• In addition to allowing light to enter the eye and
providing most of the focusing power of the eye,

19. • individual parts of the cornea have specialized functions:
• corneal stroma typically leave permanent scars that can
affect vision.
• Corneal endothelium.-corneal epithelium provides an
optimal surface for the tear film to spread across the
surface of the eye to keep it moist and healthy and to
maintain clear, stable vision.
• Bowman's layer. The dense nature of Bowman's layer helps
prevent corneal scratches from penetrating into the corneal
stroma.
• Corneal abrasions that are limited to the outer epithelial
layer generally heal without scarring; but scratches that
penetrate Bowman's layer

20. Epithelium
• 50-60 µm thick- 5to 7 layers
• Statified squamous subtype
• Covers the stroma anteriorly
• Continuous with epithelium of bulbar conjunctiva
• Life of epithelial cells is 7 days
• Prevent aqueous solutions to penetrate
• Functions- provides smooth refractive surface
• - heals without leading to scar formation

21. -flat
-polygonal
-columnar

22. Bowman’s membrane
• Consists of acellular mass of codensed
collagen fibrils
• Thickness- 12µm
• It shows considerable resistance to infections
• Once destroyed cant be regenerated
• Heals with scaring

23. Stroma
• thickness-500µm
• 90% of the corneal thickness
• Composed of collagen fibrils arranged in lamellar
form
2 zones
• Bowman Zone
• Lamellar Stroma
Once deformed its typical structure is not restored

24. • Dua’s Membrane- Pre Descemets
• Discovered in 2013 by Dr. Herminder Dua, indian
ophtomologist working in great britain
• Thickness- 15 µm
• Thick,acellular, very strong
• Impervious to air

25. • Descemets membrane-
• Posterior elastic lamina
• Strong homogenous basement membrane
• Very resistant to chemical agents, trauma, pathological
process
• Hence, Descemetocele can maintain integrity of cornea foe
long duration
• can regenerate
• When torn,remains in state of tension, curls inward on
itself
• membraneDescemet membrane

26. Endothelium
• Single layer of flat polygonal epithelial cells
• On Slit Lamp Biomicroscopy appears as a
mosaic.
• Cells are tightly bound together
• Never regenerates
• Contain Active Pump Mechanism which keeps
cornea dehydrated

27. Blood supply
• Central cornea is avascular
• Corneoscleral limbus is generously supplied by
anterior conjuntival branches of the anterior
ciliary arteries
• Aqueous humor and tear film provides
nutrients

28. Nerve Supply
• Supplied by sensory and autonomic nerves
• Sensory-Branches of the ophthalmic division of trigeminal
nerve
• Autonomic- sympathetic fibers arising from ciliary ganglion
• Most are concentrated in the anterior stroma beneath the
Bowman zone and send branches forward into epithelium
• After going about 2mm in cornea the nerves lose their myelin
sheath and divide dichotomously
• And forms 3 plexus – stromal, subepithelial , intra epithelial
• Descemet membrane and endothelium are not innervated

29. Page 21

30. Applied physiology
• Acts as major refracting media
• Protects intraocular structures
• Performs these functions by-
• A] maintaining of its transperency
• B] regular replacement of its tissues

31. Transparency
1. Avascularity of cornea
2. Relative State of relative dehydration
3. Absence of myelinated nerve fibres
4. Arrangement of collagen fibrils in stroma-
• 1. Lattice Theory Of Morice- regular lattice arrangement of collagen fibrils
• 2. Goldman Theory Of Minimal Seperation Of Collagen Fibrils – presence
of small diameter collagen fibrils with small seperation, which will not
cause scattering of light
5. Peculiar refractive index- <200µm
6. Swelling pressure
7. Corneal crystallins
• Also due to,Tight junctions of the epithelial cells
• Endothelial pump mechanism
• Absence of blood vessels
• Absence of pigments
• Scarcity of cell nuclei in stroma
• Regular structure of stroma

32. The end