The document discusses the cornea, which is the transparent outer layer of the eye. It has five layers, with the stroma making up 90% of the corneal thickness and containing collagen that gives the cornea its structure and elasticity. The cornea focuses light onto the retina and acts as a protective barrier for the eye. One disease that can affect the cornea is keratoconus, where the cornea thins and bulges into a cone shape, causing vision problems. Keratoconus can be managed through contact lenses, collagen cross-linking treatment, corneal grafting, or corneal ring implants.
3. INTRODUCTION
It’s the outer most layer of the eye, domed shaped,
transparent tissue that covers the eyes.
It has about three quarters of the optical power of
the eye
its is inserted into the sclera at the limbus, its
about 540 micrometer thick centrally
4.
5. FACTS!!!
Did u know!!! the cornea is the mostly densely
innervated tissues in the body!!
Supplied by the first branch of trigeminal nerve
It has no blood vessels although its alive, it
receives all the nutrients from the aqueous humor
(posteriorly) and tears (anteriorly).
6. Cornea transparency is due to;
Uniform structure
A vascularity
Deturgescence (relative dehydration)
7. cornea has five layers ;
i) The epithelium;
Is stratified squamous and non keratinized
It has nerve endings
acts as a barrier of the eye to the foreign material
eg dust.
It absorb oxygen and nutrients form tears
8. ii) Bowman’s membrane
Its formed by collagen fibres, when injured it forms
scar as it heals, if the scar will form centrally the
there will be visual loss.
9. iii) The stroma
It contribute to about 90% of the corneal thickness.
Its mainly water and collagens, collagens are the
ones which gives the cornea its structure and
elasticity.
The stoma can scar but can not regenerate.
11. v) The endothelium
It maintain corneal deturgescence by pumping
excess fluid out of the stoma, failure of
endothelium to do its work can lead to cornea
edema
Its cells cannot regenerate.
There is loss of cells in this layer as the age
increases
13. FUNCTION OF THE CORNEA
It helps in focusing the light that come into the eye
so as it can fall on the retina.
It’s a physical barrier together with tears and eyelid
against the dirty and germs that come into contact
with the eye.
It also protect the eye against the UV light from the
sun.
14. The cornea can be affected by different diseases,
keratoconus being among them
15. KERATOCONUS
It’s a disease characterized by progressive thinning
of the cornea and takes a cone shape which results
to astigmatism (the cornea cannot focus the light
to the retina).
Most of refraction of light occurs at the air –cornea
interface so change in the cornea shape can lead to
major impact on vision.
16. Signs
Bulging of the lower eyelid on down
gazing(munson sign)
Oil droplets reflex on direct ophthalmoscope
Scissors reflex on retinoscopy
Stromal scarring this occurs when descement’s
membrane has rupture
17. Some research suggest that its due to imbalance of
enzymes in the cornea which leads to oxidative
damages leads to weakening and bulging of the
cornea.
Overexposure to the ultraviolet light,
Excessive rubbing of the eye ,
Poor fitted contact lens
Genetic predisposition.
CAUSES OF KERATOCONUS
18. Can glasses correct the keratoconus?
Glasses can only correct the regular astigmatism but
as for keratoconus it is an irregular astigmatism.
Contact lenses can be used to make the air –cornea
interface more spherical so as the light can focus to
the eye.
19. MANAGEMENT OPTIONS
Contact lenses
Collagens cross linking; it prevent the progression of
early form of the disease (riboflavin eye drops which
is then exposed to the sun light)
Corneal graft
Corneal ring segment implant