The document summarizes key differences between the sclera and cornea, the outer coverings of the eye. It notes that both are connective tissues containing collagen fibrils. The cornea is uniquely transparent due to the arrangement of collagen fibrils. It has 5 layers - epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium. The stroma is the thickest layer and contains parallel collagen fibrils. The sclera is opaque and thicker than the cornea, protecting the eye from increased pressure. It lies behind the cornea and aqueous humor.

1. Sclera and Cornea
Group members
Abenezer Bogale
Arsema Beshewa
Bamlak Cherinet

2. Introduction
• Both of them make up the outer covering of the
eye
• They are connective tissues containing collagen
fibrils embedded in proteoglycan rich extra-
fibrilar matrix
• Strong structures because of the deposition of
collagen in lamellar structure
• The both protect the eye from increased pressure
within and mechanical insult from outside

4. Cornea
• It is uniquely transparent
• The transparency is because of the coneal
collagen fibrils' arrangement in which they are
positioned in uniform diameter with respect to
eachother in a lateral fashion
• The main refractive element of the eye
• It is the part of the eye anterior to the aqueous
humor
"Cornu", Latin, horn

5. Cornea cont.
• No blood supply- gets metabolites by diffusion
• 5 layers
– Epithelium
– Bowman's layer
– Stroma
– Descmet's membrane
– Endothelium

6. Cont…
Epithelium
It is a protective layer against foreign material and
gives some mechanical support
It consist upto 10 cell layer with non stratified
squamous non kerstinized morphology
Bowmans layer
It has a dense accumulation of collagen fibrils that are
tightly interwoven
It is only 10 micrometers thick

7. Cont...
Stroma
It is about 800 micrometers thick
It is composed of distinct lamellae composed of
parallel arranged tightly packed and very regularly spaced
collagen fibrils
Descment membrane
It is 10 upto 20 micrometer thick
It increases during life time
It is composed of collagen type IV and glycoprotein

8. Cont...
Endothelium
It prevents uncontrolled entrance of foreign
substances including water
It dehydrates water from stroma through water
pumps

10. Sclera
It comes from Greek word hard
It is opaque and it is whitish from outside
It is covered by translucent membrane of
conjunctiva
It is 1 millimeter

11. Thank you