The cornea is the transparent outer layer of the eye that acts as a major refracting medium and protects the internal structures. It has multiple layers including an epithelium, endothelium, and stroma. The cornea maintains transparency through the uniform arrangement of its cells, high water content, and fluid transport mechanisms in the endothelium like sodium-potassium pumps. Nutrients enter the cornea by diffusion and oxygen comes from the tear film to support the metabolic activities of the epithelium and endothelium layers.

1. PHYSIOLOGY OF CORNEA

2. CORNEA
• Cornea is transparent, avascular, structure.
• Anterior one sixth of the outer fibrous coat of
eyeball.
• Total power of cornea:+43D

3. LAYERS OF CORNEA

4. CORNEAL PHYSIOLOGY
Primary functions:
• Act as major refracting medium
• Protect the intraocular contents
Secondary functions:
• Absorption of topically applied drugs
• Wound repair
• Maintain transparency and replacement of tissue

5. CORNEAL TRANSPARENCY
Anatomical factors :
• Uniform and regular arrangement of corneal epithelium
• Peculiar arrangement of corneal lamella
• Corneal avascularity
• Optically smooth tear film
• Absence of myelin sheath around corneal nerves

6. Physiological factors:
• Highest water content than other connective tissues in the body
• Act as barrier function of limiting layers : Endothelium
Epithelium
• Corneal endothelium Plays role in controlling fluid transport due to
several enzymes.
Na+/K+ ATP ase pump
Na+/H+ pump
Bicarbonate dependant ATP ase
Carbonic anhydrase enzyme system

7. • Evaporation of water from corneal surface
• Stromal swelling pressure
• Corneal crystalline such as water soluble proteins of keratocytes
contribute the corneal transparency

8. METABOLISM OF CORNEA
• Endothelium and epithelium are the active are active metabolizing layers
Source of nutrients:
• Solutes(glucose and others)enter the cornea by either simple diffusion or
active transport.
• Oxygen is derived directly from air through the tear film
• Endothelium requires oxygen and glucose for metabolic activities
• Energy in the form of ATP

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