CONTACT LENS

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

9. THANKYOU