The Cornea

✅Anatomy of the Cornea:

• 11.5 mm horizontal diameter
• 10.5 mm vertical diameter
• 1 mm thick periphery
• 0.5 mm thick centrally
• Anterior surface radius 7.7 mm
• Posterior surface radius 6.8 mm

✍️ Epithelium

• Stratified squamous, nonkeratinized, nonsecretory epithelium (keyword)

• 5–6 layers 

• Superficial cells have microvilli (needs
tears to keep cornea smooth)

• Basement membrane (strongly attached
to Bowman’s layer )

✍️ Bowman’s layer

• 8-12 μm

• Acellular

• type IV collagen 

•Don’t regenerate , replaced by fibrous tissue if damaged (scars)

• Ends abruptly at limbus

✍️ Stroma (substantial propia)

• 90% of cornea thickness, 400 μm centrally

• 80% water

• Glycosaminoglycans in extracellular matrix

– Keratan sulphate (50%)
– Chondroitin phosphate (25%)
– Chondroitin sulphate (25%)

• posterior condensation of the stroma is newly called ( Dua layer) 

✍️ Descemet’s membrane

• Basement membrane of the endothelium
(keyword)

• 10 μm thick

• Secreted and regenerated by endothelial cells

• Type IV collagen 

• Hassall-Henle bodies( peripheral)

• Terminates abruptly at limbus (Schwalbe’s
line)

✍️ Endothelium

• Single layer, polygonal, cuboidal cells

• Tight junctions (control of corneal hydration)

• Microvilli

• Don’t regenerate 

• Repair occurs by cellular hypertrophy ( polymegacism)and sliding(polymorphism)

• Line passages of trabecular meshwork

✅ Physiology of Cornea:

• Light transmission (400–700 nm light)

• Light refraction:

• 43 D (70% of eye’s refractive power)

• Refractive index of cornea 1.376

• Protective function to the globe 

• Cornea obtains glucose mainly from aqueous but tears and limbal capillaries appear to provide
minimal contribution

• Glucose can be stored in epithelium as glycogen

• ATP obtained by glycolysis and Kreb’s cycle 

• oxygen from aqueous or from either capillaries at the limbus or precorneal film

✅ The Cornea Transparency due to :

• Relative dehydration of cornea by endothelium and epithelium

• Endothelial pump removes fluids from stroma

• Evaporation of water from tear increases
osmolarity of tear, which draws water from cornea

• Normal intraocular pressure (if too high, relative hydration occurs)

• Relative acellularity, lack of blood vessels and pigments

• Regular matrix structure of corneal fibrils

• Destructive interference of light occurs

• Consistent refractive index of all layers

✅ Nerve Supply in The Cornea:

• 5th CN ( ophthalmic division)

• Long posterior ciliary nerves gives 3 plexuses 

– Annular plexus at limbus

– Subepithelial plexus just below Bowman’s membrane

– Intraepithelial plexus

• Nerves loss it’s myelin just after entering the cornea.

The cornea power point presentations:

Anatomy of cornea

1. Introduction CORNEA – Medieval Latin “ co rne a te la “ HORNY WEB (latin ,cornu = horn)  Transparent avascular tissue with a convex anterior surface & concave posterior surface.  Main function is OPTICAL  Accounts for 70% of the total refractive power of the eye (+ 43D)  Other functions are: -STRUCTURAL INTEGRITTY -PROTECTION FOR
2. DIMENSIONS  Anterior Surface : Vertical – 11.7 mm Horizontal – 10.6 mm  Posterior Surface : Both 11.7 mm  Thickness : Central 0.52 mm Peripheral 0.67 mm  Surface Area: 1.3 cm2
3. Radius of Curvature Anterior – 7.8 mm Central 1/3 Posterior – 6.5 mm – Peripheral cornea is more flattened  Topography Anterior curvature is spherical in 2-4 mm zone decentered upwards & outwards relative to visual axis but centered to the pupillary aperture( lies 0.4 mm temporally) — CORNEAL CAPorAPEX  Curvature varies from apex to limbus , greater
4. STRUCTURES 5 LAYERS A nterior Epithelium Bowman’s layer C entral stroma Descemets membrane Endothelium.

Anatomy & physiology of cornea

The Cornea Videos :

Cornea : 1. anatomy

The cornea