The Cornea

Stratified squamous and non-keratinized. It has 5-7 layers of cells

Anterior Epithelium

• Barrier to dust, bacteria, and fluid.

• Regenerates quickly if scratched.

• Has nerve endings → makes cornea very sensitive.

Anterior Epithelium

Thickness: ~8–14 μm.

Structure: Dense, acellular (no cells) sheet of collagen.

Bowman’s Layer

• Gives rigidity & shape to cornea.

• Once injured → doesn’t regenerate (forms a scar).

Bowman’s Layer

• Thickness: ~450–500 μm (about 90% of the cornea!).

• Structure: Collagen fibers + keratocytes (special cells).

Stroma

Functions:

• Maintains transparency because collagen fibers are arranged in a very regular, parallel way.

• Provides strength & thickness.

Stroma

• Thickness: ~8–12 μm (thickens with age).

• Structure: Basement membrane secreted by endothelial cells.

Descemet’s Membrane

Functions:

• Very elastic and strong.

• Protects against infections and injuries.

• Can regenerate if damaged.

Descemet’s Membrane

• Thickness: ~5 μm (single cell layer).

• Structure: One layer of hexagonal cells.

Endothelium

• Acts as a pump to keep cornea dehydrated (clear).

• Cells do not regenerate → if too many are lost (e.g., aging, surgery, disease), cornea swells and becomes cloudy.

Endothelium

• Location: Between the stroma and Descemet’s membrane.

• Thickness: Very thin → about 10–15 micrometers.

• Made of: Strong type of collagen tissue.

Duas Layer

• Adds strength to the cornea.

• Important in corneal surgeries (like deep anterior lamellar keratoplasty).

• Helps keep the cornea from swelling (acts as a barrier to fluid).

• ⚠ Clinical note:

  • Weakening/tears in this layer are linked to corneal hydrops (fluid buildup in keratoconus).

Duas Layer

Type of corneal opacity that is:

• Very faint opacity, almost like a thin mist on the cornea.

• Grayish, only slightly affects vision.

• Patient may still see well if it’s not in the visual axis.

Nebula

Type of corneal opacity that is:

• Moderate opacity.

• Gray or white spot, denser than nebula.

• Causes noticeable decrease in vision, especially if in the center.

Macula

Type of corneal opacity that is:

• Dense, white opacity (scar).

• Can cover part or the whole cornea.

• Severely reduces vision; if central, can cause blindness.

Leucoma