The Cornea: The Outer Shell Protector of the Eye

Close up shot of retina and cornea for St. Charles Vision in New Orleans, LA

When you consider your eyes, you may not immediately think of your cornea—after all, despite the fact that it’s the outermost layer of your eye, it’s completely transparent—but it plays a critical role in your overall eye health. In many ways, the cornea is to the eye what the shell is to a turtle — the protective shield. Here’s how it works, and why it’s so important to your vision.

The cornea is composed of multiple layers, each with its own purpose:

  • Epithelium: As the outermost layer, the epithelium acts as a shield to the other parts of the eye, blocking bacteria, dust, and other foreign objects from getting inside. What’s more, it also works to absorb oxygen and other nutrients, which it then distributes to the underlying layers. You may not be aware of it on a day-to-day basis, but the epithelium is actually capable of sensation: the millions of nerve endings found here alert the brain whenever the eye is touched—which is why you can sometimes sense the presence of contact lenses or feel pressure when you rub your eyes!
  • Bowman’s layer: Located underneath the epithelium, this membrane is composed mainly of collagen fibers, which can help with scarring if the eye is ever injured. So, if you happen to fall off your bicycle and injure your eye, the Bowman’s layer will play a major role in the healing process.
  • Stroma: The thickest part of the cornea, the stroma is found just under the Bowman’s membrane. Like the membrane above, the stroma is composed of water and collagen. This gives it a particular elasticity, which is an essential part of the cornea’s light-conducting transparency—which without, we literally could not see anything but darkness, and that’d be quite scary!
  • Descemet’s membrane: Beneath the stroma is a thin but strong layer of tissue known as Descemet’s membrane. Like the epithelium, this membrane works to keep out any bacteria or foreign object that has made it that far. If someone accidentally sneezes nearby and the germs make their way into your eye, the Descemet’s membrane will take care of it.
  • Endothelium: As the final layer of the cornea, this thin layer plays an important role in keeping the dome transparent, allowing light to come through. Composed of a “pumping station” of cells, it keeps an even balance of liquid in the stroma and the rest of the eyeball. Without it, the stroma would swell and become opaque, keeping light from entering. Essentially, blindness would be inevitable for all without this final layer of the cornea.

With so many layers dedicated to healing from injuries, as well as shielding the eye from damage and foreign materials, the cornea is truly the protector of your eyes—so be sure to keep it healthy by eating nutrient-rich foods and wearing protective eyewear!