Epithelium

The epithelium is the outermost layer of the cornea. The epithelium blocks the passage of foreign particles such as dust, water, and bacteria into the eye or other layers of the cornea. It also absorbs oxygen and cell nutrients from tears and then distributes these nutrients to the rest of the cornea. The epithelium is filled with thousands of tiny nerve endings, making the cornea extremely sensitive to pain when rubbed or scratched. The epithelium is a 5–6-layer structure with three types of cells: superficial cells, wing cells, and basal cells.

Bowman’s layer

Bowman’s layer is the transparent sheet of tissue lying directly below the basement membrane of the epithelium. It is composed of strong layered protein fibres called collagen. Once injured, the bowman’s layer can form a scar as it heals. Some vision loss can occur if these scars are large and centrally located.

Stroma

Stroma lies beneath the Bowman’s layer. It comprises 78 percent of water and 16 percent of collagen. Collagen gives the cornea strength, elasticity, and form. The collagen’s unique shape, arrangement, and spacing are important to produce the cornea’s light-conducting transparency.

Endothelium

The endothelium is extremely thin and the innermost layer of the cornea. Generally, there is a fluid inside the corneal layer and endothelium pumps this excess fluid out of the stroma. Without this pumping action, the stroma would swell with water and become hazy and opaque. A healthy eye requires a perfect balance between the fluid moving into the cornea and fluid being pumped out of the cornea. Once endothelium cells are destroyed by disease or trauma, they are lost forever. If too many endothelial cells are destroyed, corneal edema and blindness ensue, with corneal transplantation the only available therapy.

Function of Cornea

The main function of the cornea is the refraction of light and focusing. It also helps the eyes in two ways:

The cornea acts as a shield from germs, dust and other harmful substances. It shares the protective task with the eyelids, the eye socket, tears, and the sclera or the white part of the eye.
The cornea acts as the eye’s outermost lens. It functions like a window that controls and focuses the entry of light into the eyes. It also contributes between 75-80 per cent of the eye’s total focusing power.


When light strikes the cornea, it will bend the light onto the lens. Once the light passes through the lens, it refocuses the light onto the retina. The retina is a layer of light-sensing cells that line the back of the eye and starts the conversion of light into vision. The corneas also serve as a filter, screening out the ultraviolet wavelengths in sunlight. Without this protection, the lens and the retina would be highly susceptible to injury from UV radiation.

Tips for Healthy Cornea

Wash your Hands

Always wash your hands before touching your eyes as hands are a major source of bacteria, grit, pollen, and other irritants. Not washing hands may increase the risk of corneal injury or infection.

Rinse Out Irritants

If you get an irritant, rinse out with sterile eye drops or eye wash. If necessary, you can use a gentle stream of cool water from the tap across your eye, away from the unaffected eye.

Follow Vitamin-rich Diet

A diet rich in vitamins and minerals including vitamins A, C, and E helps to keep your eyes and corneas healthy. Green leafy vegetables and citrus fruits are good sources of these vitamins.