If we think about the eye as a camera, the cornea would be the glass at the front of its lens. The cornea is a clear "window" through which light passes into the eye and provides most of the focusing power. Corneal injury, disease, or hereditary conditions can cause clouding, distortion, and scarring. Corneal clouding, similar to frost on a window-pane or dirty smudges on a camera lens, block the clear passage of light to the retina, reducing sight sometimes even to the point of blindness. Corneal injury and disease can sometimes be intensely painful.
What can cause corneal injury?
Nearly any foreign object can cause injury to the eye, especially the cornea, the most exposed part of the eye. Protection of the cornea is the reason emergency washing of the eye is absolutely necessary when the eye is exposed to toxic chemicals. Most corneal injuries are preventable with protective glasses and proper precautions when dealing with hazardous substances.
What causes corneal disease and degeneration?
Infections, whether bacterial, fungal, or viral are frequent causes of severe corneal damage and ulceration. Abnormal steepening of the cornea (keratoconus), degeneration occasionally following cataract surgery (corneal edema or swelling), and some aging processes can also affect the clarity and health of the cornea.
Some disorders of the cornea are inherited, and can lead to clouding and loss of sight.