What is the cornea?
The cornea is the clear tissue at the front and center of the eye. Its transparency permits light to pass into the eye, through the pupil, lens, and onto the retina at the back of the eye. The three major layers that compose the cornea are the outer layer or epithelial layer, the middle layer termed the stroma, and finally a single layer of cells called the endothelium.
The curvature of the cornea plays an important role in focusing (refracting or bending) light. The normal cornea is smooth, clear, and tough. It helps protect the eye from infection, dust, and other foreign material.
What are the different types of corneal disease?
There are several conditions that can affect the cornea, including the following examples:
- Bacterial, fungal, or viral keratitis, as well as parasitic diseases
- Abrasions or exposure to toxic chemicals
- Corneal dystrophies and degenerations
- Fuchs' dystrophy and keratoconus
- Autoimmune disorders
- Wegener's disease, rheumatoid arthritis, or lupus
- Nutritional deficiencies
- Vernal and atopic keratoconjunctivitis
- Pterygium or benign or malignant cancerous growths on the eye's surface
The cornea can also be damaged secondarily by other eye conditions such as tear film abnormalities (dry eye), eyelid disorders, and glaucoma.
What are the signs and symptoms of corneal disease?
Signs of corneal disease can include redness around the cornea and/or cloudiness within the cornea. Symptoms include
- blurred or cloudy vision,
- sensitivity to light.
Blurred vision may be the result of an irregular tear layer or epithelial layer (as seen in dry eye), scarring (following trauma or infection), deformity of the corneal curvature (as seen in keratoconus), or swelling of the cornea (as seen in Fuchs' dystrophy). Pain and light sensitivity can be quite severe, especially in conditions affecting the outermost layer (epithelium) of the cornea. Examples include traumatic abrasions, infectious ulcers, and erosions from dryness.