Corneal Eye Disease

Despite the singular name, corneal eye disease is actually a group of medical conditions that produce complications in the eye's cornea, which is normally resilient. Although the diseases don't always lead to vision problems--at least initially--if left untreated, most eventually pose a significant danger to a person's ability to see properly.

The Cornea

• The cornea is a curved, transparent membrane that overlays the iris and pupil at the front of the eye. Comprised of proteins and cells, it has five layers with distinct functions: the epithelium (outermost layer that blocks foreign substances), Bowman's Layer (strong layer of collagen), the stroma (thick layer of water and collagen that determines the cornea's flexibility, shape and strength), Descemet's Membrane (strong, thin protective layer that combats injuries and infection), and the endothelium (innermost, thin layer that helps keep the cornea clear). Corneal eye diseases can affect any of the layers, damaging the curve of the cornea and, therefore, its ability to properly bend, or refract, light against the retina at the back of the eye, which creates impaired vision.

Allergies

• Most allergies that cause corneal problems are produced by pollen in the air, especially during dry or warm weather, as well as certain medications, some cosmetics such as mascara and wearing contact lenses. Symptoms include burning, itchy, red and teary eyes, although the condition rarely requires medical attention. Eyedrops containing an antihistamine are often sufficient to relieve symptoms.

Conjunctivitis

• Commonly called pink eye, conjunctivitis consists of several diseases that produce allergy-like symptoms in the conjunctiva, the tissue that lines the eye. The problem, which often causes no pain or vision impairment, frequently clears up independently. If it persists, however, medical attention is necessary to prevent it from spreading to and damaging the cornea.

Corneal Dystrophies

• Corneal dystrophies are a group of more than 20 separate diseases characterized by an accumulated cloudy substance in the cornea that causes eyesight to lose clarity. Symptoms and treatment of corneal dystrophies vary widely.
  The more common conditions include Fuchs' Dystrophy (the endothelial cells deteriorate slowly for no clear reason), Herpes Zoster (also called shingles, an infection caused by the same varicella-zoster virus responsible for chickenpox), Iridocorneal Endothelial Syndrome (corneal swelling combined with iris changes and glaucoma), Keratoconus (thinning cornea), Lattice Dystrophy (abnormal protein deposits in the stroma), Map-Dot-Fingerprint Dystrophy (abnormal epithelium lowest membrane), Ocular Herpes (recurring infection due to the herpes simplex virus), Pterygium (triangular, pink growths) and Stevens-Johnson Syndrome (blisters, holes, or inflammation).

Corneal Infections

• Bacteria and fungi can invade the cornea from a variety of sources, such as a foreign object entering the eye or wearing contaminated corrective lenses. If not treated promptly and properly, such infections can lead to inflammation and infections called keratitis, followed by eyesight damaged enough to necessitate a corneal transplant.

Dry Eye

• When the eye produces insufficient tears to keep the eye and its various components lubricated and protected against potential infections, the result is a scratchy, uncomfortable feeling. While artificial tears are adequate treatment for most sufferers, some eventually require a medical procedure to close the tear drains (openings in the eyelid that allow tears to leave the eye).