Corneal Disease
In order to provide clear vision, the cornea must be transparent. This tough connective tissue is the most important refractive surface of the eye and does more to focus the entering rays of light than any other part of the eyes. For this reason, any defect or opacity in the cornea will have a profound effect on vision. In addition, the cornea has many nerve endings and even the slightest scratch can be extremely painful. The cornea maintains its integrity through different means, one of which is the constant flow of tears, which spreads over the eye through eyelid blinking. Any condition that decreases the amount of tears or decreases the eyelid action will cause drying, discomfort and clouding of the cornea. Approximately 6 percent of blindness in the United States is caused by injury of diseases involving the cornea.
The most common symptoms of cornea disease include the following:
- Blurring of vision with a diffuse cloudy appearance.
- Multiple images seen when only one eye is open.
- Burning and irritation of the eye.
- A foreign body sensation as if a small piece of sand or other particle is felt underneath the eyelid.
Common conditions of the cornea include:
Corneal ulcers - usually caused by bacterial infections, most commonly from contaminated contact lenses
Viral infections - which can cause significant scarring and vision loss
Keratoconus - which is a condition where the shape of the cornea becomes warped. Usually special contact lenses can help correct the vision, but sometimes corneal transplantation is needed.
Pterygium - which is a common condition where the conjunctiva (the “white skin”) of the eye starts to grow over the cornea. This can be cosmetically unpleasant, as well as cause eye irritation, redness, and blurred vision. It is caused by sun and wind exposure. This is treated by surgically peeling off the overgrowth. The surgery very commonly done and is very successful.
One of the advantages in examining and treating the cornea is its accessibility for examination. It is easily examined with a slit lamp biomicroscope. There are also additional instruments used in examining the cornea, such as a keratometer, which measures the curvature of the anterior surface of the cornea, and a specular microscope. This instrument is designed to see the endothelial cells lining the posterior surface of the cornea.
There are various types of corneal diseases and corneal conditions with many modalities of therapy. Treatment can involve the use of teardrops, antibiotics, steroid drugs, antiviral drops, soft contact lenses and surgery. When the cornea is significantly scarred, the only treatment is a cornea transplant.
