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Corneal Disease
What is the Cornea?
The cornea is a thin, clear, spherical layer of tissue on the surface of the eye that provides a window for light to pass through. In a healthy eye, the cornea bends or refracts light rays so they focus precisely on the retina in the back of the eye.
There are many diseases that can affect the cornea, causing pain or loss of vision. Disease, infection or injury can cause the cornea to swell (called “edema”) or degrade (become cloudy and reduce vision).
Common Cornea Diseases and Disorders
- Allergies
- Bullous Keratopathy
- Conjunctivitis (“Pink Eye”)
- Dry Eye
- Corneal Dystrophies including Fuchs’ Dystrophy and Lattice Dystrophy
- Glaucoma (High Eye Pressure)
- Infections
- Keratitis (Viral Inflammation)
- Keratoconus
- Ocular Herpes
- Pterygium
- Shingles (Herpes Zoster)
- Stevens-Johnson Syndrome
Corneal Disease Treatment
Treatment for corneal disease can take many forms, depending on the underlying problem as well as the patient’s preferences. Some conditions resolve on their own and many can be treated with medication. If the cornea is severely damaged or if there is a risk of blindness, a corneal transplant may be recommended to preserve vision.
Corneal Transplant
The cornea is the clear covering of the front of the eye which bends, or refracts, light rays as they enter the eye. For clear vision to occur, the cornea must have the correct shape and clarity to focus incoming light rays precisely on the retina at the back of the eye. When the cornea becomes cloudy or misshapen from injury, infection or disease, transplantation may be recommended to replace it.
Corneal transplants are usually performed with local anesthesia so there is no pain. During the procedure, the cornea is replaced with one from a human donor. The new cornea carries little risk of rejection and can last for many years.
Phototherapeutic Keratectomy (PTK)
PTK is a laser surgical procedure that removes roughness or cloudiness from the cornea. The cornea is the smooth clear window of the eye in front of the colored iris that helps bend light rays so they focus directly on the retina, the light-sensing layer of cells at the back of the eye. If the corneal surface is rough or cloudy, the rays of light do not focus properly on the retina and images are blurry.
Until recently, a rough cornea was scraped smooth with a surgical blade, while a cloudy cornea required a partial or full corneal transplant. More recently, phototherapeutic keratectomy, or PTK, is an option.
The excimer laser allows some abnormal corneas to be treated with a cool beam of light that evaporates tissue. The principal advantage of laser surgery over conventional surgery is that the laser is able to create a smoother corneal surface than a blade while smaller amounts of tissue can be removed.
Potential complications after PTK include poor wound healing, excessive corneal flattening resulting in farsightedness, and irregular astigmatism or poor vision that cannot be corrected completely with glasses.
