Cornea
The cornea is the clear, dome-shaped tissue at the front of the eye, covering the pupil and iris. If you wear contact lenses, they sit on top of the cornea.
Cornea structure
To better understand how corneal damage can affect your vision, it is important to understand the structure of the cornea itself. The cornea is comprised of various layers that perform different functions. The three major layers are:
- Corneal epithelium: The outermost layer of the cornea. It is a mere 5-7 cells thick and absorbs nutrients and oxygen from your tear film to nourish the rest of the cornea. The epithelial cells are constantly regenerated, so mild abrasions tend to heal quickly.
- Corneal stroma: The middle and thickest layer of the cornea. It is made of overlapping strands of connective tissue, called collagen fibrils. The uniform arrangement of the collagen is what makes the cornea clear. Scratches or damage that penetrate the stroma can lead to scars and diminish corneal transparency.
- Corneal endothelium: The innermost layer of corneal cells. These cells act as pumps and help remove excess moisture from the stroma, preventing cloudiness.
Corneal disease symptoms
Corneal disease is a broad term referring to any condition that affects the cornea, including infection, cellular degeneration or hereditary disorders. Left untreated, they may cause vision distortion or loss. The exact symptoms you experience will depend largely on the type of disease. In general, if you are experiencing any of the following symptoms, you should book an appointment with your eye doctor right away:
- Vision loss
- Blurry or clouded vision
- Eye pain or discomfort
- Redness
- Swelling
- Watery eyes
- Light sensitivity
- Overly dry eyes
During an eye exam, your eye doctor will be able to assess if your symptoms are related to your cornea and diagnose the problem. From there, he or she can find a treatment that is right for you.
Corneal conditions
Some common corneal diseases and conditions include:
- Corneal abrasions and scarring from injury or trauma.
- Infections: Ocular herpes is a condition caused by the herpes simplex virus, the same one that leads to cold sores. This infection leads to pain, watery eyes and inflammation. Herpes Zoster (shingles) can also cause sores to develop on your cornea. Bacterial and fungal infections can also affect your cornea; these are more common for contact lens wearers.
- Corneal ulcer: Corneal ulcers appear as open sores on your cornea. They can be caused by infection, injury, chemical damage and contact lens misuse. Without treatment, they may lead to permanent vision loss.
- Inflammation (keratitis): Keratitis is a broad term that refers to any inflammation of the cornea. It can be caused by injury, infections, allergies or eye dryness.
- Corneal swelling: Swelling can occur due to injury or infection. Another cause is bullous keratopathy, a condition that leads to permanent corneal swelling. This happens when the endothelium is damaged, preventing the cells from effectively pumping water out of the stroma and causing swelling.
- Dry eyes: Eye dryness occurs when your eyes can’t produce enough tears. Tears are important because they nourish the epithelium, keep your eye lubricated and help prevent abrasions. Without enough tears, you are more susceptible to injury, inflammation and infection. Dry eyes can be caused by certain medications, diseases like lupus and diabetes, environmental factors and lifestyle factors like screen time.
- Corneal dystrophy: Dystrophy refers to any degeneration of cells and tissue. One of the most common types of corneal dystrophy is Fuchs’ dystrophy, a condition in which the endothelium cells gradually deteriorate. Eventually, this leads to swelling and cloudy vision. Dystrophy can affect other parts of the cornea too. For instance, lattice dystrophy occurs when abnormal proteins disrupt the regular structure of the collagen fibrils of the stroma and may lead to corneal erosion.
- Corneal ectasia: Ectasia refers to a group of uncommon but serious eye disorders that cause your cornea to thin and change shape, distorting your vision. Keratoconus is a common type of corneal ectasia in which the cornea progressively protrudes forward into a cone shape. It can cause pain, visual distortions and light sensitivity.
Your treatment plan. Our eye care specialists can do whatever it takes to treat your cornea, from short-term solutions to more definitive repair. Your treatment plan will depend on the underlying disease and the extent of the problem. We often use multiple treatments simultaneously or in a staged process to achieve the best outcomes.
There are a few different treatments for the underlying causes of corneal disease. These include:
- Medications like antibiotics or antivirals to treat corneal infections.
- Surgery.
- Specialty contact lenses.
We are also experts at treating dry eye. Read more about dry eye and our treatments here.
Surgery
Collagen crosslinking for keratoconus and ectasia of the cornea
Keratoconus (see above) is a condition when the cornea becomes abnormally thin and bulges out like a cone, resulting in severe distortion of your vision. If caught early, we can perform a minimally-invasive procedure known as corneal collagen crosslinking (CXL). In CXL, riboflavin (vitamin B12) eye drops are applied to the cornea and activated by UV light. This leads to the formation of new collagen cross-linkages, strengthening your cornea and slowing the progression of keratoconus. Other treatments include the use of special contact lenses to improve vision (see below). In rare cases, a corneal transplant is needed.
Corneal transplant
In situations where corneal damage is irreparable, corneal transplantation is the only way to restore vision. In a corneal transplant, we remove all of your damaged cornea and replace it with a healthy, donated cornea. There are several types of transplants:
- Penetrating keratoplasty (PK): Our surgeon removes a full-thickness section of the central part of your damaged cornea, replacing it with a healthy cornea using sutures. Sutures may stay in place for up to a year, sometimes longer. You will likely need specialty contact lenses to achieve your best possible vision.
- Deep anterior lamellar keratoplasty (DALK): Our surgeon removes the stroma, and replaces it with a healthy one. Sutures secure the cornea in place. The healing process is similar to a PK.
- Endothelial keratoplasty: Partial corneal transplant, performed when the endothelial cells (cells on the innermost layer of the cornea) are damaged or dysfunctional. There are two main types:
- Descemet membrane endothelial keratoplasty (DMEK): Your surgeon removes the layer between the stroma and endothelium, called the Descemet’s membrane as well as your endothelium, and then replaces them with healthy donor tissue. The stroma remains untouched.
- Descemet-stripping automated endothelial keratoplasty (DSAEK): This is similar to DMEK, but your surgeon also removes a very small amount of your stroma and replaces it with a healthy section of stroma, Descemet’s membrane and endothelium.
Because transplants involve tissue from another patient, there is a risk of transplant rejection. Penetrating keratoplasty has the highest rate of rejection. Fortunately the rate is only 10 percent per year. Even if you have a rejection episode, most rejections can be treated medically as long as they are caught early. That’s why we will set up a thorough follow-up schedule with you.
In some cases, a corneal transplant is not possible. If you have had a failure of one or more corneal transplants, you may be a candidate for keratoprosthesis. A keratoprosthesis is an artificial cornea that can be used in some situations to restore vision.
Specialty contact lenses
Specialty contact lenses may be a solution for certain corneal conditions. It can be a non-surgical solution for patients who have keratoconus and other forms of corneal ectasia.
Similarly, you may need specialized contacts to help you heal from cornea transplant surgery. After treating the underlying problem with your cornea, we will customize contact lenses to help restore more of your vision.
These are specialty contact lenses only for specific corneal problems.
You’ll get a personalized treatment plan
Your eye care team will create a custom plan for your unique case. Don’t let an issue with your cornea(s) hold you back any more. Make an appointment today so you can get back to your extraordinary life.
Cornea care
Ronald E. Wise, MD, Ophthalmologist | UCHealth
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