Most of us have no idea where the cornea is, only that it is a part of the eye. The cornea is actually the first line of defense, along with the white of the eye (the sclera) against dirt, germs, and other potential causes of damage to the eye.
The cornea plays a key role in vision, refracting light that enters the eye. If your cornea is damaged by disease, infection, or an injury the resulting scars can affect your vision permanently. These are serious conditions that can cause clouding, distortion, scarring, and eventual blindness.
What is the Cornea?
Metaphorically, you can think of your eyes as cameras and the cornea as the glass protecting the lens. The cornea is the eye’s clear protective outer layer. It is made up of three layers:
- Epithelium — This outermost layer stops all kinds of stuff from getting into your eye. It also absorbs oxygen and nutrients from tears.
- Stroma — This is the middle and the thickest layer of the cornea. It is made up mostly of water and proteins, and it is solid but has elasticity.
- Endothelium — This is a thin layer, made up of just a single layer of cells on the back of the stroma. The endothelium works with aqueous humor, clear fluid in the front chamber of the eye, operating somewhat like a pump. If the stroma absorbs excess liquid the endothelium pulls it out. This keeps the stroma from becoming waterlogged, which would make the cornea opaque and hazy. This would impact your vision in the same way.
Corneal disease symptoms
Problems with the cornea often show themselves with redness around the cornea and/or corneal cloudiness. These are common symptoms:
- Visual impairment, such as blurred or cloudy vision
- Severe pain in the eye
- Sensitivity to light
- Headaches, nausea, fatigue
Who is at risk to develop a corneal disease?
There are certain risk factors that increase a person’s likelihood of developing a corneal disease:
- Normal aging can affect the health of the cornea
- Cataract or glaucoma surgery
- A family history (genetics)
- Wearing contact lenses
- Eye trauma
- Certain eye diseases and systemic diseases
What Conditions Could Affect The Cornea?
Corneal disease is a term that can indicate a number of different conditions that involve the cornea. There are three major types of corneal disease: keratoconus, Fuch’s endothelial dystrophy, and bullous keratopathy.
This disease causes the cornea to thin and change shape. This disease usually begins with blurring vision during the patient’s teenage years that progress during early adulthood. The cornea’s structure changes with keratoconus, protruding or becoming steeper. The curvature can create mild to severe distortion in the form of both astigmatism and nearsightedness. The disease can also cause swelling, scars on the cornea, and vision loss. Night vision severely deteriorates. The causes of keratoconus are usually genetic or from various eye diseases such as retinitis pigmentosa and others.
There are over 20 dystrophies that cause structural problems with the cornea. The most common is known as Fuchs’ endothelial dystrophy. This is an inherited condition that causes a slow breakdown of endothelial cells. Since the purpose of the endothelium is to pump fluids out of the cornea when this dystrophy causes the endothelium to break down, fluids do not get pumped out and the cornea swells. This causes the cornea to become cloudy and impact vision. Fuch’s dystrophy is passed down in the genes. It usually first shows signs in the person’s 30s or 40s but can take 20 years before it really affects vision.
When a person has bullous keratopathy the cornea becomes permanently swollen. This occurs when the endothelium is damaged and can no longer perform its job of pumping fluids out of the cornea. The cause of bullous keratopathy is usually tied to trauma, glaucoma, or inflammation after eye surgery. This condition formerly was a common complication of cataract surgery, but technology has improved to the degree this is now rare. Bullous keratopathy is now more likely related to glaucoma surgery.
What can cause bullous keratopathy?
Bullous keratopathy is a condition in which the cornea becomes permanently swollen. This occurs because the inner layer of the cornea, the endothelium, has been damaged and is not pumping fluid properly. We are born with a number and density of endothelial cells, and this gradually decreases over the course of our life. This is a normal decrease. Bullous keratopathy occurs due to an increased reduction in these cells.
Why does this happen? The likely causes have changed over the past 20 years. Formerly, bullous keratopathy was a relatively common complication of cataract surgery. That has changed as technology has improved both with the intraocular lenses implanted to replace the cataract-clouded natural lens and the techniques used in cataract surgery.
Now, the most common reason a person develops bullous keratopathy is as a complication of glaucoma surgery. These procedures can cause some cell loss in the endothelium. When this occurs, the normal pumping of excess fluid into the aqueous humor decreases. Now, this excess fluid moves forward into the stroma and epithelium, and this swells the cornea.
Another cause for bullous keratopathy can be congenital dystrophy of the endothelium, such as Fuchs’ dystrophy.
Diagnosing Corneal Diseases
When diagnosing corneal diseases Dr. Thom will review your medical and family history, as these diseases often have a genetic component. He then conducts an eye exam. He’ll check these areas:
- Eye refraction — Whether using a retinoscope or a phoropter, Dr. Thom will check your refraction errors.
- Slit-lamp examination — A vertical beam of light is directed onto the surface of your eye. Dr. Thom then examines the surface with a low-powered microscope. He is able to evaluate the shape of your cornea and can look for other issues, such as clouding.
- Keratometry — In this test, Dr. Thom focuses a circle of light on your cornea and then measures the reflection to determine the basic shape of your cornea.
- Computerized corneal mapping — These are special photographic tests that record images of your cornea to create a detailed shape map of the cornea’s surface. Corneal thickness can also be measured.
Corneal Disease Treatment Options
With early keratoconus, glasses or soft contact lenses can solve the problem. But the disease will progress. A procedure known as corneal crosslinking, where riboflavin eye drops are placed in the eye and the eye is then exposed to small amounts of UV light, can prevent keratoconus from worsening. A small number of people with keratoconus will need a cornea transplant. In these procedures, Dr. Thom replaces the damaged cornea with a donor cornea. This surgery is usually successful in stopping the cornea damage, but the patient will likely still need glasses or contacts for clear vision.
For Fuch’s dystrophy, treatments include eye drops/ointments, the patient drying his or her own swollen cornea with a hairdryer held at arm’s length two or three times daily, or a full or partial cornea transplant.
For bullous keratopathy, endothelial keratoplasty is usually the treatment method. This form of cornea transplant selectively replaces only the diseased layer of the cornea, leaving the other healthy areas intact.
Recovery After Treatment
Obviously, the use of eye drops or contact lenses/eyeglasses doesn’t create much of a recovery. But cornea transplants are a possible treatment option for just about every corneal disease. Most of these are partial thickness corneal transplants (known by the acronyms DSAEK, DMEK, or DALK).
After a partial thickness corneal transplant, the patient needs to lie on his or her back looking up at the ceiling for the first 48 hours, with the only exceptions being for eating and bathroom breaks. You’ll need to wear an eye shield overnight. After 48 hours, you can move about normally.
Your eye will feel irritated or scratchy for a few days, but you cannot rub it. Vision may be blurry for a period of time. It may take up to 12 weeks for your vision to fully recover.
You’ll use eyedrops as your eye heals. This helps prevent your body from rejecting your donated corneal tissue. Most patients can return to work or their normal routine from 1-2 weeks after surgery. Heavy lifting will need to wait for at least one month.
Do corneal scars fade?
The cornea is resilient. It usually heals after a minor abrasion, as new cells repair the damage. When the damage is more severe, a corneal scar can be left after initial healing occurs. Corneal scars will fade with time as the cornea heals itself. This does depend upon the depth and severity of the injury, as you would expect. If multiple layers have been damaged, the scar may take longer to fade, or it may never fade.
Can Corneal Disease Be Prevented?
Corneal diseases that have genetic components, such as Fuch’s dystrophy, cannot be prevented. The key here is an early diagnosis to prevent vision loss.
Other corneal infections and diseases are often the result of poor hygiene when wearing contact lenses. If you follow strict hygienic guidelines for contact lens use, this will dramatically lower your chances of developing corneal infections. For instance, even if your contact lenses have been approved to sleep in, this is a bad idea, and it greatly raises your chances of infection. It’s best to remove your lenses every night before going to bed.
Can a damaged cornea repair itself?
The cornea can repair itself after injury or some diseases. For instance, corneal lesions that are due to shingles usually heal themselves. But corneal dystrophies, diseases discussed here that cause structural problems with the cornea, will not repair themselves or heal without treatment.
What happens if I leave a corneal disease untreated?
If corneal diseases, such as keratoconus, are left untreated they will usually continue to worsen. This can lead to a gradual loss of vision.
Schedule Your Consultation Today
Call Dr. Thom to treat your corneal disease today! We are accepting patients at our Fargo, ND office.