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 the 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.
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 progresses 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.
- Fuchs’ endothelial dystrophy
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.
- Bullous keratopathy
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.
How Are Corneal Diseases Diagnosed?
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 surface. Cornea thickness can also be measured.
How Do You Treat Corneal Disease?
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 eyedrops 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 eyedrops/ointments, the patient drying his or her own swollen cornea with a hair dryer held at arm’s length two or three time 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. These help prevent your body from rejecting your donated corneal tissue. Most patients can return to work or their normal routine in from 1-2 weeks after surgery. Heavy lifting will need to wait for at least one month.
Preventing Corneal Disease
Corneal diseases that have genetic components, such as Fuch’s dystrophy, cannot be prevented. The key here is early diagnosis to prevent vision loss.
Other corneal infections and diseases are often the results 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.
Call Dr. Thom to treat your corneal disease today! We are accepting patients at our Fargo, ND office.