What is the Cornea?
The cornea is the clear, outermost layer of the eye and can be described as resembling a
window into the interior of the eye.
What is the Cornea’s Function?
The main function of the cornea is to allow light to pass into the interior of the eye, so that it
can reach the lens and then the retina. Other functions include protecting the eye from dust,
germs and other harmful substances, as well as providing focus and regulating light coming
into the eye in conjunction with the lens.
What is the Structure of the Cornea?
The cornea is made up of five distinct layers:
- Epithelium: The outermost layer.
- Bowman’s Layer: A transparent sheet made of collagen.
- Stroma: Composed of 78 percent water and 16 percent collagen. This additional
collagen gives strength, elasticity, and form.
- Descement’s Membrane: The fourth layer which is comprised of different collagen
than the stroma layer.
- Endothelium: The innermost layer. This regulates excess fluid out of the
What is Corneal Disease?
Corneal disease is a serious condition affecting the cornea that can cause clouding,
vision distortion and eventual blindness. The cornea is like the clear front window of
the eye that transmits light to the interior of the eye and allows us to see clearly. There
are many types of corneal disease. The three major types are keratoconus, Fuchs’
endothelial dystrophy and bullous keratopathy.
Keratoconus is a weakening and thinning of the central cornea. The cornea develops a
cone-shaped deformity at a pace that can be rapid, gradual or intermittent.
Keratoconus usually occurs in both eyes, but can occur in only one eye.
Fuchs’ endothelial dystrophy is a hereditary abnormality of the inner cell layer of the
cornea called the endothelium. In a healthy eye, this layer pumps fluids out of the
cornea, keeping it thin and crystal clear. An unhealthy endothelium does not properly
pump fluids causing the cornea to swell and become cloudy which decreases vision.
Bullous keratopathy is a condition in which the cornea becomes permanently
swollen. Damage to the inner layer of the cornea, the endothelium, causes a buildup of
excess fluid in corneal tissue.
What are the symptoms of corneal disease?
The exact symptoms of corneal disease often depend on the type. When the cornea
protrudes or steepens (keratoconus), vision becomes increasingly blurred and contact
lens wear, which is often an early treatment for the disease, becomes difficult. The
irregular shape of the cornea makes it difficult for the contact to stay on the eye. Fuchs’
endothelial dystrophy and bullous keratopathy may cause glare at night or in bright
sunlight. As these conditions progress, vision may become foggy or blurry in the
morning but improve as the day goes on. As the disease worsens, vision stays blurry
later into the day or may not clear up at all. Corneal diseases can be very painful.
If you are experiencing one or more of these symptoms, contact Tomoka Eye
Associates Cornea Specialist Dr. Rory Myer, to set up an appointment.
What causes corneal disease?
Corneal disease may be caused by one or more of the following factors
- Bacterial, fungal or viral infections are common causes of corneal damage
- The aging process can affect the clarity and health of the cornea
- Bullous keratopathy occurs in a very small percentage of patients following cataract
or intraocular lens implant surgeries
- Heredity / Genetics
- Contact lens use
- Eye trauma
- Certain eye diseases, such as retinitis pigmentosa, retinopathy of prematurity, and
- Systemic diseases, such as Leber’s congenital amaurosis, Ehlers-Danlos syndrome,
Down syndrome and osteogenesis imperfecta
How is corneal disease diagnosed?
Using a slit lamp and advanced diagnostic technology such as corneal topography, Dr.
Myer can detect early cataracts, corneal scars, and other problems associated with the
front structures of the eye. After dilating your eyes, Dr. Myer will also examine your
retina for early signs of disease – including certain corneal diseases.
How is corneal disease treated?
As with any serious eye infection, corneal disease should be treated immediately.
Although corneal transplant is almost always the necessary treatment to restore vision
when the cornea becomes clouded, there are other measures that can be taken to
prolong vision in the early stages of disease such as special contact lenses or
To catch and treat corneal disease early, schedule regular eye exams at Tomoka Eye
Associates to protect your vision.
A corneal infection can often result from an eye injury, trauma or other forms of eye damage.
Contact lens wearers are susceptible, as the lens rubs on the cornea which could lead to slight
damage to the epithelium, allowing bacteria to enter. Proper hand hygiene before handling
contacts can reduce the risk of bacteria infecting the eye.
Melting ulcers can be caused by Pseudomonas bacteria that break down the stroma or
supportive tissue of the cornea. The breakdown of these fibers can also lead to corneal
perforation (a hole in the cornea).