- Causes & Risk Factors
- Signs & Symptoms
What is the cornea?
The cornea is the clear tissue at the front and center of the eye. Its transparency permits light to pass into the eye, through the pupil, lens, and onto the retina at the back of the eye. The three major corneal layers are the outer layer of the cornea or epithelial layer, the middle layer termed the stroma, and finally, a single layer of cells called the endothelium.
The curvature of the cornea plays an important role in focusing (refracting or bending) light. The normal cornea is smooth, clear, and tough. It helps protect the eye from infection and foreign material.
What are the different types of corneal disease?
There are several common causes of corneal disease, including the following:
- Bacterial, fungal, or viral keratitis, as well as parasitic diseases
- Abrasions or exposure to toxic chemicals
- Dystrophies and degenerative corneal disorders
- Fuchs' dystrophy, map-dot-fingerprint dystrophy, or lattice corneal dystrophy
- Autoimmune disorders
- Wegener's disease, rheumatoid arthritis, or lupus
- Nutritional deficiencies
- Vitamin A deficiency
- Vernal and atopic keratoconjunctivitis
- Pterygium or benign or malignant cancerous growths on the eye's surface
- Ectasia (thinning)
- Keratoconus, or thinning of the cornea following refractive laser surgery
- Stevens-Johnson syndrome is a rare but serious inflammatory reaction to a medication or an infection
The cornea can also be damaged secondarily by other common eye conditions such as tear film abnormalities (dry eye), eyelid disorders, glaucoma, and iridocorneal endothelial syndrome (ICE), which may be associated with glaucoma.
What are the causes and risk factors of corneal disease?
The causes of corneal disease vary widely. The conditions listed above are due to hereditary (inherited) causes, infection, trauma, autoimmune disorders, nutritional deficiencies, allergy, secondary causes (other eye diseases that also affect the cornea), growths, and tumors among others.
Risk factors similarly vary depending on the individual's circumstances. Some risk factors are not modifiable, such as inherited genetic conditions. Others might be avoidable by limiting exposure to trauma and infection. In many people, prompt treatment of corneal disease in its early stages will minimize the severity of the disease and its complications.
What are the signs and symptoms of corneal disease?
Signs of corneal problems can include redness around the cornea and/or corneal cloudiness.
Symptoms include the following:
- visual impairment, such as blurred or cloudy vision,
- severe pain in the eye,
- tearing, and
- sensitivity to light.
- Some patients have additional symptoms of headache, nausea, and fatigue.
Blurred vision may be the result of an irregular tear layer or epithelial layer (as seen in the dry eye), scarring (following trauma or infection), cataracts, deformity of the corneal curvature (as seen in keratoconus), or swelling of the cornea (as seen in Fuchs' dystrophy). Pain and light sensitivity can be quite severe, especially in conditions affecting the outermost layer (epithelium) of the cornea. Examples include traumatic abrasions, infectious ulcers, and erosions from dryness.
IMAGESSee a picture of eye diseases and conditions See Images
What types of healthcare specialists diagnose and treat corneal disease?
Vision problems are diagnosed and treated by eye doctors (optometrists and ophthalmologists). For more advanced corneal conditions, particularly those requiring surgery, an ophthalmologist (medical doctor/eye surgeon) or a corneal specialist (an ophthalmologist who has undergone additional fellowship training) would provide treatment.
Additional specialists such as oculoplastic surgeons (ophthalmologists who specialize in eyelid and orbital surgery), rheumatologists, infectious disease and allergy specialists, and others may be consulted when the cornea is secondarily affected by other medical conditions.
How do healthcare professionals diagnose corneal disease?
An eye doctor will review the person's medical history and perform a careful examination of the eyes and eyelids. The cornea is examined in detail using a slit lamp microscope.
Additional medical testing that can provide the information needed to make a diagnosis may include:
- Topography and keratometry (to study the shape of the cornea)
- Pachymetry (to measure the thickness of the cornea)
- Specialized microscopy (providing detailed pictures to assess the health of the endothelial cells, or to identify infectious agents)
- Assessment of the tear film
In some individuals, cultures, biopsies, or blood tests are also necessary.
What is the treatment for corneal disease?
Treatment is tailored to the individual disease and the individual patient. Treatments might include medications, laser treatment, or surgery, depending on the condition.
Infections are treated with medicated eyedrops (antibiotics, antivirals, and antiparasitics) and, in some cases, oral medication. Herpetic stromal keratitis is a recurring swelling that develops after a herpes eye infection and is managed with anti-inflammatory steroid eye drops.
An abrasion might require temporary patching or a bandage contact lens, depending on the cause and extent of the injury.
Keratoconus, in which the cornea can take on a distorted cone shape, is often managed with special contact lenses. Newer treatments, including corneal crosslinking (riboflavin and ultraviolet-A) and corneal implants, are also options. Advanced keratoconus diseases are treated with anterior lamellar keratoplasty or corneal transplant surgery.
Chronic swelling from Fuchs' dystrophy or other conditions that damage the cornea's endothelial cells is managed initially with salty eyedrops or ointments that help prevent the accumulation of fluid within the cornea. If the condition worsens, an endothelial lamellar keratoplasty (a type of partial-thickness transplant surgery) may be indicated.
Research is underway to develop an artificial cornea for transplantation.
Autoimmune disorders are best treated by addressing the underlying disease. Corneal involvement is often managed with anti-inflammatory eyedrops such as steroids; however, steroid-sparing immune-modulating medications are sometimes preferable, particularly when other parts of the body are also involved.
Eye problems caused by vitamin A deficiency, which can be seen in patients who have had certain types of bariatric (weight loss) surgery, can be corrected with supplements.
Allergic eye disease responds well to both topical and oral allergy medication.
A pterygium is a growth on the cornea's surface; this is most commonly seen after chronic sun exposure. They can be removed surgically if they become bothersome. Cancers of the surface of the eye are managed with surgery or in some cases, topical chemotherapy eyedrops or injections.
A dry eye is common and can result in painful erosions of the corneal surface. Aside from lubricating the eyes with artificial tears, addressing the underlying cause is important. In some individuals, dryness is due to a lack of tear production, and anti-inflammatory drops such as cyclosporine (Restasis) or steroids may help. In other cases, the dryness is due to the evaporation of the tears between blinks. This occurs when the eyelids' oil glands (Meibomian glands) are not functioning well. Normally, the oil from these glands coats the eye's surface and prevents tear evaporation. The oil glands' function can be improved with a combination of warm compresses, lid hygiene (for example, dilute baby shampoo lid scrubs), increased intake of omega-3 fatty acids, and in some patients, oral medication.
- CDC Warns of Potentially Fatal Bacterial Illness on U.S. Gulf Coast
- Helping Others as Volunteers Helps Kids 'Flourish': Study
- FDA Approves Pfizer's RSV Shot for Older Adults
- What to Do When Tough-to-Treat Lymphoma Strikes During Pregnancy
- Rate of Pregnant U.S. Women Who Have Diabetes Keeps Rising
- More Health News »
What are the potential complications of corneal disease?
Many corneal diseases are treatable and have a good prognosis. However, vision loss and chronic eye pain are potential complications of corneal disease so it is important to review treatment options carefully with an eye doctor.
Is it possible to prevent corneal disease?
Many corneal diseases are preventable by reducing risk factors. For example, maintaining optimal eye health (with good hygiene and regular vaccinations) is the best prevention against many infectious diseases. There are vaccines available to reduce the severity and frequency of shingles, which can result in an eye herpes infection called herpes zoster ophthalmicus.
Contact lens wear can make individuals especially susceptible to serious corneal infections, so people should clean contact lenses as directed. Glasses and sunglasses with 100% ultraviolet block can protect against growths that are associated with sun exposure, such as pterygium, and eye surface cancers. Safety glasses should be worn when warranted to prevent trauma. A diet rich in omega-3 fatty acids and sufficient vitamin A may help maintain a healthy tear film, thus minimizing dry eye symptoms.
Reviewing one's family's ocular health history helps look for hereditary conditions. Regular eye examinations are important for detecting eye diseases at their earliest stages.
Health Solutions From Our Sponsors
Randleman, J.B., S.S. Khandelwal, and F. Hafezi. "Corneal cross-linking." Surv Ophthalmol 60.6 Nov.-Dec. 2015: 509-523.
Reidy, James J. Basic and Clinical Course 2010-2011 Section 8: External Disease and Cornea. Revised edition. American Academy of Ophthalmology, 2010.
Top Corneal Disease Related Articles
Allergy (Allergies)An allergy refers to a misguided reaction by our immune system in response to bodily contact with certain foreign substances. When these allergens come in contact with the body, it causes the immune system to develop an allergic reaction in people who are allergic to it. It is estimated that 50 million North Americans are affected by allergic conditions. The parts of the body that are prone to react to allergies include the eyes, nose, lungs, skin, and stomach. Common allergic disorders include hay fever, asthma, allergic eyes, allergic eczema, hives, and allergic shock.
Astigmatism PictureAstigmatism is a common form of visual impairment in which an image is blurred due to an irregularity in the curvature of the front surface of the eye, the cornea. See a picture of Astigmatism and learn more about the health topic.
Dry EyesDry eyes are caused by an imbalance in the tear-flow system of the eye, but also can be caused by the drying out of the tear film. This can be due to dry air created by air conditioning, heat, or other environmental conditions. Treatment may involve self-care measures, medications, or rarely, surgery.
Common Eye ProblemsEye diseases can cause damage and blindness if not treated soon enough. Learn the warning signs and symptoms of common eye conditions such as glaucoma, cataracts, pink eye, macular degeneration and more.
Fatigue and Exhaustion
Fatigue can be described in various ways. Sometimes fatigue is described as feeling a lack of energy and motivation (both mental and physical). The causes of fatigue are generally related to a variety of conditions or diseases, for example, anemia, mono, medications, sleep problems, cancer, anxiety, heart disease, and drug abuse.Treatment of fatigue is generally directed toward the condition or disease that is causing the fatigue.
Genetic DiseasesThe definition of a genetic disease is a disorder or condition caused by abnormalities in a person's genome. Some types of genetic inheritance include single inheritance, including cystic fibrosis, sickle cell anemia, Marfan syndrome, and hemochromatosis. Other types of genetic diseases include multifactorial inheritance. Still other types of genetic diseases include chromosome abnormalities (for example, Turner syndrome, and Klinefelter syndrome), and mitochondrial inheritance (for example, epilepsy and dementia).
GlaucomaGlaucoma is a common eye condition in which the fluid pressure inside the eye rises because of slowed fluid drainage from the eye. If untreated, glaucoma may damage the optic nerve and other parts of the eye, causing the loss of vision or even blindness.
HeadacheHeadaches can be divided into two categories: primary headaches and secondary headaches. Migraine headaches, tension headaches, and cluster headaches are considered primary headaches. Secondary headaches are caused by disease. Headache symptoms vary with the headache type. Over-the-counter pain relievers provide short-term relief for most headaches.
Vaccination Schedule for Adults and AdolescentsImmunizations can prevent many diseases nowadays. It's important to follow the vaccination guidelines recommended on the CDC's vaccination schedule for adults and adolescents in order to stay informed about new vaccines and to learn how often and when the vaccines should be administered.
LASIK Eye SurgeryLASIK (laser in situ keratomileusis) eye surgery is a procedure in which a laser is used beneath the corneal flap to reshape the cornea. This process is used to treat refractive errors, improve vision, and eliminate or reduce the need for contact lenses or glasses. LASIK eye surgery comes in three main types: conventional LASIK, wavefront-optimized LASIK, and wavefront-guided LASIK.
Nausea and VomitingNausea and vomiting are symptoms of many conditions including motion sickness, pregnancy, emotional stress, gallbladder disease, and other illnesses. Learn about causes, treatment, and when to be concerned.
Omega-3 Fatty AcidsOmega-3 fatty acids are essential fats that help decrease one's cholesterol and triglyceride levels as well as reduce the risk of coronary artery disease. Omega-3s are found in salmon, sardines, walnuts, and canola oil. These fats may help reduce the risk of ventricular fibrillation and sudden cardiac death.