The cornea is the clear layer in front of the iris and pupil that keeps dirt, germs, and particles out of the more delicate areas of the eye. While the cornea is sensitive to touch and appears fragile, it is actually about as stiff as a fingernail. The cornea helps the eye with light refraction and therefore impacts the eye’s ability to focus. The cornea is composed of three main layers: the epithelium is the outermost layer that prevents foreign objects from entering the eye, the stroma is the thickest layer in the center, and the endothelium is the innermost layer that expels excess water to keep the eye appropriately hydrated. Damage to any of these layers can cause corneal disease, which covers a variety of disorders that afflict the cornea.
Bullous Keratopathy. This is a swelling of the eye that leads to blisters on the cornea. These blisters can cause sensitivity to light, blurring of vision, and, if ruptured, pain and the sense of a foreign object in the eye.
Cogan Syndrome. This is a rare autoimmune disease. When Cogan syndrome affects the cornea, it can cause eye pain, impaired vision, sensitivity to light, and redness of the eye. These symptoms are also shared with diseases such as Lyme disease, syphilis, and the Epstein-Barr virus and a person with Cogan syndrome will likely have to be tested for all of these to rule them out.
Corneal Ulcer. This ulcer can be caused by infections of bacteria, fungi, viruses, or parasites, although it can also be caused by injuries such as scratches, abrasions, or penetration to the cornea. Injury is most commonly caused by wearing contacts while sleeping or not properly disinfecting them. Corneal ulcers may appear as white or grey spots in the eye and they can cause pain, redness, tear overproduction, sensitivity to light, and the sensation that something is in the eye.
Herpes Simplex Keratitis. This is the same virus that causes cold sores. While the herpes simplex virus can be dormant, it never goes away after initial infection. The virus can reactivate in the eye in the form of a primary herpes simplex eye infection, which is similar to pink eye. The virus can reactivate multiple times after primary eye infection, each time causing more damage to the cornea and potentially leading to scarring or numbness of the cornea.
Herpes Zoster Ophthalmicus. This is caused by the same virus that causes chickenpox and shingles. Once infected, this virus can become dormant and can activate later, causing aches, swelling, redness, and light sensitivity in the eye, with infection and inflammation of the cornea. This virus can lead to glaucoma and can also damage the uveitis behind the cornea.
Interstitial Keratitis. This eye disorder, while rare, is most likely to occur in children or teenagers as a result of congenital syphilis, although other causes include Cogan syndrome, Lyme disease, Epstein-Barr virus, acquired syphilis, herpes simplex, varicella-zoster virus, and tuberculosis. This disorder causes inflammation in the middle layer of the cornea.
Keratoconjunctivitis Sicca. More commonly known as Dry Eye Syndrome or DES, this eye condition limits the tear production in the eye and the quality of tear production so that the eye either doesn’t produce enough tears or the tears do not have enough lubricating oils to keep the eyes moisturized. Dry eye symptoms are most common in dry climates, such as Alberta.
Keratoconus. This eye disorder typically affects both eyes and causes the cornea to slowly change to become cone-shaped. This causes frequent changes to the vision that requires routine prescription updates.
Keratomalacia. This eye disorder is typically caused by a vitamin A deficiency and it leads to the drying of the cornea. This increases the risk of corneal ulcers and infections, as well as a clouding of the cornea.
Peripheral Ulcerative Keratitis. Most common in people with connective tissue disorders, this eye condition causes the development of an ulcer in the margin of the cornea as well as inflammation of the cornea.
Phlyctenular Keratoconjunctivitis. This autoimmune reaction to bacteria causes the development of small, yellow-grey bumps on the eye. The bumps typically last up to 2 weeks and often heal without scarring.
Superficial Punctate Keratitis. This eye disorder is caused by the death of small groups of cells on the surface layer of the cornea, but other cells will grow to replace them and most people with this disorder will recover.
If you are suffering from eye pain, eye irritation, sensitivity to light, the feeling of a foreign object in your eye, clouding of the eye, or any other eye discomfort or vision impairment, visit a Calgary optometrist. When you book an eye exam at My Optometrist in Calgary or Three Hills, our highly skilled optometrists will examine your eye for any conditions, including all of these corneal diseases. To book an eye exam at one of our three locations at Health First in SE Calgary, Sunridge in NE Calgary, or Three Hills, AB, you can call us or fill out the online contact form.
Q: What are the most common types of corneal disease?
A: The most common types of corneal conditions are the result of injury, particularly from abrasions or allergies. The most common corneal diseases are keratitis, keratoconjunctivitis sicca, and herpes zoster ophthalmicus.
Q: Can corneal scars fade?
A: While some forms of corneal scarring can fade, it will depend on the type of corneal disease that caused it and the severity of the condition. If you are suffering from corneal disease, discuss the potential outcomes with your optometrist.
Q: How does an optometrist test for corneal disease?
A: Your optometrist will use a slit lamp exam. During this exam, the optometrist will have you rest your head and chin on the device and will look into your eye using a low-powered microscope and a slit lamp. If your optometrist needs a better view of your cornea, they may use eye drops that contain a yellow dye called fluorescein. This dye will make abnormalities on the cornea more visible and the dye will naturally wash away with your tears. Dilating eye drops may be used if the optometrist needs to see more of the cornea.
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