Cornea & External Disease Conditions & Procedures
The cornea is the clear front window of the eye. It covers the iris (the colored portion of the eye) and the round pupil. The cornea is composed of five layers. The outermost layer is called the epithelium.
Injuries to the epithelium, such as scratches, cuts, or scrapes, are known as corneal abrasions. Usually, these injuries are caused by fingernail scratches, makeup brushes, paper cuts, or rubbing of the eyes. Sometimes conditions like dry eye can cause abrasions. Symptoms associated with corneal abrasions include tearing, redness, pain, soreness, and blurred vision.
Treatment options for corneal abrasions include patching the injured eye, dilating pupils to relieve pain, wearing special contact lenses that promote healing, taking antibiotics to prevent infection, and using lubricating eyedrops.
Minor abrasions usually heal within a day or two, while larger abrasions may take as long as one week.
Corneal erosion is caused by a loose attachment of the epithelium to the underlying tissue. This often happens at the site of an earlier abrasion. Some patients have an underlying condition called anerior basement membrane dystrophy that predisposes them to having recurrent corneal erosions.
Symptoms of corneal erosion are similar to those of abrasions: pain, soreness, redness, and blurred vision.
Treatment is the same as for corneal abrasion and may also include saline solution eyedrops or ointments. However, if the erosion keeps recurring, further treatment may be necessary. These treatments may include procedures to remove the damaged epithelium, removal of corneal cells using a laser, or performing an anterior stromal puncture, which involves making tiny holes on the surface of the cornea to promote stronger attachments between the top layer of corneal cells and the deeper layer of the cornea beneath.
Corneal ulcers can form due to trauma to the cornea, eyelid disease, severe dry eye, bacteria fungus, herpes simplex viral infections, and other causes.
There are two very common types of corneal ulcers. Bacterial ulcers tend to be painful, and if left untreated, can cause severe damage — even corneal perforation.
Improper care and handling of contact lenses can lead to infection and are often the cause of a corneal ulcer.
The symptoms of corneal ulcer may include:
- blurred vision
- sensitivity to light
Treatment for corneal ulcers depends on the cause. It usually includes frequent topical antibiotics, antifungal, or antiviral eyedrops. In some cases, hospitalization may be necessary in order to administer eyedrops every 15 to 30 minutes around the clock, for intravenous antibiotics, and for other treatments. In rare cases when the cornea is severely damaged, a corneal transplant may be necessary to save the eye.
Keratoconus is a condition in which the dome-shaped cornea (the clear front window of the eye) becomes thin and develops a cone-like bulge. As the condition progresses, the shape of the cornea is altered, distorting vision. Usually, keratoconus affects both eyes, although symptoms and progression in each eye may differ considerably.
Early symptoms include blurring of vision, increased sensitivity to light and glare, and mild eye irritation. The rate of progression varies. Keratoconus usually begins in the teenage years. It may progress slowly for 10 to 20 years and then stop progressing. As it progresses, the most common symptoms are blurring, increasing nearsightedness and astigmatism, inability to wear eyeglasses, and frequent contact lens prescription changes.
The cause of keratoconus is not known. Since an estimated 10% of people with keratoconus have a family member with the condition, genetics may play a role.
Keratoconus is usually corrected with eyeglasses. However, as the condition progresses, rigid contact lenses may be needed in order to improve vision. If vision is greatly affected, a corneal transplant may be necessary. While this procedure will relieve the blurred vision, it will not cure keratoconus. Nonetheless, corneal transplants offer the best prognosis for clear vision.
Two new techniques have recently been evaluated to treat early to moderate keratoconus. The first technique involves placing crescent-shaped acrylic inserts in the midperiphery of the cornea. This has been shown to be effective in some patients. the second technique involves the use of ultraviolet light and riboflavin to increase the stiffness of the cornea by causing greater cross linking of collagen that gives the cornea most of its thickness. This procedure is still experimental (and largely unavailable) in the United States, but results from European studies appear promising.
If the cornea is severely damaged or diseased, a corneal transplant may be required to restore your vision.
One type of corneal transplant, called a penetrating keratoplasty (PKP), replaces the central corneal tissue with donor tissue. The procedure usually takes about an hour under regional or general anesthesia, and the patient goes home the same day following surgery. After corneal transplant surgery, a plastic shield or eyeglasses is used to protect the eye, eyedrops are used to prevent infection and rejection of the donor tissue. An ophthalmologist (Eye M.D.) must monitor progress closely after surgery to ensure the best possible visual outcome and to control minor discomfort associated with the surgery and healing process. Vision usually returns gradually over the next 18 months. It is important to inform the ophthalmologist of pain, irritation, or redness of the eye following PKP, as this could be the earliest sign of infection or rejection, and early treatment of these conditions is critical to the viability of the graft.
Another corneal transplant procedure is called a lamellar keratoplasty. This is an advanced technique that replaces a specific layer of the cornea using donor tissue. In DSEK (Descemets Stripping Endothelial Keratoplasty) the deep layers of the cornea are replaced in order to reverse cornea edema. recovery is generally much faster than in penetrating keratoplasty, and the amount of astigmatism induced by the procedure is usually much less than in full-thickness keratoplasty.
Pterygium and Pinguecula
A pterygium is a mass of fleshy tissue that grows over the cornea (the clear front window of the eye). It may remain small or may grow large enough to interfere with vision. A pterygium most commonly occurs on the inner corner of the eye, but it can appear on the outer corner as well.
The exact cause of pterygium is not well understood. They occur more often in people who spend a lot of time outdoors, especially in humid, sunny climates. Long-term exposure to sunlight, especially to ultraviolet (UV) rays, and chronic eye irritation from dry, dusty conditions seem to play an important role. Dry eye also may contribute to pterygium.
When a pterygium becomes red and irritated, eyedrops or ointments can be used to help reduce the inflammation. If the pterygium grows rapidly or extends far enough to threaten sight, it can be removed surgically.
Despite proper surgical removal, a pterygium may return, particularly in young people. A number of surgical techniques are used by the surgeons at OASA to reduce the recurrence rate to as little as %5. Protecting the eyes from excessive ultraviolet light with proper sunglasses, avoiding dry, dusty conditions, and using artificial tears can reduce the rate of growth.
A pinguecula is a yellowish patch or bump on the white of the eye, most often on the side closest to the nose. It is not a tumor but is an alteration of normal tissue resulting in a deposit of protein and fat. Unlike a pterygium, a pinguecula does not actually grow onto the cornea. A pinguecula can also be a response to chronic eye irritation or sunlight.
No treatment is necessary unless the pinguecula becomes inflamed, since the pinguecula does not grow onto the cornea or threaten sight. On rare occasions, a pinguecula can be surgically removed if it is particularly annoying.
Fuchs' Dystrophy is a progressive disease that affects the cornea, the clear dome that covers the iris (the colored part of the eye) and helps focus light as it enters the eye.
In this condition, cells in the cornea's inner layer, called the endothelium, are reduced in number. This causes the overlying stromal cells to swell or thicken. The loss of endothelial cells can also allow abnormal dewdrop-shaped growths called guttata to form.
These cell changes may cause the cornea to become cloudy and swollen. Because Fuchs' Dystrophy is a progressive disease, the changes to the cornea can interfere with vision over time. Fuchs' Dystrophy usually occurs in people after age 40. Studies show that it is an inherited condition.
Symptoms of Fuchs' Dystrophy include hazy or cloudy vision that progresses slowly. In the early stages, as the cornea swells, vision in the morning may be hazy, but it clears up during the day. Once the disease has progressed to a more advanced stage, vision no longer clears, but remains blurred all the time.
It can take up to 20 years or longer for Fuchs' Dystrophy to progress from its earliest stage to a stage that is visually significant. To diagnose and monitor this condition, an ophthalmologist (Eye M.D.) checks for adequate endothelial cell number and function, measures the thickness of the cornea, and may obtainan endothelial cell count.
In its early stage, Fuchs' Dystrophy is treated with hypertonicsaline eyedrops to pull excess fluid from the cornea or by using a hairdryer to help dry the surface of the cornea. As Fuchs' Dystrophy advances, a therapeutic bandage contact lens may be used to lessen discomfort.
If vision loss begins to interfere with lifestyle in the latter stages of the disease, a corneal transplant technique known as penetrating keratoplasty or DSEK may be performed. These procedures have an excellent success rate.
Fungal keratitis is a serious infection of the cornea — the clear, round dome covering the eye's iris and pupil. Symptoms of fungal keratitis include:
- sudden blurry vision
- unusual redness of the eye
- pain in the eye
- excessive tearing or discharge from your eye
- increased light sensitivity
Risk factors for fungal keratitis include trauma (usually associated with plant material getting into the eye), chronic or ongoing disease of the surface of the eye, a compromised immune system, and, less-commonly, contact lens use. Keratitis is not transmitted from person to person.
Fungal keratitis is treated with topical, and sometimesoral antifungal medications. Patients who do not respond to medical treatment may require eye surgery, possibly including a corneal transplant.
Safe handling, storage, and cleaning of contact lenses are key measures for reducing the risk of infection. You should always use the following safe practices with your lenses:
- Wash your hands with soap and water and dry them before handling lenses.
- Wear and replace your lenses according to the schedule prescribed by your ophthalmologist (Eye M.D.).
- Follow instructions from your ophthalmologist and your lens solution manufacturer for cleaning and storing your lenses.
- Make sure you always use fresh lens solution and replenish the solution daily.
- Keep your contact lens case clean and replace it every three to six months.
- Remove your lenses and consult an ophthalmologist immediately if your eyes become red or irritated or if your vision changes.
No matter which cleaning or disinfecting solution you use, consider performing a rub and rinse lens cleaning method rather than a no-rub method. This can minimize the number of germs on your lenses, reducing your chances of infection.
Herpes keratitis is a viral infection of the eye caused by the herpes simplex virus, best known for causing cold sores. Herpes keratitis usually affects only one eye and most often occurs on the cornea, the normally clear dome that covers the front part of the eye.
The symptoms of herpes keratitis may include:
- blurred vision
- sensitivity to light
If the infection is superficial, involving only the cornea's top layer, called the epithelium, it will usually heal without scarring. However, if it involves the deeper layers of the cornea, it may lead to scarring of the cornea, loss of vision, and sometimes even blindness. Left untreated, herpes keratitis can severely damage the eye.
Herpes keratitis is usually treated with antiviral medications, in bothe the eyedrop and the pill form. Depending on the progression of the infection, your ophthalmologist (Eye M.D.) may later treat your condition with steroid eyedrops to reduce inflammation. Rarely, when the cornea is severely damaged, a corneal transplant may be necessary to restore vision.