Cornea
Corneal Disorders
Corneal diseases can cause permanent damage to the eyes, sometimes severely impairing ision. Our ophthalmologists in North Carolina provide the latest corneal treatments, including PTK laser surgery and corneal transplant surgery. With the proper diagnosis and treatment, corneal damage can be corrected and vision significantly improved.
What Is the Cornea?
The cornea is the clear, dome-shaped outermost layer of the eye. It is comprised of highly organized cells and proteins that cover and protect the iris and the pupil. Unlike most other tissues, the cornea contains no blood vessels, instead deriving nourishment from fluids in the area behind it. The cornea’s transparent quality is what allows light to refract (bend) onto the eye’s natural lens, which in turn focuses that light onto the retina. From the retina, light is then transmitted to the brain via the optic nerve, producing images.
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The cornea is composed of five main layers, each with its own specialized function.
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Epithelium
The epithelium is the outermost layer of the cornea and accounts for almost 10 percent of its thickness. It functions primarily to prevent foreign particles from entering the eye, while its smooth surface facilitates the absorption of nutrients from fluids in the eye by redistributing them to the inner layers of the cornea. Highly sensitive, the epithelium contains thousands of nerve endings and may cause pain when rubbed or scratched.
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Bowman’s Layer
Bowman’s layer is a strong, transparent sheet of collagen that protects the stroma that lies just below it. Bowman’s layer is prone to scarring when it is damaged; when scars are centrally located, impaired vision may result.
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Stroma
The stroma is located in the middle of the cornea and accounts for about 90 percent of corneal thickness. It is primarily a water-based structure but also contains uniquely arranged collagen fibers that are essential to light refraction and visual clarity. During refractive surgery such as LASIK and PRK, our ophthalmologists reshape the stroma to correct nearsighted, farsighted, or astigmatic vision.
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Descemet’s Membrane
Descemet’s membrane is a highly elastic collagen structure, made by endothelial cells that lie beneath it, that protects the cornea against injury and infection. Upon injury, Descemet’s membrane regenerates quickly.
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Endothelium
The endothelium, the deepest layer of the cornea, is essential to ocular health. It acts as a pump, maintaining a balance of fluids flowing into and out of the stroma. If the endothelium is damaged, fluid can build up in the stroma, causing the cornea to become hazy or opaque. The swelling of the cornea (corneal edema) can ultimately result in blindness. Corneal transplants are necessary for individuals with severe damage of the endothelium.
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Corneal Diseases
There is a wide spectrum of corneal diseases, ranging from minor refractive errors such as nearsightedness to severe forms of corneal dystrophy that lead to pain and swelling of the eye as well as significant vision loss. Our ophthalmologists in North Carolina treat all forms of corneal disease. Dr. Sheel Patel is a cornea specialist, performing a wide variety of surgical procedures to treat corneal diseases. The most common corneal diseases are described below.
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Refractive Errors
A refractive error occurs when the curvature of the cornea is irregular—either too flat or overly curved—so that light is not refracted properly onto the retina. Instead, the retina receives an unfocused light image, which results in blurry or otherwise distorted vision. Patients with refractive errors such as nearsightedness, farsightedness, and astigmatism require prescription eyeglasses, contact lenses, or refractive surgery in order to achieve vision. The optometrists, ophthalmologists, and LASIK surgeons at Cape Fear Eye Associates can help you if your vision has been affected by any of these conditions. To learn more about refractive vision correction and other remedies, contact our LASIK centers in North Carolina.
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Keratitis
Keratitis is the inflammation of the cornea, which tends to make the eyes red, watery, overly sensitive to light, and subject to pain. Causes of keratitis include bacterial, viral, and fungal infections; overexposure to ultraviolet light; foreign particles such as dust or pollen; dry eyes; contact lens use; vitamin A deficiency; and trauma to the eye or the entry of a foreign object.
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If keratitis is caused by a viral or bacterial infection, our ophthalmologists may prescribe antivirals or antibiotics in eyedrop form. Artificial tears are also often recommended for keratitis caused by dry eye syndrome. And although most patients recover fully from keratitis, corneal damage causing impaired vision is a risk. If such damage has occurred, laser surgery (PTK) or a corneal transplant may be necessary to restore vision, depending on the severity of the case.
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Ocular Herpes (Herpes of the Eye)
Herpes simplex is the virus that causes cold sores on the face, usually near the mouth. It can also affect the eyes, causing a form of keratitis. Typically when this occurs, only one of the eyes is affected. Redness and excessive tearing can occur, and an opacity or scar sometimes appears on the cornea, usually causing considerable pain or light sensitivity. In most cases, our ophthalmologists treat superficial ocular herpes with antiviral eyedrops or gently remove damaged corneal cells with a dry cotton swab. In more severe cases, topical steroids may be recommended to reduce inflammation. If extensive corneal damage has occurred due to ocular herpes, a corneal transplant may be necessary to improve vision.
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Herpes Zoster (Shingles)
Herpes zoster, more commonly known as shingles, is caused by varicella-zoster virus, the same virus that causes chicken pox. Once exposure to the virus has occurred (usually in childhood), the virus remains dormant in the nerve fibers of the body and can become active during times of stress, illness, or decreased immune system function. Aging can also cause the virus to become active. If the nerve branch related to the eye is affected, blisters or sores may develop on the eyelid, possibly scratching, inflaming, and even scarring the cornea. Chronic herpes zoster can also cause secondary eye diseases such as cataracts and glaucoma. It is therefore important that you seek medical attention right away to have this condition treated.
Our ophthalmologists treat herpes zoster with one or more of the following therapies: systemic anti-herpetic medication, anti-viral eyedrops or ointment, lubricating eyedrops, and topical steroids.
J. Wayne Riggins, OD, MD Video - Shingles
Corneal Dystrophies
A corneal dystrophy is a potentially vision-impairing condition characterized by a buildup of cells or tissue in one of the five corneal layers. Typically inherited, a corneal dystrophy develops slowly over time, affecting both the right and left eye. Some corneal dystrophies can be effectively treated with eyedrops or ointments, while others may require corneal transplant surgery. Our ophthalmologists have extensive experience in the diagnosis and treatment of corneal dystrophies. While there are over 20 different known corneal dystrophies, the following are the most common types:
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Fuchs’ Dystrophy
A very slowly progressing disease, Fuchs’ dystrophy involves the deterioration of the endothelial cells in the inner layer of the cornea. Because damaged endothelial cells are less able to pump fluid out of the stroma, they often cause the central layer of the cornea to swell, thereby distorting vision. In advanced cases of Fuchs’ dystrophy, the epithelium absorbs fluid as well, causing blisters, pain, and severe visual impairment.
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Keratoconus
Keratoconus is characterized by thinning of the stroma, the middle layer of the cornea. As the stroma thins, it begins to bulge outward, eventually becoming cone-shaped. This distortion of the stroma causes refractive errors that interfere with a person’s eyesight. Swelling and scarring may occur as well, further impairing vision.
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Stromal Dystrophies (Lattice, Granular, Macular)
Lattice dystrophy is the abnormal accumulation of protein fibers on the middle and outer layers of the stroma. These deposits generally look like clear dots and branches that overlay one another, creating a lattice effect. As the disease progresses, the deposits become opaque and may begin to cover more of the stroma, causing the cornea to become cloudy. If deposits develop between the epithelium and the stroma, epithelial erosion can occur, causing significant pain and refractive errors. Other forms of stromal dystrophies which can cause vision loss include granular and macular dystrophies.
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Map-Dot-Fingerprint Dystrophy
Map-dot-fingerprint dystrophy involves the abnormal development of the membrane below the epithelium, which causes structural irregularities in the cornea. Under a microscope, the cornea appears to be covered by opaque dots and growths that resemble fingers and continents on a map. Most people with this type of corneal dystrophy do not suffer significant vision loss. However, in a small percentage of those affected, map-dot-fingerprint dystrophy results in epithelial erosions, which cause pain in the eyes and make them watery and sensitive to light. Blurry vision may also occur as a result of epithelial erosion or scarring.
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Treatment for Corneal Diseases
When corneal diseases damage the eye, there are a number of treatments available at Cape Fear Eye Associates to help restore vision. Our ophthalmologists perform phototherapeutic keratectomy (PTK) laser surgery to correct superficial corneal irregularities. We also offer corneal transplant surgery (keratoplasty) for patients with more severe corneal damage.
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PTK (Phototherapeutic Keratectomy)
Using an excimer laser, our ophthalmologists in North Carolina can treat many forms of superficial corneal damage caused by infections, dystrophies, and other vision problems. To remove superficial roughness or cloudiness of the cornea, the pulsed ultraviolet radiation of the excimer laser evaporates the outer layers of the cornea without damaging surrounding tissue. The result is a smoother corneal surface and improved vision. Compared to surgery with a blade, PTK with the excimer laser is incredibly accurate and involves minimal risk of scarring.
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Following the procedure, our ophthalmologists apply topical antibiotics and anti-inflammatory medication to reduce the risk of infection and promote healing. A patch is then placed over the eye to protect it from dust particles and bright light. Patients are able to leave immediately following surgery, but they will need someone to drive them home. There may be some minor discomfort in the days following surgery, in which case over-the-counter analgesics usually provide sufficient relief.
Sheel Patel, MD Video - Corneal Disorders
Corneal Transplant (Keratoplasty)
A corneal transplant is used to treat severe corneal damage caused by Fuchs’ dystrophy, corneal edema, keratoconus, herpes simplex, shingles, trauma, and various other corneal diseases. During keratoplasty, damaged corneal tissue is removed and replaced with healthy donor tissue in order to minimize the effects of eye disease.
A very precise form of surgery, a corneal transplant is performed under a surgical microscope. Using a special surgical instrument, ophthalmologists first remove the damaged area of the cornea. Next, precisely cut donor tissue is transplanted and stitched into place with ultrafine nylon sutures.
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Following surgery, your treated eye is covered with a soft eye patch as well as a hard eye shield. Patients will need to arrange for someone to drive them home, as vision is temporarily impaired after corneal transplant surgery.
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The procedure takes one to two hours, depending on each person’s needs. It is performed on an outpatient basis while the patient is under local or general anesthesia. For patients with more complex eye disorders, our ophthalmologists often combine corneal transplant surgery with cataract surgery and the placement of intraocular lens implants.
DSAEK (Descemet’s Stripping Automated Endothelial Keratoplasty)
DSAEK is the next-generation corneal transplant. Indicated for diseases of the corneal endothelium such as corneal edema and Fuchs’ Dystrophy, DSAEK preserves up to 95 percent of the cornea, depending on the nature of the patient’s disease. It is therefore considered a “cornea-sparing” procedure.
The DSAEK procedure entails the removal of damaged endothelial corneal tissue and replacement with donor tissue. After the eye is anesthetized, an incision is made in the eye, and a special instrument is used to remove a circular portion of the diseased inner layers of the patient’s cornea. The donor tissue is then cut, prepared, and then inserted into the eye. An air bubble is used fill the front of the eye and enables the new tissue to adhere to the surrounding cornea. Part of the air bubble is released either at the end of surgery or one hour later. The patient will return the following day so that one of our ophthalmologists can check the tissue’s position and make any corrections that are necessary.
Unlike a traditional corneal transplant, DSAEK requires no stitching and prevents significant astigmatism from developing postoperatively. It also provides for quicker visual recovery and healing, taking only a few months instead of a year. Following DSAEK, the cornea is more stable, structurally stronger, and more resistant to injury compared to after a full-thickness corneal transplant. DSAEK also reduces the risks associated with traditional corneal transplant, such as hemorrhaging and vision loss. DSAEK is not right for everyone. Only experienced ophthalmologists can determine whether DSAEK is the appropriate treatment for your specific corneal problem.
Contact Our Ophthalmologists for Treatment of Corneal Diseases
If you are experiencing pain, redness, blurred vision, or excessive tearing of the eyes, you may have a corneal disorder. Our ophthalmologists in North Carolina can provide you with an exam, an evaluation, and treatment for your condition. Contact Cape Fear Eye Associates today to schedule an appointment.
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