Corneal Diseases and Disorders
There are a wide variety of diseases and disorders that affect the cornea. Some are serious and may lead to a corneal transplant, while others are simply irritating and can be dealt with through drops, medication, or other interventions.
Dry Eyes
Dry eyes are one of the most common ocular problems, affecting 59 million Americans. Patients with this problem have a variety of symptoms including itchy, red or watery eyes. Dry eyes can also lead to blurry vision or light sensitivity. Other common complaints include a burning sensation or a feeling that there is something in the eye.
Dry eyes result from problems with any of the three layers of tears which normally cover and protect the eye. The eye's surface is covered first by a mucus layer which keeps the eye moist and allows other tears to stick to the eye. The second layer of tears are the watery tears with which people are most familiar. The final layer of tears is an oily layer which is designed to prevent the other tears from evaporating.
The eye's ability to produce adequate layers of tear film can be impaired for several reasons, but the most common is the natural aging process. As people age, their tear production naturally declines. In fact, dry eyes affect approximately 75% of people over age 65. Tear production can also be inhibited by injuries to the eye, infections, and some diseases. Eye surgery can also result in a temporary decrease in tear production as can allergies or some medications. Contact lenses are also a significant contributor to dry eyes.
Fortunately, dry eyes can usually be managed effectively. People with dry eyes are advised to blink frequently to spread the tear film across the eye's surface and to rest their eyes frequently. In most cases, supplementing the eye's natural lubrication with artificial tears is the most effective way of minimizing the problem. Artificial tears are widely available without a prescription. Artificial tears should be used regularly, according to the severity of the dry eye problem. People with occasional problems can use tears as needed, but those with more severe dry eyes should use the tears frequently, before their eyes become sore and irritated. As symptoms diminish, artificial tears can be used less often.
If artificial tears do not solve the problem, other treatment options are available. Punctal plugs, which are also called punctum plugs, are used to block the "puncta", small openings in the eye through which tears drain. In a quick office procedure, soft silicone plugs are gently inserted into the punctal opening by an eye doctor. Punctal plugs usually provide rapid relief, but if they are not helpful they can be removed easily. In some cases, punctal plugs may be needed permanently, but they can be removed when the eye's natural lubrication improves.
Corneal Dystrophy
Corneal dystrophy is a term used to describe several conditions in which one or more parts of the cornea have lost their normal clarity. There are over 20 different types of corneal dystrophies, the most common of which are Keratoconus and Fuchs' Dystrophy. These diseases have the following common features:
- They are usually inherited.
- They affect both eyes.
- They are not caused from external factors such as injury or diet.
- Most do not affect other parts of the body.
- Most are not related to other diseases elsewhere in the body.
- They can occur in otherwise healthy individuals.
- Most progress gradually.
Keratoconus
Usually diagnosed in people in their early teens to mid-twenties, keratoconus is the most common corneal dystrophy in the United States. Keratoconus develops when the central cornea thins and gradually bulges outward in a rounded cone shape. This curvature can produce moderate to severe visual distortion. People with keratoconus tend to become very myopic (nearsighted) and to have irregular and often rapidly fluctuating astigmatism. Keratoconus almost always affects both eyes, although it will usually develop in one eye several months to years before it appears in the second eye. Keratoconus is progressive, meaning it takes several years to develop. It can start at any time and can also stop progressing at any stage. Doctors cannot usually predict how rapidly the condition will progress.
In the early stages of the disease, vision can usually be corrected with glasses or contacts. As keratoconus progresses, customized contact lenses may be required to reduce visual distortion. Sometimes the cornea scars or cannot tolerate a contact lens. In these cases, a corneal transplant is usually necessary.
Fuchs' Dystrophy
Fuchs' dystrophy is a slowly progressing disease affecting the corneal endothelium (the innermost cells of the cornea). This dystrophy occurs when the endothelial cells gradually deteriorate and become unable to maintain a fluid barrier between the cornea and the rest of the eye. In this situation, the cornea retains too much fluid. The cornea then swells, altering its curvature and leading to blurry vision. This corneal swelling can also lead to the development of haze within the corneal stroma (the central layer of the cornea) or to the formation of blisters on the corneal surface.
Treatment for Fuchs' dystrophy usually involves drops or ointments intended to decrease the swelling. When medications cease to be effective, a corneal transplant is indicated.
Herpes Simplex Virus
Ocular herpes, or herpes of the eye, is the most common infectious cause of corneal blindness in the United States. The infection is persistent and once people are infected, they have a 50/50 chance of a repeat infection. The infection can recur weeks or even years after the initial infection.
The early symptoms of a herpes simplex infection include mild pain, excess tearing, light sensitivity and redness. Normally, the infection clears on its own, but if it does not, it can produce painful sores on the eyelid or the surface of the eye, causing inflammation of the cornea. Early treatment with antiviral drugs can help to stop the herpes virus. Unfortunately, the infection can spread deeper into the cornea and develop into a more severe, sight-threatening infection. In these cases, a corneal transplant may be necessary, but the patient must be symptom free for six to twelve months before the surgery can be performed.
Corneal Transplants
A corneal transplant, also known as a corneal graft or a penetrating keratoplasty, is often the final attempt to preserve sight when a cornea has been badly damaged or scarred. First developed in 1905, corneal transplants became a reliable form of corneal surgery in the early 1950s. Since that time, over half a million corneal transplants have been performed in the US. In 1999 alone, over 40,000 corneal transplants were performed, accounting for over two-thirds of all transplant surgeries in that year. With a success rate of over 90%, corneal transplants have the best outcomes of any transplant surgery.
There are many reasons for the success of corneal transplants, but one of the major factors is the nature of the cornea itself. Because the cornea does not contain blood vessels, the transplant patient's antibodies and white blood cells do not circulate in the donated cornea. This minimizes the recipient's immune response and thereby reduces the risk of rejection.
The success of corneal transplants also depends upon the generosity of donors. If corneal transplants and other organ transplant programs are to continue to save people's vision or their lives, it is vitally important that everyone sign the organ donor form on their driver's license.
The Corneal Transplant Procedure
When you arrive at Casey Eye Institute on the day of your corneal transplant, enter through the front doors and go to the surgery reception desk on the 6th floor. Our receptionist will be expecting you.
Prior to your surgery, you will be taken to the *preparation area** where you will meet the nurse and anesthetist. You will be given a hospital gown to change into and the nurse will set up an intravenous (I.V.). Then, the anesthetist will dispense the anesthetic to be used during your surgery. Initially, you will not be "put to sleep." Instead, you will be sedated. You will be drowsy and relaxed but you will not be able to feel anything. You will then be wheeled into the operating room where you will be given a general anesthetic. The general anesthetic will last for about five minutes, during which you will be given a retrobulbar anesthetic. This is a special kind of anesthesia that only affects your eye. You will be unable to move the eye or see out of it, and, of course, you will not feel any pain. Once the retrobulbar anesthetic has been administered, you will be woken from the general anesthetic. You will still be sedated, so you will feel relaxed during the surgery.
The first step in the surgery is the removal of your corneal tissue. A special device known as a trephine is used to remove a circular "button" of tissue from your cornea. The surgeon then shapes the donor corneal tissue and carefully places it on your cornea. (Before your surgery, the donor tissue was carefully inspected by your surgeon.) The new corneal tissue is held in place with very fine sutures, which remain in place for up to year after surgery. Then, the surgeon rehydrates the eye with a special solution and closely checks the cornea to ensure there are no leaks. Then your eye is patched and the surgery is over.
If necessary, additional surgical procedures can be performed at the same time as the transplant. The most common combination is the removal of a cataract and the insertion of an intraocular lens. But, surgeons can also perform other procedures such as a trabeculectomy to relieve glaucoma. In these situations, the corneal transplant is usually done after the other procedure has been completed.
After Surgery
After surgery, you will be taken to the recovery area where you will be monitored by the nurse. When the nurse is satisfied that you are ready to go home, you will be able to leave. You will be given pain pills, but you will probably not need to use them; most corneal transplant patients do not experience pain after surgery.
Once you go home, it is important that you follow your post-operative instructions carefully. These include:
- Wear your eye shield at night for as long as your surgeon recommends. You can expect to use it for two to three months.
- Use all eye drops as directed. If you have problems with any eye drops, contact your surgeon. Do not discontinue use without checking with the surgeon first.
- Do not drive until you have your surgeon's approval.
- Do not rub your eye.
- Avoid heavy lifting.
- Stay out of swimming pools and hot tubs.
- Keep your eyes closed in the shower.
- Avoid dust, smoke (including cigarette smoke) and other eye irritants.
Follow-up Appointments
The day after surgery, you will need to return to the Casey Eye Institute. Your patch will be removed and your vision will be checked. You can expect to have blurry vision because of the dilation drops and ointments in your eye. Your eye will probably be red, teary and sensitive to light. The stitches on your cornea will also be visible.
Although corneal transplants do not cause pain, some patients do notice discomfort in the first week after surgery. If this happens, you can expect the discomfort to peak in the first week. The most common complaints are watery eyes or a scratchy feeling in the eye.
Your surgeon will want to see you frequently after your surgery, so you can expect to come back to the Casey Eye Institute three days after surgery and again at two weeks, four weeks, three months and then as directed.
Because corneal healing varies greatly from one person to another, it is important not to have preconceptions about your own recovery. Depending on how well your cornea heals, your stitches will be removed anytime between three months and one year after surgery. Your vision will return gradually, often taking six to twelve months to stabilize.
Risks and Benefits of Corneal Transplants
Although corneal transplants are highly successful, there are some risks associated with the procedure. One of the most significant risks is that of rejection, although this is not common and can often be halted with prompt treatment. Warning symptoms include persistent discomfort, excessive light sensitivity, persistent redness or changes in vision. Any of these problems should be reported to your surgeon immediately.
Other potential complications of the surgery include infection (endophthalmitis), which can be treated with antibiotics; retinal detachment, which can usually be surgically repaired; and glaucoma, which can be treated with eye drops.
It should be noted that even a successful corneal transplant does not guarantee perfect vision. Glasses or contact lenses may be needed after surgery to maximize vision.
There are also statistical risks associated with anesthesia; these will be explained to you by the anesthesiologist.
Potential risks can be intimidating, but these are balanced by the considerable benefits of the surgery. A cloudy or scarred cornea significantly impairs vision. When it is replaced with a clear cornea, the world of light and color is restored. Many patients are delighted to resume activities which had been precluded by their poor vision.
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