Cornea Conditions & Updates
Cornea Transplants
A corneal transplant involves replacing a cloudy cornea with a clear donor cornea. The cornea is the clear part in the front of the eye - the window of the eye. It allows light to pass through and come to focus on the retina. The cornea must remain clear to provide good vision. Corneal disease, degeneration and scarring from injury can all cause the cornea to become cloudy and result in decreased vision. If visual decrease is significant, a corneal transplant may be necessary.
THE DONOR CORNEA comes from individuals who have donated their eyes for the benefit of others. The donor is carefully screened for many infections and diseases including hepatitis, syphyilis and AIDS. An eye bank network is used to obtain a donor cornea and ensure the safe use of the tissue.
A PENETRATING CORNEAL TRANSPLANT "PK", or standard full thickness transplant, involves the surgical removal of the central two-thirds of the damaged cornea. It is then replaced with clear, healthy donor tissue. The new cornea is held in place by sutures. This is the most common type of corneal transplant. This type of transplant has the potential to provide the clearest vision after healing because there is no interface (layer) to look through. However, the healing time is longer and the use of a contact lens might be required for the clearest vision.
ANTERIOR LAMELLAR CORNEAL TRANSPLANT "ALK" is performed when scarring involves the front part of the cornea. Your cornea is dissected in half and the front of it is removed. The new donor cornea is then sewn in place. This procedure is less invasive and your eye will be stronger after surgery than it would be with a regular full thickness transplant. However, there can be some loss of clarity from the interface between the new and remaining layers of the cornea.
DSEK (DESCEMET’S STRIPPING WITH ENDOTHELIAL KERATOPLASTY) is a cornea-sparing transplant, performed through a small incision, to remove and replace the inner cell layer of the cornea when it stops working properly. With this technique, Dr. Price gently strips off the single diseased cell layer, leaving the rest of the patient’s cornea intact. He then thinly slices a donor cornea, folds the back portion in half and inserts it through a small incision into the eye. He uses an air bubble to unfold and position the donor tissue on the recipient cornea. Within a few minutes the donor tissue attaches to the recipient without the use of any sutures. The most important advantages of DSEK are:
- the eye remains much stronger and more resistant to accidental injury
- visual recovery is very rapid with 50% of patients seeing 20/40 or better within 1 month of surgery, and some seeing 20/25 within 1 week
- the surgery causes minimal change in astigmatism or glasses prescription, in contrast to a penetrating graft, where there can be large and unpredictable changes in astigmatism
Dr. Price has taught the DSEK technique to hundreds of doctors in the United States and Europe. He is one of the few doctors in the world to have performed more than 4000 corneal transplants. The doctors of the Price Vision Group are actively involved in physician education through their association with the Cornea Research Foundation of America. They have been principle investigators on many research projects dealing with the medical and surgical treatment of corneal disease and disorders. They also participate in lectures at local and national scientific meetings and are acknowledged to be among the leaders in the field of corneal surgery. A number of studies have shown a definite improvement in transplant survival when the surgery is performed in a center that specializes in corneal transplants. Dr. Price and his team of doctors in the clinic are part of one of the busiest and most successful corneal transplant centers in the world. Experience like theirs is unmatched in all but a handful of other centers. This experience will help you have a successful result from your surgery.
Replacing most, but not quite all of the corneal thickness in a technique called DALK may provide the best visual results."
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Fuchs' Dystrophy
First described in 1910, Fuchs' dystrophy is an inherited disorder of the deepest layer of the cornea (endothelium) with severity varying from asymptomatic disease apparent only on biomicroscopic examination to frank corneal decompensation and severe visual loss. The condition is dominant, and roughly half of an affected person's offspring will have the condition. However, the degree to which the condition is expressed is variable, and may be more or less severe in the offspring than in the parent. Symptoms are uncommon prior to the age of 50 years. Both eyes are affected, although asymmetry may be present. Women are more likely to develop the characteristic finding (cornea guttata, see below), and are five times as likely as males to develop corneal edema.
The initial findings in Fuchs' dystrophy are cornea guttata, which appear as dark spots on the corneal endothelium. The guttae may spread peripherally, and may become confluent, giving rise to a "beaten metal" appearance of the endothelium. As the condition progresses, the size and shape of the endothelial cells varies (pleomorphism and polymegathism), and the number of cells decreases. The normal function of these cells is to pump water out of the cornea, and as they decrease in number and cease to function normally, swelling of the cornea occurs. The swelling causes the cornea to lose its normal transparency, and blurred vision results. Severe swelling can cause blisters, or bullae, of the superficial layer of the cornea, leading to discomfort and pain.
Often, the first symptom is blurred vision worse in the morning, improving over the course of the day. This occurs because evaporation of fluid from the cornea is decreased while the eyes are closed during sleep, and accumulation of fluid in the cornea during the night results in corneal swelling (edema).
Treatment of mild or early cases includes use of hypertonic saline drops to draw fluid out of the cornea, use of a blow dryer across the eyes to increase tear evaporation, and reduction of intraocular pressure. These therapies have limited efficacy, and are not helpful in more advanced cases.
Corneal transplantation is necessary when the vision is diminished sufficiently to impair the quality of life, or if ruptured epithelial blisters result in pain. The success rate of corneal transplantation for Fuchs’ dystrophy is very high. Results from the Cornea Research Foundation of America transplant database have shown clear grafts in 98% of patients 5 years after surgery, which are among the best results reported in the medical literature. The database shows that with a standard penetrating keratoplasty, 50% of patients achieved vision of 20/40 or better within 3 months of surgery. With the newer cornea-sparing DSEK (Descemet’s stripping with endothelial keratoplasty) procedure, visual recovery is significantly faster and 50% of the patients achieved 20/40 or better vision within 1 month of surgery and some could even read the 20/25 line one week after surgery. Dr. Price no longer recommends penetrating grafts for Fuchs’ dystrophy, he only recommends DSEK.
Cataract is often detected in patients with Fuchs’ dystrophy. Dr. Price prefers to first have the cataract removed and then perform DSEK. Cataract surgery and DSEK can be performed on the same day.
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Keratoconus
: Keratoconus Study :
Keratoconus (KCN) is a disease characterized by thinning and protrusion of the cornea, resulting in an irregular, conical shape. Irregular astigmatism occurs as the condition progresses, and results in blurred vision which can be impossible to correct with spectacles. Usually the disease occurs in both eyes, and involves the central cornea with the apex of the cone just below the visual axis.
Approximately 100 to 200 of every 100,000 people are afflicted with keratoconus and it occurs in all races and usually affects both eyes. Sensitive techniques, such as corneal topography, often detect KCN in both eyes in cases thought to be only in one eye based on physical examination and refraction. The disease often starts in puberty and slowly progresses over decades and then stabilizes. In progressive cases, severe irregular astigmatism and scarring may require a corneal transplant in order to restore useful vision to the eye.
Heredity of the disease has not been clearly established. While there are families in which multiple persons are affected, factors such as allergic conditions and contact lens use make analysis difficult. As a general rule, chances of a blood relative developing clinical keratoconus are less than 10%.
NORMAL EYE |
KERATOCONUS |
Associated conditions include atopic disease (atopic or allergic dermatitis, allergic rhinitis, asthma), Down's syndrome (5-8 % of Down's patients), and connective tissue disorders (Ehlers-Danlos syndrome and osteogenesis imperfecta). Chronic eye rubbing is associated with KCN and may accelerate progression of the disease.
Findings in keratoconus include protrusion of the cornea, striae or wrinkles of the posterior cornea (Vogt's striae), superficial scarring of the anterior cornea, and staining of the corneal surface epithelium with iron (Fleischer ring). Corneal hydrops, or marked swelling of the cornea may occur when severe bulging of the cornea results in a tear in the deepest layer of the cornea (Descemet's membrane), allowing fluid from the inside of the eye to permeate the cornea. Severe haziness, often accompanied by blisterlike lesions of the superficial cornea, result in impairment of vision and discomfort.
Treatment of keratoconus can be divided into three tiers. For patients who can be corrected with spectacles, no other treatment is necessary, although behavior such as eye rubbing should be modified. Control of systemic allergic disease with antihistamines may help achieve this goal by decreasing itching of the eye and eyelids.
When irregular astigmatism makes clear vision with spectacles impossible, rigid gas permeable (RGP) contact lenses are the next stage of therapy. The rigid lens masks the underlying irregular cornea and functions as the new refractive surface of the eye, with the tear film filling in the space between the back of the contact lens and the front of the eye. However, the irregular shape of the cornea makes fitting these lenses difficult, and the experience and expertise of the contact lens fitter is very important in determining the success of this intervention. New surgical techniques such as deep anterior lamellar keratoplasty and intrastromal ring segments (Intacs TM) are also surgical options.
If the condition progresses to the point where a contact lens cannot be fit, surgery may be indicated. Small plastic ring segments placed in the cornea can produce a more regular corneal surface in about 2 out of 3 KCN patients. A new treatment to strengthen the cornea is also being evaluated to halt the progression of keratoconus. As a last resort, a cornea transplant may be considered to restore a more normal shape to the cornea. Data from the CRFA database of corneal transplant shows that transplants performed for keratoconus are in the highest category for successful outcome. Newer transplant techniques, such as deep anterior lamellar keratoplasty (DALK) are used by surgeons at Price Vision Group to help minimize the risk of graft rejection.
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