There are approximately 45,000 Cornea Transplant surgeries performed each year in the United States. This is actually a small number when compared with approximately 3,500,000 cataract procedures each year in this country. Of all transplant surgery done today, including heart, lung and kidney, corneal transplants are by far the most common and successful. Richard A Erdey, MD and Daryl D Kaswinkel, MD are Corneal Specialists; they have been performing Cornea Transplant Surgery since 1988 and 1996 respectively.
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The Human Eye is like a telescope in that it contains two lenses to focus light onto the retina. The first “lens” is the cornea which is a transparent, dome-shaped structure covering the front of the eye. It is a powerful refracting surface, accounting for 2/3 of the eye’s focusing ability. Because there are no blood vessels in the cornea, it is normally clear and transparent. Like the crystal on a watch, it provides a clear window to look through. To the observer, it glistens due to the constant bathing of tears equally spread onto its surface with each blink of the lids.
The cornea is tough, difficult to penetrate and is extremely sensitive – there are more nerve endings in the cornea than anywhere else in the body. For this reason, a corneal abrasion is generally very painful but fortunately, heals rapidly. The adult cornea is only about 1/2 millimeter thick and is comprised of 5 layers: Epithelium, Bowman’s membrane, Stroma, Descemet’s membrane and the Endothelium. Throughout life the cornea must remain transparent, smooth and of regular curvature to properly transmit and focus light as it enters the eye. Infections, trauma, or dystrophic conditions can involve any layer of the cornea and may result in scarring, thinning or curvature distortion that, if severe, can cause loss of transparency, optical distortion and blindness.
Cross-section of the cornea. The normal cornea is about 0.55 millimeters (mm) thick in its center and consists of five microscopic layers as labeled above. The thickness may increase to 0.68 mm or greater if swelling occurs because of endothelial cell loss.
We are born with a complement of cornea endothelial cells (3000 to 3500 cells/ mm²) that line Descemet’s membrane. These cells are responsible for “pumping” fluid out of the cornea, maintaining cornea transparency. As we mature, the concentration of these specialized cells may decrease by 1/3 but this quantity is still sufficient to maintain corneal clarity throughout life. Unfortunately, corneal endothelial cells are one of the few cells in the human body that are not capable of regeneration and if damaged or lost are not replaced.
If the cornea endothelial cell concentration falls below a certain critical threshold, as can occur in Fuchs’ Corneal Dystrophy, after cataract or cornea transplantation surgery or after eye trauma, the cornea swells and loses transparency leading to blurry vision or eventually, blindness.
Fuchs’ corneal dystrophy is a progressive condition that gradually affects both eyes. It is slightly more prevalent in women than in men. The condition rarely affects vision until people reach their 50s and 60s although an eye doctor can sometimes detect the early signs of Fuchs’ dystrophy at age 30 to 40 years. The pathology in Fuchs’ corneal dystrophy is demonstrated by increasing concentrations of optically degrading tiny dimples which form within descemet’s membrane in between the endothelial cells. The endothelial cells are gradually lost over the years.
At first, a person with Fuchs’ corneal dystrophy may notice subtle deterioration in night vision. As the process progresses, they may awaken with blurry vision that gradually clears later in the morning or later. The reason for this is during sleep the closed eyelids prevent evaporation; once the patient awakens, the open eyelids allow corneal surface evaporation to occur, allowing the cornea to thin and vision to improve. As the disease progresses further, corneal swelling will remain constant and vision remains poor throughout the day.
Eventually, the epithelium also swells with fluid and may form tiny blisters, causing eye irritation, foreign body sensation and severe visual impairment. If these blisters burst they can cause severe pain. These symptoms are also seen with other causes of corneal endothelial failure due to cataract surgery, corneal transplant rejection/late failure, or trauma.
To treat the disease, your doctor may initially try to reduce corneal swelling with hypertonic salt drops or ointment which temporarily extracts the fluid from the cornea. If the condition becomes painful, bandage soft contact lenses may be used. In early stages of this condition, a hair dryer held at arm’s length and directed parallel to face can be used to dry and thin the cornea. This technique may briefly improve symptoms and can be repeated if necessary.
Once the disease interferes with daily activities because visual performance is consistently reduced and/or persistent pain occurs, your doctor may recommend corneal transplantation to restore sight and eliminate discomfort.
There are other conditions of the cornea where the endothelial cells are healthy but the cornea may be scarred, abnormally thinned, warped and distorted. As a result, the light passing through the cornea is not focused as it should. This occurs in advanced Keratoconus, LASIK-induced ectasia (thinning), Radial Keratotomy (RK) induced irregularity, traumatic injury, or various corneal dystrophies.
Corneal Transplantation may be necessary if your cornea is damaged due to injury or disease. Since there is no artificial substitute for corneal tissue, a human donor cornea is transplanted to restore sight. The Central Ohio Lions Eye Bank typically provides the corneal tissue for our patients.
A successful Corneal Transplant requires special, ongoing care and attention on the part of both patient and physician. However, no other surgery has so much to offer when the cornea is deeply scarred or afflicted with disease. View: testimonials
“Don’t take your organs to heaven…heaven knows we need them here! “
Corneal Transplant Surgery would not be possible without the hundreds of thousands of generous donors and their families who have donated corneal tissue so that others may see. If you would like more information on becoming a donor, please contact the Central Ohio Lions Eye Bank at (614) 293-8114 or (800) 301-4960
Drs. Erdey and Kaswinkel may recommend one of the following surgical variations of corneal transplantation at the time of your consultation:
Penetrating Keratoplasty (PK) is a traditional full-thickness corneal transplant. This may be required in cases where the cornea is scarred, swollen or excessively thin (Keratoconus).
Return of best vision after standard full thickness corneal transplantation may take up to a year or more after the operation. It is dependent on how long it takes for the grafted cornea to begin functioning as a lens; it must become transparent and it must have a regular surface curve. These important characteristics permit light to properly bend (refract) as it passes through the cornea, bending further as it passes through the crystalline lens and comes to focus on the retina.
The newly grafted cornea, if successful, only takes a few weeks to become thin and transparent but far more time is usually required until light is properly refracted through it.
The healthy cornea is transparent because it does not contain the fine blood vessels (capillaries) present in other tissues of the body. However, this lack of blood supply has a downside when cornea graft wound-healing is required. The cornea takes years to heal as compared to a superficial wound in the skin of your arm, which heals in only about a week! For this reason cornea graft sutures must be left in place for a year or more while the cornea graft-host interface heals. The tension generated by the sutures within the cornea often cause distortion of the curvature of the graft, causing the refraction of the eye to shift unpredictably. If the cornea surface is regular, and the prescription of the other eye is not too different, it is sometimes possible to prescribe glasses during this early rehabilitation period but the prescription lenses may need to be periodically changed as the cornea heals.
Some patients may need to wait until the sutures can be removed (1 to 1.5yrs) before the final surface topography is apparent and then glasses are prescribed. However, if after suture removal, significant cornea graft distortion or warpage (irregular astigmatism) remains, spectacles will not help. Instead, hard contact lenses may be suggested, but fitting can be challenging and is not always successful.
Other individuals require laser vision correction to reduce inadequate graft curvature or imbalances between the prescriptions of both eyes to maximize optical visual rehabilitation.
Of course, a good visual outcome is also dependent on general eye health and requires the absence of other visually limiting conditions such as cataract, glaucoma, or macular degeneration.
Deep Anterior Lamellar Keratoplasty (DALK) is indicated to correct conditions which result in corneal thinning, distortion or scarring such as advanced Keratoconus, LASIK or Radial Keratotomy induced corneal thinning, corneal dystrophy, infection or trauma .
DALK is an elegant partial thickness graft that unlike full-thickness corneal transplatation (PK), preserves the TWO inner most layers of the cornea: Descemet’s membrane and the endothelium, while removing and replacing only the diseased, weakened or scarred anterior layers with donor tissue. If the endothelial layer is normal, then it is worth preserving!
DALK: Cross section of cornea showing partial thickness cornea graft. Note: Descemet’s membrane and endothelial cell layer is retained and NOT replaced.
Retention of this important layer not only may make a DALK graft last a lifetime and avoid rejection, but also makes the creation of larger diameter grafts possible. Since 2007, Dr. Erdey has refined techniques which permit the creation of larger diameter DALK grafts which tend to have less astigmatism, optical aberration and are associated with more rapid optical rehabilitation than smaller diameter grafts.
Read: Large-diameter DALK technique minimizes post-operative astigmatism - Richard A. Erdey, M.D.
Although DALK represents over 50% of the cornea grafts performed by Dr. Erdey and his team, very few cornea specialists offer this extremely delicate, time intensive and poorly reimbursed procedure despite it’s many benefits. In 2016, only 1232 DALK’s were performed in the USA. About 20,000 eyes had full-thickness traditional corneal transplants when the vast majority may have been suitable DALK candidates. Dr Erdey frequently speaks and teaches at local and national conferences to his colleagues in an effort to reduce the barriers to surgeon acceptance. He passionately believes broader surgeon acceptance and conversion to DALK will eventually occur.
|Cornea after DALK: donor graft applied to retained recipient descemet’s membrane. Cornea transparency is restored. Sutures generally removed after 6 mos.|
The most suitable candidates for this procedure generally include those with healthy cornea endothelium, no descemet’s membrane scarring and who have:
» Keratoconus, or LASIK-induced corneal ectasia (thinning) who are gas permeable hard contact lens intolerant and are poor candidates for INTACS
» cornea scarring restricted to the bowman’s membrane or stroma
» cornea surface warpage (irregular astigmatism) who are intolerant of hard contact lenses
» complications from Radial Keratotomy (RK)
» infectious keratitis unresponsive to medication
» Closed eye surgery
» No chance of potentially blinding endothelial rejection because the recipients own descemet’s membrane and endothelial cell layer is retained
» Can potentially repeat DALK or perform PK if the results of the original procedure are not satisfactory
» Better control of post-operative astigmatism particularly when large diameter grafts used.
» Conversion to full thickness PK may be required if perforation of descemet’s membrane - only 0.018 mm thick, about the thickness of cellophane, but not nearly as strong!
» Irregular astigmatism less common than PK but still possible
» Technically challenging
» Significantly longer operative time
» Offered by few cornea surgeons
Mastel Intraoperative Keratometer allows cornea graft running suture adjustment - reduces astigmatism and allows for rapid visual rehabilitation
See Dr. Erdey’s case studies below:
Descemet’s Stripping Endothelial Keratoplasty (DSEK) is a cornea-sparing transplant procedure, brought to Central Ohio in 2006 by Dr Erdey, indicated for patients without corneal scarring and with disease limited to the inner corneal layer (endothelium) such as Fuchs’ Endothelial Dystrophy or Pseudophakic Bullous Keratopathy.
|DSEK: Cross Section of Cornea showing partial thickness donor adherent to undersurface of a patient’s cornea|
Only the inner cornea layer is transplanted, leaving the patient’s cornea mostly intact. A small scleral incision is made and few sutures are required. The cornea heals very quickly and is less susceptible to injury or rupture as compared to standard PK. Visual recovery is much faster since the cornea’s original curvature is essentially unchanged resulting in little refractive shift. In contrast, after standard PK, patients often experience large changes in the amount of nearsightedness, farsightedness, and astigmatism. We no longer recommend traditional PK for suitable candidates with Fuchs’ Endothelial Dystrophy or Pseudophakic Bullous Keratopathy.
In 2010, Dr Erdey became the first in Ohio to routinely perform newer variations of DSEK called Descemet’s Memebrane Endothelial Keraoplasty (DMEK) and Descemet’s Membrane Automated Endothelial Keraotplasty (DMAEK). These variations require specially prepared cornea tissue from highly trained eye bank technicians. In 2011, with Dr. Erdey’s encouragement, Central Ohio Lions Eye Bank became only the second eye bank in the U.S. to offer this preparation! Drs. Erdey and Kaswinkel continue to refine, and currently prefer DMEK or DMAEK over DSEK in most cases, because of the higher probability of superior visual results. Also, In a recent study, the incidence of cornea rejection two years after DMEK surgery was 15x less compared to DSEK and 20x less compared to PK.
|Case 1: Cornea after DSEK: donor disc applied to inner cornea surface adds thickness due to retained donor stroma (note step-up - opaque wedge). Cornea transparency is restored.|
|Case 2: Cornea after DMEK: Cornea transparency and anatomy is restored to natural condition without adding additional thickness as in DSEK.|
As in any kind of surgery, many different complications can occur. One unique to corneal transplantation is rejection of the donated tissue. Cornea transplants are rejected five to 30 percent of the time and can occur any time after cornea transplantation. The rejected cornea clouds and vision deteriorates. The warning signs of cornea graft rejection are RSVP:
» Redness – graft rejection may be associated with a red eye
» Sensitivity – to light, any increase from your baseline
» Vision – decrease in vision, especially if foggy or cloudy
» Pain – discomfort, irritation or foreign body sensation
If YOU ARE EXPERIENCING ANY ONE OF THESE WARNING SIGNS, YOU MUST IMMEDIATELY CONTACT YOUR OPHTHALMOLOGIST AND SCHEDULE AN APPOINTMENT TO BE SEEN WITHIN 24 HOURS, EVEN IF MANY YEARS HAVE PASSED SINCE THE ORIGINAL CORNEA TRANSPLANT SURGERY!
Most rejections, if detected and treated promptly, can be reversed with minimal injury.
All cornea transplant patients are required to print, read and keep this document for future reference.
Never discard this important document! Be informed! If the transplanted cornea fails, the graft may be replaced with a new donor, usually with good results, but the overall rejection rates for repeated transplants are higher than for the first transplant.
Other possible complications listed below can usually be treated and include:
» retina swelling or detachment
» irregular astigmatism
After uncomplicated Corneal Transplantation, vision may continue to improve up to a year or more after surgery. If the surgery is successful, other existing eye conditions, such as macular degeneration, glaucoma, or diabetic retinopathy, may limit vision after surgery. Even with such problems, a corneal transplant may still be worthwhile.
Various Stem Cell Research projects may hold the promise of finding ways to stimulate corneal endothelial cell regeneration. This is the “holy grail” that could eventually eliminate cornea transplantation in cases of endothelial cell loss. Other research is dedicated to developing better artificial corneas or eventually regenerating entire living corneas for transplantation.
icanseeclearly.com – Cornea Transplantation PK, DALK, DSEK, DMEK, DMAEK Columbus, Ohio