Drs. Shivitz, Groos, Chang and Ewald are fellowship-trained cornea specialists whose additional training makes them uniquely qualified to perform corneal transplantation. Of all transplant surgery done today; including hearts, lungs and kidneys; corneal transplants are by far the most common and successful. The experience of our surgeons gives patients the feeling of confidence that they are good candidates for corneal transplantation, will undergo a highly skilled and appropriate procedure and will receive careful attention and instructions after surgery by our highly trained and attentive surgeons and staff.
What Conditions May Require a Corneal Transplant?
- Corneal failure after other eye surgery, such as cataract surgery.
- Keratoconus, a steep curving and thinning of the cornea.
- Hereditary corneal failure, such as Fuchs' dystrophy.
- Scarring after infections, most frequently herpes simplex.
- Failure following a first corneal transplant.
- Corneal scarring following traumatic injury.
What Types of Corneal Transplants Are There?
The first corneal transplants performed were penetrating keratoplasties (PK's) but were not widely performed until the 1970’s. A PK replaces a full-thickness, central piece of the diseased cornea with a similar sized piece from a donor cornea. Over the years various partial thickness corneal transplants, or lamellar keratoplasties (LK's), have been developed to speed recovery and reduce complications. The development of Descemets' stripping automated endothelial keratoplasty (DSAEK) and deep anterior lamellar keratoplasty (DALK) in particular has led to the decline of PK’s to the point that they have become a minority of the over 50,000 corneal transplants performed yearly in the US. Surgeons at Cornea and Cataract Consultants of Nashville have been at the forefront of introducing these procedures to Middle Tennessee and have the busiest practice performing these procedures from southern Kentucky to northern Alabama.
Of course, 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. For more information on corneal transplants, contact: The American Academy of Ophthalmology at www.aao.org. For more information on becoming a donor contact Tennessee Donor Services: http://tds.dcids.org.
Penetrating keratoplasty (PK) is the grandfather of all corneal transplants. First performed in 1905, the penetrating corneal transplant did not become a common procedure until the 1970's, when advancements in microscopes, suture material and eye banking solved many of the issues that had led to poor results and transplant survival. The last two decades have seen a decline in the percentage of this procedure as partial thickness procedures like DSAEK and DALK have been perfected to replace only the diseased layers of the cornea, reducing both recovery time and complication rates.
Which corneal diseases require a PK?
Though the penetrating corneal transplant or keratoplasty (PK) has become less widely used by corneal surgeons, a PK remains the only choice when faced with a cornea that has been destroyed by disease. These eyes have a cornea that has scarring of the collagen stroma and irreversible damage to the endothelial pumping cells. No layer is healthy enough to leave behind to allow for a partial or lamellar transplant. Patients with trauma and severe infections or eyes that have undergone multiple surgeries are often in this group. Although a PK is the most extensive corneal transplant it presents a high reward scenario, often resulting in dramatic and exciting recovery of vision.
The eyelid is gently opened. Looking through a surgical microscope, the ophthalmologist measures the eye for the size of the corneal transplant. The damaged cornea is removed, and a clear donor is sewn into place with sutures finer than a human hair. The patient’s eye is bandaged until the next morning, when the surgeon and staff remove the patch to examine the new cornea.
A successful corneal transplant requires care and attention on the part of both patient and physician. Eye drops are used to prevent infection and rejection of the corneal transplant, tapering slowly over the next year. Vision may continue to improve up to a year after surgery. Patients often need to wear glasses or contact lenses to achieve best vision. No other surgery has so much to offer when the cornea is so deeply scarred or swollen. The vast majority of people who undergo corneal transplants are happy with their improved vision.
Deep anterior lamellar keratoplasty (DALK) is a newer technique used to spare the patient’s endothelial cells if they are healthy while replacing the diseased collagen layer or stroma. The advantages of a DALK over a penetrating corneal transplant are a lower rate of rejection, more rapid recovery, and stronger eye once healed. The surgeons at Cornea and Cataract Consultants of Nashville are experienced in the indications and highly skilled in the execution of the DALK procedure.
Indications for a DALK
Replacing the scarred stroma of a diseased cornea is one of the more common indications for a DALK lamellar corneal transplant. Also, replacing the stretched and warped stromal layer of a keratoconus cornea with a healthy donor stomal layer creates a much more normally shaped cornea to focus images.
The DALK Procedure
The procedure begins in a similar fashion to a penetrating keratoplasty (PK) corneal transplant, but the surgeon sets the precisely cutting instrument – the Moria trephine – to a depth that will not cut through the entire thickness of the cornea. The donor cornea is cut to match but all layers are kept intact in case of the need to convert to a penetrating graft. Air is used to separate the layers of the cornea with a “big bubble” pushing the thinnest inner layers toward the inside of the eye. Careful dissection with scissors is needed to avoid puncturing the thin layer and necessitating conversion to a full-thickness procedure. Once the diseased stroma is safely removed from the recipient cornea, the thin back layers of the donor cornea are stripped away. The surgeon sews the donor to the recipient carefully and skillfully using suture finer than a human hair. A patch and protective shield are then placed over the eye to be worn until the following day.
After removing the patch the following day, the surgeon and staff at Cornea and Cataract Consultants of Nashville will assess vision and health of the graft. Antibiotic and anti-inflammatory drops are used by the patient to prevent infection and reduce inflammation and risk of rejection. The graft will be slowly molded into shape by removing sutures to release tension on the graft, targeting a more spherical basketball shape to allow for improved vision. The steroid anti-rejection drops can be tapered more rapidly with a DALK graft because of the lower risk of rejection. Spectacles or contact lenses may be worn after the graft reaches a stable point to correct vision, which may occur anywhere from 3 to 12 months after surgery. The majority of patients who have a DALK are very pleased with the improvement in vision the procedure creates.
Descemet's stripping automated endothelial keratoplasty (DSAEK) is a corneal transplant that replaces only the inner two layers of the cornea: the endothelium and Descemet’s membrane. Developed in the Netherlands and enhanced by surgeons in the US, this procedure was first performed in Middle Tennessee in 2005 by surgeons from Cornea and Cataract Consultants of Nashville.
What corneal diseases are good candidates for DSAEK?
Corneas that swell because of damage to the endothelial pump cells become cloudy as a result. An inherited condition called Fuchs’ corneal endothelial dystrophy is the most common reason to perform a DSAEK, followed by corneal graft failure and surgical trauma. The best results occur when the other layers of the cornea are normal or minimally damaged.
After cutting the donor corneal tissue to fit the patient’s eye, the surgeon carefully creates wounds similar to those in cataract surgery. The central portion of the thin inner layers of the patient’s cornea is gently removed. A thin disk of donor material containing new endothelial pump cells is placed carefully inside the eye and positioned against the patient’s cornea using an air bubble. One, two or sometimes no sutures are required to close the wound. The patient is positioned on their back in the recovery area for an hour to allow complete adhesion of the corneal graft to the host cornea. Before sending the patient home the surgeon partially replaces the air bubble with fluid to prevent glaucoma.
The patient has positioning restrictions for one to two days to allow the partial corneal graft to adhere. Drops are used to prevent infection and rejection. Vision recovery can be as soon as a week, with the best vision typically taking between 6-12 weeks to achieve. Improvement in vision can be seen in some patients for up to a year or more. The small incision makes the eye much stronger than with a penetrating corneal transplant, leading to more rapid recovery of stable vision. The risk of rejection is also lower with the partial DSAEK corneal graft than with a full thickness corneal transplant (PK).