Anterior Lamellar Keratoplasty (ALK)

When scarring or corneal disease involves the front (anterior) part of the cornea, there are two surgical options to consider.

The first,  Penetrating Keratoplasty (PK), is the traditional full thickness transplant where all three main layers of the cornea--the epithelium, stroma and endothelium--are removed and replaced with donor tissue. This process involves the use of a cookie cutter like tool, called a trephine, to remove the existing cornea. The trephine is also used to cut the donor cornea so the tissues are the same size. The donor cornea is then positioned on the eye in place of the diseased cornea and sutured into place.

Visual recovery in patients can take between 6-24 months and many require the use of contact lenses to obtain useful vision. Patients in need of transplants in both eyes much wait an average of 12 months to receive treatment in their second eye until any issues with the first are are resolved. The results last for 10 to 20 tears, sometimes longer but often less.

Anterior LamALK-co.jpgellar Keratoplasty (ALK) is an alternative treatment that selectively replaces the front part of the cornea when it is scarred or distorted.  In ALK, the surgeon dissects the cornea into two thin pieces and removes the front, scarred part. A matching area of healthy tissue from a donor cornea is then used to replace the area that was removed. This procedure is less invasive than a penetrating keratoplasty. Your eye will be stronger after surgery and you will be able to resume normal activities sooner. Depending on the type of ALK, sutures may or may not be needed.

Best vision is oDeep-ALK-co.jpgbtained with a type of ALK known as Deep Anterior Lamellar Keratoplasty (DALK), in which the surgeon only leaves behind 5% or less of your original corneal thickness and replaces the rest with donor tissue.  DALK surgery can be done with a manual or hand dissection of donor tissue or by using air to detach the inner layer of your cornea with a technique called the “big bubble” developed by Dr. Anwar of Saudi Arabia which has since been adopted around the world. We have found that using a femtosecond laser to make the incisions can facilitate the DALK technique. DALK is our treatment of choice for keratoconus or corneal scars, as long as the inner cell layer of the cornea (the endothelium) is healthy.

DALK is the strongest transplant type partly because the surgery never enters the eye. Unlike a PK, a DALK transplant can last the lifetime of the patient. This is especially important for a young, active person.

Zigzag vs. Straight Incision:  What's right for you?
It's important to choose a skilled surgeon when considering a cornea transplant of any kind. In addition to deciding whether or not to remove the endothelium in a PK or leave it intact with an ALK or DALK, there is a new option to have either a straight or zigzag incision.

The straight incision is hand cut with a trephine as noted previously whereas a zigzag incision is cut with a femtosecond laser that precisely creates interlocking incisions.

Zigzag-co.jpgThe principal advantages of the interlocking zigzag incision over the straight incision are that the zigzag helps align the front surfaces of the donor and recipient corneas, much like a boat floating in a boat dock. This helps to reduce potential visual distortions. The zigzag is like tongue-in-groove construction--creating a stronger wound which results in more secure and faster healing allowing patients to get back to their normal lives sooner and with greater confidence.

Rejection with ALK & DALK

Epithelial and stromal cells (the two layers removed with ALK and DALK) can regenerate, while the  endothelial cells (back layer) cannot. With ALK and DALK, patients retain their own endothelium so the risk of a patient's immune system rejecting the tissue is dramatically reduced, which means patients can discontinue use of the corticosteroid eye drops used to prevent rejection sooner. These drops have side effects for some patients that can lead to glacuoma and cataracts, so shortening the time a patient uses these medications will reduce the chances for these adverse effects to occur. Since these drops slow wound healing, stopping sooner means faster healing time and earlier suture removal.