CORNEAL GRAFTS

Femtosecond Assisted Corneal Transplant Surgery

Because the Femtosecond laser is able to cut corneal tissue at precise depths and in a variety of patterns, it has brought significant improvements to the outcomes of corneal transplantation eye surgery since its introduction.  Penetrating keratoplasty (PK), one of the more established techniques, has benefited greatly from the technology. The technically challenging conventional method of PK using a trephine blade often results in poor wound healing and severe astigmatism with post-op visual acuity less than optimal. With the Femtosecond laser, however, surgeons can create incision patterns that provide a broader surface area, resulting in a faster recovery of best corrected visual acuity and less induced astigmatism when compared to the conventional blade trephination incision.  In a recent study Femtosecond-assisted PK induced 1.5 D less astigmatism than the conventional technique, on average.  This lower degree of post-operative astigmatism is also easier to correct post-operatively with either Lasik or toric IOL’s if desired.

For patients who have the potential for good results, (who have no other ocular pathology) 65% will obtain functional vision in the operated eye with glasses by the third post-op month. This is a big advantage over conventional corneal transplant patients who need a minimum of 6 months to a year before they have any useful vision in the operated eye.

Probably the biggest reason for these improved results with the laser incision compared to traditional trephine incision PK is that the laser incision allows for more complex incisions, like top hat, zig-zag, mushroom and Christmas tree incisions.  All of these cuts are designed to provide a larger area of contact at the interface of donor / recipient tissue and to increase the wound’s stability.  The goal is to reduce the number of sutures needed to hold the graft in place and minimize the amount of astigmatism induced by the sutures.  The result is much faster visual recovery.

Femtocecond laser technology also enables surgeons to divide donated corneal tissue into anterior and posterior lamellar segments for use in partial thickness and Descemet-stripping endothelial keratoplasty (DSAEK).

Anterior Lamellar Keratoplasty (ALK) is a partial thickness grapht utilizing Femtosecond laser technology to selectively remove the diseased anterior layers of the cornea and preserves the two healthy innermost layers, the endothelium and Descemet’s membrane. As the inner layers are retained the body does not recognize the donor tissue, hence there is less risk of rejection.  This technique is typically used for the treatment of Keratoconus.

DSAEK Procedure (Descemet's Stripping Automated Endothelial Keratoplasty)

What is DSAEK?

DSAEK is a new corneal graft transplant technique where the unhealthy, diseased, posterior portion of a patient's cornea is removed and replaced with healthy donor tissue obtained from the eye bank. Unlike conventional corneal transplant surgery known as penetrating keratoplasty (PKP), the DSAEK procedure utilises a much smaller surgical incision and requires fewer corneal sutures. This usually results in more rapid visual rehabilitation for the DSAEK patient and also better post-operative visual acuity.

Who is a candidate?

DSAEK is indicated for those patients who have corneal pathology located on the posterior aspect of their cornea known as the endothelial layer. When endothelial cells are healthy, they function as a "pump-leak system" to provide nourishment for the cornea. In other words, these cells allow nourishing fluid from inside the eye (aqueous humor) to leak into the cornea. After the corneal cells have been nourished, the cells pump the fluid out of the cornea. If the endothelial pump is compromised for any reason the cornea will over hydrate and become cloudy. This most commonly occurs in patients who have sustained trauma to the endothelial layer during complicated cataract surgery or patients who have an inherited disease of the corneal endothelium known as Fuchs' Endothelial Dystrophy. Such patients are good candidates for the DSAEK procedure. It is also indicated for patients with endothelial rejection and bullous keratopathy.

DSAEK Corneal Transplantation Procedure

The first part of the DSAEK corneal transplant procedure involves removing unhealthy endothelial cells and attached Descemet’s membrane – the elastic layer found in the inner cornea. Once this has been done, the unhealthy tissue is replaced with healthy cells from a donor cornea. The entire procedure takes between 20 to 30 minutes to perform.

The patient is sedated approximately 30 minutes before the procedure, which can be performed under local or topical anaesthetic. The DSAEK procedure is performed under a special operating microscope as it is a microsurgical technique.

During the corneal graft, a femtoseond laser is used to cut both the donor and recipient cornea, as it is a very accurate and predictable way to cut corneas. In addition resultant astigmatism is much less and improved refractive outcomes are expected.

Once the procedure is complete, the small incision is closed with two or three sutures, which is less than with invasive keratoplasty procedures. The patient can then return home and return the next day for a follow up consultation on their corneal transplant.

Post-op visual recovery varies depending on the severity of the corneal cloudiness prior to surgery, but is much faster than with Penetrating Keratoplasty (PKP) procedures. Most patients notice improvement in their vision during the first two weeks after surgery with continued improvement during the next four to six weeks. This recovery represents a dramatic improvement over the time required following conventional corneal transplant surgery (PKP), which usually takes six to twelve months.