DSLEK Corneal Transplantation

The basics:
The cornea is the clear, living tissue on the very front part of the eye. Light passes through the clear cornea on its path toward the retina in the back part of the eye. Sometimes, the cornea is refered to as the "window" to the eye.

Occasionally, either through disease or injury, the corneal tissue is damaged to a point where light can no longer effectively pass through it, resulting in reduced vision. Where indicated by an ophthalmologist, a corneal transplant procedure may be performed which replaces the damaged cornea with a clear donor cornea. This is an extremely delicate microsurgical procedure.

What is DSLEK?

DSLEK is a corneal 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 DSLEK procedure utilizes a much smaller surgical incision and requires no corneal sutures. This usually results in more rapid visual rehabilitation for the DSLEK patient and also reduces the risk of sight threatening complications that may occur with the PKP procedure such as intraoperative expulsive hemorrhage or post operative traumatic wound rupture.

Who is a candidate?
DSLEK is indicated for those patients who have corneal pathology located on the posterior aspect of their cornea known as the endothelial layer. The endothelial layer of the cornea is a monolayer of cells attached to a basement membrane called Descemet’s membrane. A healthy endothelial layer consists of small, hexagonally shaped cells with a density of 2500 to 3000 cells/mm2.

Figure 1a - Healthy monolayer of endothelial cells attached to Descemet’s membrane. Red line in the leftmost figure represents Descemet’s membrane and endothelium. The middle diagram represents an enlargement of a cross section that from top to bottom includes the epithelial layer (a), stromal layer (b), Descemet’s membrane with attached monolayer of endothelial cells (c) and anterior chamber (d). The rightmost diagram illustrates normal size and shape of healthy endothelial cells.

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.

When the corneal endothelium is stressed, the endothelial cells become larger and more sparse. As endothelial cell density falls between 500 to 1000 cells/mm, the pump mechanism can no longer maintain a clear cornea. In the case of Fuchs' dystrophy the endothelial cells also start secreting material that makes Descemet’s layer thicker and more opaque. Vision eventually deteriorates to a point where these patients feel like they are looking through wax paper. Such patients are good candidates for the DSLEK procedure.

Figure 1b - Unhealthy monolayer of endothelial cells attached to Descemet’s membrane. The middle diagram illustrates a cross section of an over hydrated swollen cornea. The top layer of epithelial cells have formed bullae or blisters (a) and the stroma is thickened with vacuolated spaces (b) both of which are the result of over hydration. A sparse covering of stressed endothelial cells lies over a thickened Descemet’s membrane (c). The rightmost figure depicts large, low density, irregularly shaped endothelial cells.