The cornea is the front clear “window” of the eye and is responsible for approximately two thirds of the eye’s focusing power. Healthy function of the cornea is required to maintain the unique clarity of this layer, and therefore all vision depends upon it. The cornea also forms the front wall of the eye and is therefore important for protecting the internal structures of the eye. If the cornea becomes hazy or cloudy, or if its shape or surface becomes very irregular, vision can be impaired. Such abnormalities may be caused by trauma, degenerative changes, or corneal diseases known as dystrophies. When vision impairment due to corneal disease affects daily function, total or partial replacement of the tissue by a corneal transplantation can often restore the optical clarity of the cornea.
Penetrating Keratoplasty (PK)
If the entire thickness of the cornea is damaged, a full thickness transplant is required. An entire circle of cornea is taken out and replaced by a donor cornea. It is sutured into place with multiple stitches that are thinner than human hair. Obtaining the best final vision will take approximately 6-12 months. Sutures will be removed individually after 3-4 months. Glasses or contacts will be prescribed after the cornea has healed.
Descemet’s Stripping Endothelial Keratoplasty (DSEK)
A great improvement in corneal transplantation has been the ability to avoid full thickness transplants in certain conditions. If only a small layer of the cornea is transplanted, the original natural shape, optical quality, and strength of a patient’s original cornea is more easily maintained. One of the most common causes of corneal clouding is dystrophy or disease of the lining (or endothelial cell layer) of the cornea only. These cells are responsible for pumping fluid out of the cornea. Because the unique clarity of corneal tissue requires an exact level of hydration, this function is vital. In patients with the condition known as Fuchs’ Dystrophy, for example, endothelial cells are increasingly lost over time, and this results in swelling of the cornea and loss of vision. (This is similar to the reversible cloudy wrinkling of fingertip skin that occurs after prolonged periods in the bath or swimming pool.)
DSEK offers a tremendous advantage over full thickness grafting for patients with endothelial disease. Rather than transplanting the entire thickness of cornea, the damaged endothelial cells are removed and replaced with a very thin healthy lining layer from a donor cornea. The new tissue is held in place with air in the eye on the day of surgery so that no sutures are required. It is important for patients to lie flat in a face up position on the day of surgery to allow the air to secure the new cornea in place while the new endothelial cells begin pumping fluid. Vision is recovered much more quickly compared to a full thickness transplant, and most people enjoy their best vision after 3 months.