Issue 9.17
The clear protective layer of the front of the eye, the cornea, is responsible for focusing light entering the eye and producing a sharp image on the retina. Disease and damage of the cornea can distort light entering the eye, causing blurry vision, glare, and sensitivity to light. Corneal eye disease is the fourth most common cause of blindness, and affects more than 10 million people worldwide.
The cornea can lose transparency due to many different problems. Corneal infections and trauma may lead to scarring. Conditions such as keratoconus gradually transform the shape of the cornea from a symmetrically round shape to a cone shape. Other conditions, such as Fuchs corneal dystrophy may arise from a problem with only a single layer of the cornea, causing swelling and clouding of the cornea. Surgical intervention is often needed to improve vision in such cases.
A corneal transplant replaces the damaged, scarred or diseased tissue with healthy tissue from a donor. According to the Eye Bank Association of American, 79,304 transplants were performed in 2015. There are two main types of transplants that can be performed: a full thickness transplant, known as a penetrating keratoplasty (PKP), and a partial thickness transplant, called an endothelial keratoplasty (EK).
Traditional transplant surgery, penetrating keratoplasty, is used for severely distorted or scarred corneas. In this procedure the central full thickness of the cornea is removed and replaced with a clear, healthy donor. The donor is held in place with several sutures, which remain in place for a year or more after surgery. Visual recovery can take several months to a year, and oftentimes results in irregularity that requires a contact lens for the best vision.
Newer types of corneal transplants, such as endothelial keratoplasty, replace only the diseased portion of the cornea, leaving healthy tissue intact. There are two types: Descemets’ Stripping Automated Endothelial Keratoplasty (DSAEK) and Descemet’s Membrane Endothelial Keratosplaty (DMEK). In both procedures, a small incision is made and the innermost layer of the cornea is removed and replaced with a donor graft. Compared to full thickness transplants, partial thickness transplants preserve a more regular and uniform shape to the cornea, and allow significantly faster visual recovery.
DSAEK has been performed since 2003, and is the most common type of endothelial keratoplasty. In this procedure, a donor graft consisting of the inner 20-30% of the cornea in inserted into the patient’s eye. An air bubble is placed to hold the graft in position. No sutures are used to hold the graft in place. Visual recovery usually takes 1-3 months, with most patients achieving vision that is 20/30.
DMEK is a newer technique of endothelial keratoplasty. The donor graft used is much thinner, only about 5% the thickness of the cornea. Because the tissue is thinner, a smaller incision can be made. In addition, visual recovery can be faster than DSAEK, with vision approaching 20/25 or even 20/20.
As with all types of surgery, there is a risk of complications arising from a corneal transplant. These can include new corneal donor tissue being rejected by the body, infection, or other visual problems. It’s important that care be taken to ensure a successful recovery.
Jayson Edwards, MD is the only fellowship trained cornea specialist in St. George, Mesquite and Cedar City. He specializes in diseases affecting the cornea, including keratoconus, corneal dystrophies, infections and ocular surface reconstruction. He performs corneal transplants, DSAEK and DMEK surgery, LASIK, cataract surgery and other complicated surgeries involving the front of the eye. For more information call Zion Eye Institute at 435-656-2020 or visit www.zioneye.com