Corneal Transplants
What is the Cornea?
The cornea is the transparent front “windshield” of the eye. It is responsible for two-thirds of the focusing power of the eye. If the cornea is damaged or irregular from injury or disease it can cause significant loss of vision.
5 Layers of the cornea
1. Epithelium: This outer layer of the cornea is 5 to 7 cells thick and measures about 50 microns - making it about 10 percent of the thickness of the entire cornea. Epithelial cells are constantly being produced from the peripheral “stem cells”. This is the layer that becomes redundant in conditions such as Map Dot Fingerprint and Salzmann’s Degeneration.
2. Bowman’s Layer: This is a very thin (8 to 14 microns) and dense fibrous sheet of connective tissue that forms the transition between the corneal epithelium and the underlying stroma.
3. Stroma: This middle layer of the cornea is approximately 500 microns thick, or about 90 percent of the thickness of the overall cornea. It is composed of strands of connective tissue called collagen fibrils. These fibrils are uniform in size and are arranged parallel to the cornea. The regular arrangement and uniform spacing of these lamellae is what enables the cornea to be perfectly clear. This is cornea that is thinned by the LASIK laser.
4. Descemet’s membrane: This very thin layer separates the stroma from the underlying endothelial layer of the cornea. Descemet’s (pronounced “DESS-eh-mays”) membrane gradually thickens throughout life - it’s about 5 microns thick in children and 15 microns thick in older adults.
5. Endothelium: This is the innermost layer of the cornea. The back of the endothelium is bathed in the clear aqueous humor that fills the space between the cornea and iris. The endothelium is only a single layer of cells thick and measures about 5 microns. Most of the endothelium cells are hexagonal (6 sided), but some may have five or seven sides. They function as microscopic pumps to keep the cornea hydrated and clear. Fuch’s Dystrophy causes loss of these cells resulting in the cornea becoming swollen.
Corneal transplantation is one of the most successful transplant surgeries in the world.
Corneal Transplants
If the cornea becomes damaged and vision is limited, a corneal transplant may be done to help restore some sight.
Corneal transplantation is one of the most successful transplant surgeries performed in the world. More than 40,000 corneal transplants are performed in the U.S. every year, and the procedure has a higher success rate than any other tissue transplant.
It can be required for any of the following reasons or conditions:
Keratoconus
Fuchs’ Dystrophy
Bullous Keratopathy
Corneal scarring from injury or chemical burns
Corneal ulcers
Types of Corneal Transplant Surgeries
There are three main types of corneal transplant surgeries: Endothelial Keratoplasty (EK), Penetrating Keratoplasty (PK) and Deep Anterior Lamellar Keratoplasty (DALK). Your doctor will decide which procedure is best suited for correcting your specific corneal condition. After a corneal transplant, it can take up to six months or longer to achieve your best vision.
Endothelial Keratoplasty
Endothelial Keratoplasty (EK) works by replacing just the inner layer of the cornea, leaving the remainder of your cornea intact. The transplanted tissue is initially held in place by an air or gas bubble inside the eye, which dissolves within the first week. The transplant tissue will attach in 90% of cases but may need to be reattached or replaced in some situations. Vision usually returns between two to four weeks, but best corrected vision may take three months or longer.
Deep Anterior Lamellar Keratoplasty
Deep Anterior Lamellar Keratoplasty (DALK) involves replacing the top four layers of the cornea leaving the innermost layer intact. Leaving the innermost layer intact can reduce the risk of transplant rejection over time. The transplanted tissue is held in place with sutures which are removed as the cornea heals over the first year after surgery. Best vision usually comes at least 6 to 18 months after surgery.
Penetrating Keratoplasty
Penetrating Keratoplasty (PK) involves replacing the entire, full thickness central-two-thirds of the cornea, leaving the peripheral portion intact. The transplanted tissue is held in place with between 16-24 sutures in the early healing phase. These sutures will be periodically removed by your doctor during the first year of healing. Best vision usually comes after at least six to 18 months.
OUR CORNEA SURGEONS
Saving Sight
We are proud to be a partner in sight with Saving Sight, a program of the Missouri Lions Eye Research Foundation.
Saving Sight retrieves, processes and distributes the highest quality donor eye tissue to corneal surgeons in the three-state region of Missouri, Kansas and Illinois before it’s offered to those nationally as well as internationally. We encourage our patients to write anonymous “thank you” notes that will be forwarded to the family of the donor.
Learn more about Saving Sight at saving-sight.org.
Our Cornea Transplant Team
Michelle Boyce, M.D.
Cornea, Cataract and Refractive Surgery
Yong Kam, M.D.
Cornea, Cataract and Refractive Surgery