An endothelial keratoplasty is an alternative type of corneal transplant, a surgical procedure that removes the abnormal inner lining of the cornea, known as the endothelium, and replaces it with a donor cornea. The cornea is the clear covering of the front of the eye which bends, or refracts, light rays as they enter the eye. If the cornea is not shaped properly or is somehow clouded, whether because of injury, infection or disease, visual acuity is compromised, and a corneal transplant may be recommended. The three surgical methods of an endothelial keratoplasty include the following:
- Descemet's stripping and automated endothelial keratoplasty, known as DSAEK
- Descemet's stripping endothelial keratoplasty, known as DSEK
- Descemet's membrane endothelial keratoplasty, known as DMEK
The Endothelial Keratoplasty Procedure
During the endothelial keratoplasty procedure, the surgeon will make an incision in the sclera, the white part of the eye. This incision allows the surgeon to access the cornea, and remove the damaged endothelial tissue using a microkeratome blade, the same instrument that is used during LASIK surgery. The donor tissue is then folded and implanted inside the eye. After the donor tissue has been placed, it will either unfold on its own or be unfolded by the surgeon. An air bubble is injected to properly position the graft. This procedure is performed with a topical anesthetic to minimize any potential discomfort. The actual procedure takes up to 45 minutes to perform.
Penetrating (full thickness) Keratoplasty
Penetrating keratoplasty (PKP), also referred to as a corneal transplant or corneal graft, is the surgical removal of a damaged or diseased portion of the cornea, followed by the implantation of healthy tissue from a donated human cornea, which is usually obtained from an eye bank. The cornea is the clear covering of the front of the eye that refracts (bends) light rays as they enter the eye. If visual acuity is compromised because the cornea is not shaped properly or is clouded from injury, infection or disease, PKP may be recommended. The cornea has five layers; during PKP, all five layers are replaced with donor tissue.
The Penetrating Keratoplasty Procedure
The PKP procedure is performed, depending on the patient's age, condition and preference, under local or general anesthesia. Once the patient is anesthetized, a speculum is used to keep the eyelids open, and measurements are taken to assess how much donor tissue is needed. The damaged tissue is removed, and a matching portion of donor tissue is inserted in its place. The new tissue is stitched into place; stitches usually remain in place for many months up to a year. The surgery takes 1 to 2 hours, and is performed on an outpatient basis.
Deep Anterior Lamellar Keratoplasty (DALK)
Deep anterior lamellar keratoplasty, also known as DALK, is a corneal transplantation technique. It is used to remove the outermost layers of the cornea, while preserving the well-functioning inner layers known as Descemet's membrane and the endothelium. DALK is used in cases of anterior corneal opacifications, scars, and diseases such as keratoconus, in which the cornea has become badly misshapen.
The DALK Procedure
During this procedure, only the anterior layers of the central cornea are removed; the endothelial cells and Descemet's membrane are left in place. The surgeon bisects the cornea into two thin pieces, removing only the front, scarred portion. The damaged corneal tissue is replaced with donor tissue. Sutures are sometimes required. Because the DALK procedure is less invasive than a complete graft, the patient heals more quickly and is able to resume regular activities sooner.
Phototherapeutic Keratectomy (PTK)
Phototherapeutic keratectomy (PTK) is an advanced laser procedure used to treat corneal abnormalities by removing tissue from the cornea. Before the development of PTK, cornea treatment involved manually scraping away abnormal roughness with a surgical blade or replacing the entire cornea in a transplant procedure. PTK offers patients a safer, less invasive alternative that helps achieve the results they need. The PTK procedure is similar to photorefractive keratectomy (PRK) and may be performed together. PTK improves the overall health and shape of the cornea.
The Phototherapeutic Keratectomy Procedure
During the PTK procedure, the eye is numbed with anesthetic drops to reduce any potential discomfort. The eye is held open with a special device to prevent blinking during the procedure. The doctor will remove the epithelium, the protective covering of the cornea, from the eye, while using a laser to reshape the cornea to the eyes unique specifications, which have been pre-determined prior to the procedure. The laser procedure takes less than a minute to perform. The epithelium will heal naturally to cover the treated area.
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