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DESCRIPTIONEndothelial keratoplasty (EK), also referred to as posterior lamellar keratoplasty, is a form of corneal transplantation in which the diseased inner layer of the cornea, the endothelium, is replaced with healthy donor tissue. Specific techniques include Descemet’s stripping endothelial keratoplasty, Descemet’s stripping automated endothelial keratoplasty, or Descemet’s membrane endothelial keratoplasty.
The cornea, a clear, dome-shaped membrane that covers the front of the eye, is a key refractive element of the eye. Layers of the cornea consist of the epithelium (outermost layer); Bowman’s layer; the stroma, which comprises approximately 90% of the cornea; Descemet’s membrane; and the endothelium. The endothelium removes fluid from the stroma and limits its entry, thereby maintaining the ordered arrangement of collagen and preserving the cornea’s transparency. Diseases that affect the endothelial layer include Fuchs’ endothelial dystrophy, aphakic and pseudophakic bullous keratopathy (corneal edema following cataract extraction), and failure or rejection of a previous corneal transplant.
The established surgical treatment for corneal disease is penetrating keratoplasty (PK), which involves the creation of a large central opening through the cornea and then filling the opening with full-thickness donor cornea that is sutured in place. Visual recovery after PK may take a year or more due to slow wound healing of the avascular full-thickness incision, and the procedure frequently results in irregular astigmatism due to the sutures and the full-thickness vertical corneal wound. PK is associated with an increased risk of wound dehiscence, endophthalmitis, and total visual loss after relatively minor trauma for years after the index procedure. There is also risk of severe, sight-threatening complications such as expulsive suprachoroidal hemorrhage, in which the ocular contents are expelled during the operative procedure, as well as postoperative catastrophic wound failure.
A number of related techniques have been, or are being, developed to selectively replace the diseased endothelial layer. One of the first endothelial keratoplasty (EK) techniques was termed deep lamellar endothelial keratoplasty (DLEK), which used a smaller incision than PK, allowed more rapid visual rehabilitation, and reduced postoperative irregular astigmatism and suture complications. Modified EK techniques include endothelial lamellar keratoplasty, endokeratoplasty, posterior corneal grafting, and microkeratome-assisted posterior keratoplasty. Most frequently used at this time are Descemet’s stripping endothelial keratoplasty (DSEK), which uses hand-dissected donor tissue, and Descemet’s stripping automated endothelial keratoplasty (DSAEK), which uses an automated microkeratome to assist in donor tissue dissection. These techniques include some donor stroma along with the endothelium and Descemet’s membrane, which results in a thickened stromal layer after transplantation. If the donor tissue comprises Descemet’s membrane and endothelium alone, the technique is known as Descemet’s membrane endothelial keratoplasty (DMEK). By eliminating the stroma on the donor tissue and possibly reducing stromal interface haze, DMEK is considered to be a potential improvement over DSEK/DSAEK.
EK involves removal of the diseased host endothelium and Descemet’s membrane with special instruments through a small peripheral incision. A donor tissue button is prepared from corneoscleral tissue after removing the anterior donor corneal stroma by hand (e.g., DSEK) or with the assistance of an automated microkeratome (e.g., DSAEK). Several microkeratomes have received clearance for marketing through the U.S. Food and Drug Administration (FDA) 510(k) process. Donor tissue preparation may be performed by the surgeon in the operating room, or by the eye bank and then transported to the operating room for final punch out of the donor tissue button. To minimize endothelial damage, the donor tissue must be carefully positioned in the anterior chamber. An air bubble is frequently used to center the donor tissue and facilitate adhesion between the stromal side of the donor lenticule and the host posterior corneal stroma. Repositioning of the donor tissue with application of another air bubble may be required in the first week if the donor tissue dislocates. The small corneal incision is closed with one or more sutures, and steroids or immunosuppressants may be provided either topically or orally to reduce the potential for graft rejection. Visual recovery following EK is typically achieved in 4-8 weeks, in comparison with the year or more that may be needed following PK.
Eye Bank Association of America (EBAA) statistics show the number of EK cases in the United States increased from 1,398 in 2005 to 14,159 in 2007. About 1/3 of corneal transplants performed in the United States were EK procedures, and EK was performed for over 85% of patients with endothelial disease.
As with any new surgical technique, questions have been posed about long-term efficacy and the risk of complications. EK-specific complications include graft dislocations, endothelial cell loss, and rate of failed grafts. Also of interest is the impact of the surgeon’s learning curve on the risk of complications.
Indications for Keratoprosthesis are discussed in a separate policy.
POLICYEndothelial keratoplasty (Descemet’s stripping endothelial keratoplasty or Descemet’s stripping automated endothelial keratoplasty) may be considered medically necessary for the treatment of endothelial dysfunction, including but not limited to Fuchs’ endothelial dystrophy, aphakic and pseudophakic bullous keratopathy, and failure or rejection of a previous corneal transplant.
POLICY EXCEPTIONSFederal Employee Program (FEP) may dictate that all FDA-approved devices, drugs or biologics may not be considered investigational and thus these devices may be assessed only on the basis of their medical necessity.
POLICY GUIDELINESThe coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member’s specific benefit plan language.
POLICY HISTORY10/13/2009: Policy added
11/19/2009: Approved by MPAC
09/09/2010: Policy reviewed; policy statement unchanged. FEP verbiage added to the Policy Exceptions section.
09/28/2011: Policy reviewed; no changes.
09/27/2012: Policy reviewed; no changes.
SOURCESBlue Cross Blue Shield Association Policy # 9.03.22
CODE REFERENCEThis is not intended to be a comprehensive list of codes. Some covered procedure codes have multiple descriptions.
The code(s) listed below are ONLY covered if the procedure is performed according to the "Policy" section of this document.