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DESCRIPTIONA keratoprosthesis, consisting of a central optic held in a cylindrical frame, is an artificial cornea that is intended to restore vision to patients with severe bilateral corneal disease for which a corneal transplant is not an option, such as in cases involving prior failed corneal transplants, chemical injuries or certain immunological conditions. The keratoprosthesis replaces the cornea that has been removed and is held in place by the surrounding tissue. Various biologic materials are being investigated to improve integration of the prosthetic into the eye.
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 established surgical treatment for corneal disease is penetrating keratoplasty (PK), which involves making a large central opening through the cornea and then filling the opening with full-thickness donor cornea. In certain conditions such as Stevens-Johnson syndrome, cicatricial pemphigoid, chemical injury, or prior failed corneal transplant, survival of transplanted cornea is poor. The keratoprosthesis has been developed to restore vision in patients for whom a corneal transplant is not an option.
Keratoprosthetic devices consist of a central optic held in a cylindrical frame. The keratoprosthesis replaces the section of cornea that has been removed, and, along with being held in place by the surrounding tissue, may be covered by a membrane to further anchor the prosthesis. A variety of biologic materials are being investigated to improve the integration of prosthetic corneal implants into the stroma and other corneal layers.
The Dohlman-Doane Keratoprosthesis, most commonly referred to as the Boston Keratoprosthesis (KPro), is manufactured under the auspices of the Harvard Medical School‒affiliated Massachusetts Eye and Ear Infirmary. The Boston type I KPro uses a donor cornea between a central stem and a back plate. The Boston type II prosthesis is a modification of the type I prosthesis and is designed with an anterior extension to allow implantation through surgically closed eyelids. The AlphaCor, previously known as the Chirila keratoprosthesis (Chirila KPro) consists of a polymethylmethacrylate (PMMA) device with a central optic region fused with a surrounding sponge skirt; the device is inserted in a 2-stage surgical procedure.
Autologous keratoprostheses use a central polymethylmethacrylate (PMMA) optic supported by a skirt of either tibia bone or the root of a tooth with its surrounding alveolar bone. The most common is the osteo-odonto keratoprosthesis (OOKP), which uses osteodental lamina derived from an extracted tooth root and attached alveolar bone that has been removed from the patient’s jaw. Insertion of the OOKP device requires a complex staged procedure, in which the cornea is first covered with buccal mucosa. The prosthesis itself consists of a PMMA optical cylinder, which replaces the cornea, held in place by a biological support made from a canine tooth extracted from the recipient. A hole is drilled through the dental root and alveolar bone, and the PMMA prosthesis is placed within. This entire unit is placed into a subcutaneous ocular pocket, and then retrieved 6 to 12 months later for final insertion.
Hydroxyapatite, with a similar mineral composition to both bone and teeth (phosphate and calcium), may also be used as a bone substitute and as a bioactive prosthesis with the orbit. Collagen coating and scaffolds have also been investigated to improve growth and biocompatibility with the cornea epithelial cells, which form the protective layer of the eye. Many of these materials and devices are currently being tested in vitro or in animal models.
A keratoprosthesis is a Class II U.S. Food and Drug Administration (FDA) device intended to provide a transparent optical pathway through an opacified cornea, in an eye that is not a reasonable candidate for a corneal transplant. Two permanent keratoprostheses have received 510(k) marketing clearance by the FDA, the Boston KPro (Dohlman-Doane Keratoprosthesis) and the AlphaCor (Chirila keratoprosthesis). Both devices are indicated as permanent implantable keratoprostheses for eyes that are not corneal transplant candidates and are made of materials that have been proven to be biocompatible. According to the 510(k) summary, the AlphaCor keratoprosthesis was shown to be substantially equivalent to the Dohlman Doane Type I keratoprosthesis.
POLICYThe Boston Keratoprosthesis (Boston KPro) may be considered medically necessary for the treatment of corneal blindness under the following conditions:
Patients should be expected to be able to be compliant with postoperative care.
A permanent keratoprosthesis for all other conditions is considered investigational.
All other types of permanent keratoprostheses are considered investigational.
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 GUIDELINESImplantation of a keratoprosthesis is considered a high-risk procedure associated with numerous complications and probable need for additional surgery. Therefore, the likelihood of regaining vision and the patient’s visual acuity in the contralateral eye should be taken into account when considering the appropriateness of this procedure. Treatment should be restricted to centers experienced in treating this condition and staffed by surgeons adequately trained in techniques addressing implantation of this device.
Investigative service is defined as the use of any treatment procedure, facility, equipment, drug, device, or supply not yet recognized by certifying boards and/or approving or licensing agencies or published peer review criteria as standard, effective medical practice for the treatment of the condition being treated and as such therefore is not considered medically necessary.
The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.
POLICY HISTORY7/15/2004: Approved by Medical Policy Advisory Committee (MPAC)
10/1/2004: Code Reference section completed
5/24/2006: Policy reviewed, no changes
9/25/2007: Policy reviewed, permanent keratoprostheses changed to investigational. Removed "Permanent keratoprostheses may be considered medically necessary in adult patients with corneal opacity not suitable for standard penetrating keratoplasty with donor tissues, or where donor tissue has been declined, or where adjunctive measures required to prevent graft rejection are medically contraindicated."
06/22/2010: Policy description updated regarding treatment approaches and FDA approval of devices. Policy statement revised to indicate that the Boston keratoprosthesis (Boston KPro) may be considered medically necessary for the treatment of corneal blindness when specific criteria are met, and to state that a permanent keratoprosthesis for all other conditions and all other types of permanent keratoprostheses are considered investigational. FEP verbiage added to the Policy Exceptions section. Deleted outdated references in the Sources section. All codes moved from non-covered to covered, and added HCPCS code L8609.
04/20/2011: Policy reviewed; no changes.
03/27/2012: Policy reviewed; no changes.
04/17/2013: Policy reviewed; no changes.
03/18/2014: Policy reviewed; no changes.
07/08/2015: Policy description updated regarding devices. Medically necessary policy statement updated to add the following conditions: 1) Best-corrected vision is ≤20/400 in the affected eye and ≤20/40 in the opposite eye; AND 2) No end-stage glaucoma or retinal detachment is present; AND 3) The patient has one of the following indications: Multiple corneal transplant graft failures; Stevens-Johnson syndrome; Ocular cicatricial pemphigoid; Autoimmune conditions with rare ocular involvement; Ocular chemical burns; An ocular condition unlikely to respond favorably to primary corneal transplant surgery (eg, limbal stem cell compromise or postherpetic anesthesia).
SOURCE(S)Blue Cross Blue Shield Association policy # 9.03.01
CODE REFERENCEThis may not be a comprehensive list of procedure codes applicable to this policy.
The code(s) listed below are ONLY medically necessary if the procedure is performed according to the "Policy" section of this document.