1. Post-Cataract Post-Transplant Corneal Surgery

   Aetna considers correction of surgically induced astigmatism with a corneal relaxing incision or corneal wedge resection medically necessary if the member had previous penetrating keratoplasty (corneal transplant) within the past 60 months or cataract surgery within the last 36 months and both of the following criteria are met:

   1. The degree of astigmatism must be 3.00 diopters or greater; and

   2. The member must be intolerant of glasses or contact lenses.

   Note: Correction of surgically induced astigmatism with a corneal relaxing incision or corneal wedge resection is covered when medical necessity criteria are met, even if the member's plan excludes refractive surgery.

2. Phototherapeutic Keratectomy

   Aetna considers phototherapeutic keratectomy (PTK) medically necessary for members with any of the following corneal conditions:

   1. Superficial corneal dystrophy (including granular, lattice, and Reis-Bückler's dystrophy); or
   2. Epithelial membrane dystrophy; or
   3. Irregular corneal surfaces due to Salzmann's nodular degeneration or keratoconus nodules; or
   4. Corneal scars and opacities (including post-traumatic, post-infectious, post-surgical, and secondary to pathology); or

   5. Recurrent corneal erosions when more conservative measures (e.g., lubricants, hypertonic saline, patching, bandage contact lenses, gentle debridement of severely aberrant epithelium) have failed to halt the erosions.

   Aetna considers PTK experimental and investigational for treatment of infectious keratitis and all other indications because it has not been shown to be safe and effective for these indications.

   Note: Phototherapeutic keratectomy (PTK) should not be confused with photorefractive keratectomy (PRK). Although technically the same procedure, PTK is used for the correction of particular corneal diseases, whereas PRK involves use of the excimer laser for correction of refractive errors (e.g., myopia, hyperopia, astigmatism, and presbyopia) in persons with otherwise non-diseased corneas.

3. Refractive Surgery

   Note: Aetna's standard HMO benefit plan excludes coverage of "radial keratotomy, including related procedures designed to surgically correct refractive errors." Traditional benefit plans generally exclude coverage for services "for or related to any eye surgery mainly to correct refractive errors." These exclusions apply to radial keratotomy (RK), astigmatic keratotomy, photorefractive keratectomy (PRK), photoastigmatic keratectomy (PARK), laser-in-situ keratomileusis (LASIK), keratomileusis, epikeratophakia, implantation of intrastromal corneal ring segments, and other refractive surgical procedures.

   For plans that do not have a specific contractual exclusion of refractive surgery, refractive surgery is considered investigational or not medically necessary, as is outlined below.

   For the U.S. Food and Drug Administration (FDA)-approved indications and indications accepted by the American Academy of Ophthalmology, refractive surgical procedures are considered not medically necessary, because spectacles or contact lenses have been shown to provide more accurate corrections of refractive errors than refractive surgery.

   1. Radial keratotomy (RK) is not considered medically necessary for treatment of myopia ranging from -2.00 to -8.00 diopters because this refractive error can be corrected satisfactorily with eyeglasses or contact lenses. Radial keratotomy is considered investigational for treatment of myopia greater than -8.00 diopters and it is also considered investigational for treatment of all other refractive errors.

   2. Astigmatic keratotomy (AK) (arcuate incision, corneal wedge resection) is considered medically necessary when performed for the correction of surgically induced astigmatism following medically indicated cataract removal or corneal transplant surgery. Astigmatic keratotomy is considered investigational for treatment of all other refractive errors. 

   3. Laser-in-situ keratomileusis (LASIK) is considered not medically necessary for treatment of myopia between -1.0 and -15.0 diopters, with or without astigmatism up to 5.0 diopters, because this can be corrected satisfactorily with eyeglasses or contact lenses. Laser-in-situ keratomileusis is also considered not medically necessary for treatment of hyperopia up to + 6.0 diopters with or without astigmatism up to 5 diopters. Laser-in-situ keratomileusis is considered investigational for treatment of myopia greater than -15.0 diopters or hyperopia greater than + 6.0 diopters, for treatment of persons with astigmatism greater than 5.0 diopters, and for all other refractive errors. This clinical policy is based on the FDA approved indications for LASIK.

   4. Standard keratomileusis (ALK) is considered investigational for treatment of all refractive errors.

   5. Epikeratoplasty (or epikeratophakia) is considered medically necessary for the following indications: 1) for the treatment of childhood aphakia since contact lenses are difficult for children to use and intraocular lens implants may result in long-term complications in children; 2) for the treatment of scarred corneas and corneas affected with endothelial dystrophy; 3) for the treatment of adult aphakia in circumstances where secondary implantation of an intraocular lens is not feasible because reentering the eye could affect outcome (e.g., vitreous in the anterior chamber, history of uveitis, disorganized anterior chamber that cannot support an intraocular lens, significant corneal endothelial disease, or gross corneal irregularity after trauma). This procedure is considered investigational for correction of refractive errors and for all other cases of adult aphakia. 

   6. Keratophakia is considered investigational for correction of refractive errors. 

   7. Lamellar keratoplasty (non-penetrating keratoplasty) is considered medically necessary for treatment of corneal diseases, including scarring, edema, thinning, distortion, dystrophies, degenerations, and keratoconus. It is considered investigational when performed solely to correct astigmatism and other refractive errors.

   8. Penetrating keratoplasty (PK) (corneal transplantation, perforating keratoplasty) is considered medically necessary for treatment of corneal diseases, including: 1) to improve poor visual acuity caused by an opaque cornea; 2) to remove active corneal disease, such as persistent severe bacterial, fungal, or amebic inflammation of the cornea (keratitis) after appropriate antibiotic therapy; 3) to restore altered corneal structure or to prevent loss of the globe that has been punctured: 4) to treat corneal diseases, including bullous keratopathy, keratoconus, corneal scar with opacity, keratitis, corneal transplant rejection, Fuch's dystrophy, corneal degeneration, other corneal dystrophies, corneal edema, and herpes simplex keratitis. Penetrating keratoplasty is considered investigational when performed solely to correct astigmatism or other refractive errors. Tissue procurement, preservation, storage and transportation associated with medically necessary corneal transplantation are also considered medically necessary.

   9. Photorefractive keratectomy (PRK) and Photoastigmatic keratectomy (PARK or PRK-A) are considered not medically necessary for patients with hyperopia of up to 6.0 diopters and myopia of up to -10.0 diopters, with or without astigmatism up to 4.0 diopters, because the refractive corrections achieved with PRK and PARK are less precise than that achieved by eyeglasses or contact lenses. Photorefractive keratectomy and PARK are considered investigational for patients with hyperopia greater than 6.0 diopters, myopia greater than -10.0 diopters, astigmatism greater than 4.0 diopters, and for all other refractive errors. This policy is based on the FDA approved indications for PRK and PARK. 

   10. Intrastromal corneal ring segments (INTACS) (Addition Technology, Sunnyvale, CA) are considered not medically necessary for adults with mild myopia (from -1.0 to -3.0 diopters) that have less than 1 diopter of astigmatism. Aetna considers intrastromal corneal ring segments experimental and investigational for children, for patients with moderate to severe myopia (greater than -3.0 diopters), for patients with more than 1 diopter of astigmatism, and for hyperopia. Intrastromal corneal ring segments are considered medically necessary for reduction or elimination of myopia or astigmatism in persons with keratoconus who are no longer able to achieve adequate vision using contact lenses or spectacles and for whom corneal transplant is the only remaining option.  Note: Where indicated for keratoconus, INTACS are not excluded from coverage under plans that exclude coverage of refractive surgery. Please check benefit plan descriptions.

   11. Conductive Keratoplasty is considered not medically necessary for treatment of patients who are at least 40 years of age, who have mild to moderate hyperopia (0.75 D to 3.25 D), who have 0.75 D or less astigmatism, and whose eyesight has changed very little over the previous 12 months (as demonstrated by a change of less than 0.50 D in refraction). Conductive keratoplasty is considered experimental and investigational for keratoconus and all other indications. 

   12. Methods of thermokeratoplasty other than conductive keratoplasty (see above), such as the superficial treatment of Gassett and Kaufman for keratoconus, holmium:YAG laser thermokeratoplasty (laser thermokeratoplasty or LTK), or the hot needle of Fyodorov, are considered experimental and investigational for treatment of refractive errors, keratoconus, and all other indications. 

   13. Orthokeratology is considered investigational for correction of refractive errors and all other indications. 

   14. Scleral Expansion Surgery is considered experimental and investigational for presbyopia and all other indications. 

   15. Intraocular lens implants (clear lens extraction) (aphakic intraocular lenses (IOLs)) are considered not medically necessary for correction of presbyopia, hyperopia, and myopia because these refractive errors can be corrected satisfactorily with eyeglasses or contact lenses. Intraocular lens implants are considered medically necessary for persons with aphakia (see CPB 508 - Cataract Removal Surgery.  

   16. Implantable contact lenses (without lens extraction) (phakic intraocular lenses (IOLs)) (e.g., Artisan lens, Verisye lens) are considered not medically necessary for myopia ranging from -5 to -20 diopters in persons with 2.5 diopters of astigmatism or less because external contact lenses or eyeglasses produce equivalent therapeutic results for treatment of refractive errors. Implantable contact lenses are considered experimental and investigational for other indications.

4. Coverage of Corneal Remodeling Surgery to Correct Refractive Errors in Plans that Explicitly Cover Refractive Surgical Procedures:

   Note: For members whose policies specifically include coverage for refractive surgery, refractive surgical procedures are covered for their FDA-approved indications and indications accepted by the American Academy of Ophthalmology (AAO), without regard to medical necessity. (The FDA-approved indications for refractive surgical procedures are listed in section III above.) Also, RK (which does not require FDA approval) is covered for indications recognized by the AAO as established -- mild to moderate myopia of -8.00 diopters or less. (See discussion of established indications for RK in section III above.) Aetna's payment for these services does not constitute any determination by Aetna that those services are medically necessary.

5. Keratoprosthesis (Artificial Cornea):

   Aetna considers keratoprosthesis experimental and investigational. 

6. Endothelial Keratoplasty:

   Aetna considers endothelial keratoplasty (Descemet's stripping endothelial keratoplasty (DSEK), Descemet's stripping automated endothelial keratoplasty (DSAEK),and Descemet's membrane endothelial keratoplasty (DLEK) medically necessary for the following indications in persons with endothelial failure and otherwise healthy corneas:

   1. Corneal edema;
   2. Bullous keratopathy;
   3. Rupture of Descemet's membrane;
   4. Endothelial corneal dystrophy and other posterior corneal dystropies;

   5. Mechanical complications due to corneal graft or ocular lens prostheses.

   Endothelial keratoplasty procedures are considered experimental and investigational for conditions with concurrent endothelial disease and anterior corneal disease, including anterior corneal dystrophies, anterior corneal scars from trauma or prior infection, ectatic conditions of the cornea such as keratoconus, pellucid marginal degeneration and ectasia after previous laser vision correction surgery, and for all other indications.

Refractive surgical procedures are considered by Aetna to be not medically necessary, because spectacles or contact lenses have been shown to provide more accurate corrections of refractive errors than refractive surgery. Although the efficacy of refractive surgery is improving, the accuracy and precision of the refractive corrections achieved is substantially less than that which can be achieved with spectacle correction. In a randomized prospective study of laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) for myopia, Hersh, et al. (1998) reported that 29.4% of PRK patients and 27.1% of LASIK patients had refractive corrections within 0.5 diopters of attempted correction at six months after surgery. In comparison, over 99% of patients who are corrected with glasses or contact lenses achieve refractive corrections within 0.5 diopters of normal vision (Waring, 1990).

Although the safety of refractive surgical procedures is improving, these procedures are associated with significant risks of degradation of best corrected visual acuity, as well as glare, induced regular or irregular astigmatism, regression of effect, visual aberrations (including transient or permanent glare or starburst/halo effect), and decreased contrast sensitivity. These optical complications and their incidence are discussed in a 1997 American Academy of Ophthalmology (AAO) Preferred Practice Pattern on Refractive Errors and a 1999 AAO Ophthalmic Procedures Assessment on PRK. According to the AAO Preferred Practice Pattern on Refractive Errors, "spectacles are the simplest and safest means of correcting a refractive error."

Radial keratotomy (RK) involves the use of radial incisions in the cornea to correct mild to moderate myopia. According to guidelines from the AAO, radial keratotomy has been shown to be effective for treatment of myopia ranging from -2.00 to -8.00 diopters. Radial keratotomy has not been proven to be effective for treatment of myopia greater than -8.00 diopters or for other refractive errors. The established indications for radial keratotomy were based on the 1992 AAO Ophthalmic Procedures Assessment of Radial Keratotomy for Myopia. The AAO's position on RK was reaffirmed in the 1997 AAO Preferred Practice Pattern on Refractive Errors, which restated that RK is indicated for "[l]ow to moderate myopia."

Astigmatic keratotomy (AK) (arcuate incision, corneal wedge resection) is a refractive surgical procedure similar to RK that is used to reduce astigmatism. Instead of radial incisions, a curvilinear pattern is used to smooth the areas of the cornea that are too steeply curved. In some instances, surgeons have combined RK with AK in patients with myopia with astigmatism. Variations of astigmatic keratotomy include the Ruiz Procedure and the Troutman Wedge Resection. Astigmatic keratotomy may be indicated for the correction of surgically induced astigmatism following medically indicated cataract removal or corneal transplant surgery. Astigmatic keratotomy has not been proven for treatment of other refractive errors. The 1997 AAO Preferred Practice Pattern on Refractive Errors states: "[T]here are few well-controlled, prospective clinical studies available on the procedure to date, performed either individually or in connection with other keratorefractive procedures."

Laser-in-situ keratomileusis (LASIK) is a type of laser surgery of the cornea to correct refractive errors, in which a slice of the patient's cornea is removed, shaped to the desired curvature with an excimer laser, and then sutured back to the remaining cornea. Laser-in-situ keratomileusis is approved by the FDA for treatment of myopia between -1.0 and -15.0 diopters, with or without astigmatism up to 5.0 diopters. Laser-in-situ keratomileusis has also been approved by the FDA for treatment of hyperopia up to + 6.0 diopters with or without astigmatism up to 5 diopters. Laser-in-situ keratomileusis has not been proven to be effective for treatment of myopia greater than -15.0 diopters or hyperopia greater than + 6.0 diopters, for treatment of persons with astigmatism greater than 5.0 diopters, and for other refractive errors.

Standard keratomileusis (ALK) where the cornea is shaped with a microkeratome rather than with a laser, has not been proven to be an effective treatment for refractive errors. The 1997 AAO Preferred Practice Pattern on Refractive Errors states "In its 1995 assessment on ALK, the American Academy of Ophthalmology identified a lack of peer-reviewed literature, although there are a number of studies ongoing. In current clinical practice, ALK is being replaced by laser in situ keratomileusis."

Epikeratoplasty (or epikeratophakia) is a refractive surgical procedure that involves placement of a pre-carved donor corneal lens on the surface of a patient's eye. Epikeratophakia may be indicated for the treatment of childhood aphakia since contact lenses are difficult for children to use and intraocular lens implants may result in long-term complications in children. This procedure may also be used on scarred corneas and corneas affected with endothelial dystrophy. In addition, although secondary implantation of an intraocular lens is the favored treatment of adult aphakia, there are circumstances where reentering the eye could affect outcome (e.g., vitreous in the anterior chamber, history of uveitis, disorganized anterior chamber that cannot support an intraocular lens, significant corneal endothelial disease, or gross corneal irregularity after trauma); in these cases of adult aphakia, epikeratophakia may be considered acceptable. This procedure is has not been proven to be effective for the correction of refractive errors and for all other cases of adult aphakia. The 1997 AAO Preferred Practice Pattern on Refractive Errors states that "[t]he results have been widely variable, and there have been significant complications. This procedure is not recommended for correction of myopic refractive errors, except in very unusual circumstances." This reaffirmed the 1995 AAO Ophthalmic Procedure Assessment of epikeratophakia.

Keratophakia involves implantation of a donor cornea within the corneal stroma to modify its refractive power. Keratophakia has not been proven to be effective for correction of refractive errors. Keratophakia was not addressed in the 1997 AAO Preferred Practice Pattern on Refractive Errors. However, an August 1992 AAO Ophthalmic Procedure Assessment of keratophakia concluded that they found only a "handful of reports" in peer-reviewed medical journals regarding keratophakia for correction of refractive errors, and few "well controlled studies." The AAO assessment raised questions about the safety and effectiveness of keratophakia. Since publication of the AAO's assessment, no additional clinical studies of keratophakia for refractive errors have been published, so the questions raised by that assessment remain unanswered.

Lamellar keratoplasty (non-penetrating keratoplasty) is a corneal transplant procedure in which a partial thickness of the cornea is removed and the diseased tissue is replaced with a partial-thickness donor cornea. The donor eye is prepared by making a partial thickness trephine incision in the cornea and dissecting free the lamellar button. This procedure may be indicated for a number of corneal diseases, including scarring, edema, thinning, distortion, dystrophies, degenerations, and keratoconus. It is has not been proven to be effective for correction of astigmatism and other refractive errors.

Penetrating keratoplasty (PK) (corneal transplantation, perforating keratoplasty) is a corneal transplant procedure involving replacement of the full thickness of the cornea with donor cornea, but retaining the peripheral cornea. As with lamellar keratoplasty, this procedure may be indicated for a number of corneal diseases. Most PKs are performed to improve poor visual acuity caused by an opaque cornea. Penetrating keratoplasty has also been used to remove active corneal disease, such as persistent severe bacterial, fungal, or amebic inflammation of the cornea (keratitis) after appropriate antibiotic therapy. Penetrating keratoplasty has also been performed to restore altered corneal structure or to prevent loss of the globe that has been punctured. The most common indications for PK are bullous keratopathy, keratoconus, corneal scar with opacity, keratitis, corneal transplant rejection, Fuch's dystrophy, corneal degeneration, other corneal dystrophies, corneal edema, and herpes simplex keratitis. Penetrating keratoplasty has not been proven to be effective for correcting astigmatism or other refractive errors.

Photorefractive keratectomy (PRK) is a refractive surgical procedure involving the reshaping of the surface of the cornea with an excimer laser to correct mild-to-moderate myopia. Photoastigmatic keratectomy (PARK or PRK-A) is a refractive surgical procedure to correct myopia with astigmatism. These procedures have been approved by the FDA for treatment of hyperopia of up to 6.0 diopters and myopia of up to -10.0 diopters, with or without astigmatism up to 4.0 diopters. Photorefractive keratectomy and PARK have not been proven effective for correction of hyperopia greater than 6.0 diopters, myopia greater than -10.0 diopters, astigmatism greater than 4.0 diopters, and other refractive errors.  A 1999 AAO Ophthalmic Procedures Assessment on PRK and PARK concluded that it "appears to be safe and effective procedure for the treatment of low to moderate degrees of myopia and astigmatism. Results for high degrees of myopia are associated with poorer outcomes, that is, longer stabilization periods, greater need for retreatment, and increased loss of lines of BSCVA [best spectacle corrected visual acuity]."

Phototherapeutic Keratectomy (PTK) is the same surgical procedure as PRK, but is used for the treatment of corneal diseases. PTK has been approved by the FDA to treat the following corneal conditions: 1) superficial corneal dystrophy (including granular, lattice, and Reis-Bückler's dystrophy); 2) epithelial membrane dystrophy; 3) irregular corneal surfaces due to Salzmann's nodular degeneration or keratoconus nodules; 4) corneal scars and opacities (including post-traumatic, post-infectious, post-surgical, and secondary to pathology); 5) recurrent corneal erosions when more conservative measures (e.g., lubricants, hypertonic saline, patching, bandage contact lenses, gentle debridement of severely aberrant epithelium) have failed to halt the erosions. PTK has not been proven to be effective for treatment of infectious keratitis or other diseases.  If used unilaterally PTK will induce a certain degree of anisometropia since it induces a shift in refraction to the hyperopic (farsighted) side. This hyperopic shift might be welcomed in myopes but may be problematic for emmetropes or low myopes.

Intrastromal corneal ring segments (INTACS) (Addition Technology, Sunnyvale, CA) have been approved by the FDA for adults with mild myopia (from -1.0 to -3.0 diopters) that have less than 1 diopter of astigmatism. Intrastromal corneal ring segments have not been proven to be effective in children, and for correction of moderate to severe myopia (greater than -3.0 diopters), for correction of refractive errors in persons with more than 1 diopter of astigmatism, and for correction of hyperopia. Intrastromal corneal ring segments have been approved by the FDA for reduction or elimination of myopia or astigmatism in persons with keratoconus who are no longer able to achieve adequate vision using contact lenses or spectacles and for whom corneal transplant is the only remaining option. INTACS involves inserting a flexible ring beneath the surface of the cornea to elevate the edge of the cornea. This effectively flattens the front of the eye, decreasing nearsightedness. Different size rings are used to correct different amounts of nearsightedness. Boxer Wachler, et al. (2003) reported on a retrospective study of 74 eyes of 50 persons who received INTACS implantation. The investigators found that the mean improvement in uncorrected visual acuity in persons with keratoconus who received INTACS was four lines of uncorrected visual acuity and two lines of best corrected visual acuity. The investigators also reported decreases in irregular astigmatism. In a prospective study involving 10 patients with keratoconus, Colin, et al. (2000) reported a 70 percent improvement in uncorrected visual acuity and a 50 percent improvement in best corrected visual acuity. INTACS was approved by the U.S. Food and Drug Administration (FDA) for use in keratoconus under a Humanitarian Device Exemption (HDE), as the FDA has determined that INTACS are a medical device intended to treat a condition that affects fewer than 4000 individuals per year in the United States (FDA, 2004). INTACS are approved for the reduction or elimination of myopia or astigmatism in persons with keratoconus, who are no longer able to achieve adequate vision with their contact lenses or spectacles, so that their functional vision may be restored and the need for corneal transplant procedure may potentially be postponed. According to the FDA, the specific subset of keratoconic patients proposed to be treated with INTACS prescription inserts are those who: 1) have experienced a progressive deterioration in their vision, such that they can no longer achieve adequate functional vision on a daily basis with their contact lenses or spectacles; 2) who are 21 years of age or older; 3) who have clear central corneas; 4) who have a corneal thickness of 450 microns or greater at the proposed incision site; and 5) who have corneal transplantation as the only remaining option to improve their functional vision (FDA, 2004).

Conductive Keratoplasty involves the application of radiofrequency thermal energy to increase the curvature of the cornea and thereby reduce hyperopia. Conductive keratoplasty using the ViewPoint CK System (Refractec Inc., Irvine, CA) has been approved by the FDA for treatment of patients who are at least 40 years of age, who have mild to moderate hyperopia (0.75 D to 3.25 D), who have 0.75 D or less astigmatism, and whose eyesight has changed very little over the previous 12 months (as demonstrated by a change of less than 0.50 D in refraction). Conductive keratoplasty has not been proven to be effective for correction of other refractive errors. According to the FDA, conductive keratoplasty temporarily improves distance vision in far-sighted people. Although some patients may retain some or all of the correction achieved during surgery, for most people the amount of farsightedness correction is temporary and will decrease over time. Vision without glasses is improved after conductive keratoplasty, but some people still need glasses or contact lenses. Since it corrects only farsightedness, CKSM does not eliminate the need for reading glasses. Conductive keratoplasty has not been proven to be effective as a treatment of keratoconus.

Methods of thermokeratoplasty other than conductive keratoplasty, such as the superficial treatment of Gassett and Kaufman for keratoconus, holmium:YAG laser thermokeratoplasty (laser thermokeratoplasty or LTK), or the hot needle of Fyodorov, have not been proven to be effective for the treatment of refractive errors or keratoconus. These methods of thermokeratoplasty have been abandoned because the corneal wound healing response produced postoperative scarring and instability (Waring, 1995).

Orthokeratology involves the application of sequentially flatter hard contact lenses to flatten the cornea and thereby reduce myopic refractive error. Orthokeratology has not been proven to be effective for the treatment of refractive errors. The AAO Preferred Practice Pattern on Refractive Errors states that "[a]ttempts to predict which patients will respond to orthokeratology based on ocular biomechanical or biometric parameters have not been successful. The effects of orthokeratology have been unpredictable and poorly controlled. … This approach is not recommended."

In an ophthalmic technology assessment performed for the AAO, Van Meter et al (2008) reviewed the published literature to evaluate the safety of overnight orthokeratology (OOK) for the treatment of myopia. Repeated searches of peer-reviewed literature were conducted in PubMed and the Cochrane Central Register of Controlled Trials for 2005, 2006, and 2007. The searches yielded 495 citations. The panel reviewed the abstracts of these articles and selected 79 articles of possible clinical relevance for review. Of these 79 full-text articles, 75 were determined to be relevant to the assessment objective. No study was rated as having level I evidence. Two pre-market applications to the FDA were rated as having level II evidence. There were 2 studies rated as having level II evidence. The main source of reports of adverse events associated with OOK was 38 case reports or non-comparative case series (level III evidence). The authors concluded that the prevalence and incidence of complications associated with OOK have not been determined. Complications, including more than 100 cases of infectious keratitis resulting from gram-positive and gram-negative bacteria and Acanthamoeba, have been described in case reports and case series representing observations in undefined populations of OOK users. Data collection was non-standard. Risk factors for various complications can not be determined. Because OOK puts patients at risk for vision-threatening complications they may not encounter otherwise, sufficiently large well-designed cohort or randomized controlled studies are needed to provide a more reliable measure of the risks of treatment and to identify risk factors for complications. These investigators also stated that OOK for slowing the progression of myopia in children also needs well-designed and properly conducted controlled trials to examine its effectiveness. Because of variations in orthokeratology practice, a wide margin of safety should be built into OOK regimens.

Scleral Expansion Surgery has not been proven to be effective for treatment of presbyopia. Scleral expansion surgery involves making small incisions in the eye and inserting bands to stretch the part of the sclera that lies beneath the ciliary muscles that control accommodation (NICE, 2004). This procedure is claimed to improve accommodation. An assessment of scleral expansion surgery by the National Institute for Clinical Excellence (2004) recommended that "this procedure should not be used." Based on an assessment of available published evidence, the assessment concluded that "[c]urrent evidence on the safety and efficacy of scleral expansion surgery for presbyopia is very limited" and that "[a]ll studies identified were of poor quality." The assessment explained that "[t]here is no evidence of efficacy in the majority of patients" and that "[t]here are also concerns about the potential risks of the procedure."

Glasser (2008) noted that a variety of surgical procedures has been considered for restoring accommodation to the presbyopic eye, including surgical expansion of the sclera, using femtosecond lasers to treat the lens or with so-called accommodative IOLs. The author stated that evidence suggests that scleral expansion can not and does not restore accommodation. 

Intraocular lens implants (clear lens extraction) (aphakic intraocular lenses (IOLs)) have been approved by the FDA for correction of presbyopia, hyperopia, and myopia. Clear lens extraction is similar to cataract removal surgery in that the natural lens is removed and replaced with an intraocular lens.

Implantable contact lenses (without lens extraction) (phakic intraocular lenses (IOLs)) (e.g., Artisan lens, Verisye lens) have been approved by the FDA for adult patients who have myopia ranging from -5 to -20 diopters with less than or equal to 2.5 diopter of astigmatism. Implantable contact lenses have not been proven to be effective for other indications.

Keratoprosthesis have not been proven to be effective. Some patients cannot undergo the standard penetrating keratoplasty using donor tissue for several reasons (e.g., disease severity, severe involvement of the conjunctiva, objection to the use of donor tissue, failed past donor tissue transplants, or when measures required to prevent graft rejection are medically contraindicated). For these individuals, penetrating keratoplasty using a keratoprosthesis has been employed as an alternative. However, the clinical value of this prosthesis has not been established. The Alberta Heritage Foundation for Medical Research (AHFMR, 2001) noted that there is inadequate evidence to prove the safety and effectiveness of any keratoprosthesis model, and as keratoprosthesis models keep evolving, these new versions have not yet been proven in human trials with sufficient follow-up and patient numbers. The AHFMR further stated that "currently there is no consensus in the literature on optimal device and implantation techniques, and no accepted standard for this procedure. In general, keratoprosthesis surgery is complicated, has a narrow safety margin, and requires intensive follow-up, thus a conservative approach is currently recommended by the eye specialists in this area". Furthermore, Alio and colleagues (2004) reported that corneal keratoprosthesis (BIOKOP I, II) did not provide a stable anatomical relation with the surrounding ocular structures. Its ability to restore vision is limited to a short post-operative period in eyes implanted with severe ocular surface disease. Additionally, the National Institute of Clinical Excellence (Dillon, 2004) stated that current evidence on the safety and efficacy of insertion of hydrogel keratoprosthesis does not appear adequate for this procedure to be used without special arrangements for consent and for audit or research.

Tan et al (2008) established a multi-disciplinary surgical program for osteo-odonto-keratoprosthesis (OOKP) surgery in Asia and evaluated the safety and effectiveness of this keratoprosthesis in end-stage corneal and ocular surface disease. A total of 16 adults of Asian ethnic origin, bilaterally blind with end-stage corneal blindness from Stevens-Johnson syndrome, or severe chemical or thermal burns were included in this study. Osteo-odonto-keratoprosthesis surgery involves 2 procedures-in stage 1, an autologous canine tooth is removed, modified to receive an optical polymethyl methacrylate cylinder, and implanted into the cheek. The ocular surface is denuded and replaced with full-thickness buccal mucosa. Stage 2 surgery, performed 2 to 4 months later, involved retrieval of the tooth-cylinder complex and implanting it into the cornea, after reflection of the buccal mucosal flap, corneal trephination, iris and lens removal, as well as anterior vitrectomy. Concurrent glaucoma and vitreoretinal procedures were also performed at either stage, as required. Main outcome measures included visual acuity (VA), field of vision, anatomical integrity and stability, as well as ocular and oral complications related or unrelated to the OOKP device. Osteo-odonto-keratoprosthesis surgery was performed on 15 patients, with a mean follow-up of 19.1 months (range of 5 to 31). Intra-operative complications included expulsive hemorrhage (keratoprosthesis device not implanted), tooth fracture (n = 1), oronasal fistula (n = 1), and mild inferior optic tilt (n = 1). Anatomical stability and keratoprosthesis retention has been maintained in all eyes, with no dislocation, extrusion, retro-prosthetic membrane formation, or keratoprosthesis-related infection. Other complications not directly related to device insertion included retinal detachment (RD) related to silicone oil removal (n = 1) and endophthalmitis related to endoscopic cyclophotocoagulation performed 1 year after OOKP surgery (n = 1). Eleven patients (73.3 %) attained a stable best spectacle-corrected VA of at least 20/40 or better, whereas 9 (60 %) attained stable 20/20 vision. Four patients achieved their best visual potential, ranging from 20/100 to counting fingers vision, related to pre-existing glaucomatous optic neuropathy or previous RD. The authors concluded that establishment of their OOKP program suggested that OOKP surgery has the potential to restore good vision to the most severe cases of corneal blindness in an Asian setting, with minimal device-related complications. They stated that longer follow-up (5 years) of these cases is currently underway.

Descemet's stripping automated endothelial keratoplasty (DSAEK) is being investigated as a treatment for corneal endothelial dysfunction. The procedure employs a mechanical microkeratome to harvest the donor corneal lenticule and mechanical stripping of the diseased host endothelium and Descemet's membrane. It has been used to treat corneal dysfunction associated with Fuchs' endothelial dystrophy, bullous keratopathy, irido-corneal endothelial syndrome or a failed penetrating graft. Koenig and Covert (2007) reported their early results of DSAEK (n = 26). They found that despite a smooth graft-host interface, only 2 subjects achieved greater than or equal to 20/25 vision. The average visual results were comparable to vision after deep lamellar endothelial keratoplasty. Although patients experienced excellent post-operative acuity with minimally induced surgical astigmatism, nearly one third of the donor lenticules needed to be either re-positioned or replaced.

In a prospective study (n = 9), Mearza and colleagues (2007) reported their clinical experience and 12-month findings of DSAEK. They concluded that DSAEK provided excellent refractive and reasonable visual outcomes in this limited series, but there were frequent problems with dislocation of the donor tissue, and the graft failure rate was high. The graft failures may be linked to excessive endothelial damage, and the high dislocation rate may be linked to not filling the anterior chamber totally with air after insertion of the donor. They stated that further development of the procedure is needed. Additionally, Price and Price (2007) noted that continued evolution of this relatively new technique will aid to reduce complications and further improve outcomes.

In a retrospective observational case series, Oster et al (2008) characterized the clinical and histological features of primary graft failure after DSAEK. A total of 16 cases of DSAEK graft failure from 15 patients, all with detailed histological examination of failed graft tissue were included in this study. Hematoxylin-eosin, periodic acid-Schiff staining, and light microscopy were used to examine the failed DSAEK graft tissue from all patients. Main outcome measures included examination of specimens for corneal endothelial cell viability and host-donor interface characteristics. Clinical history revealed that 88 % (14/16) of studied DSAEK grafts detached before failure, and pathological examination found that 75 % (12/16) of failed grafts had atrophic corneal endothelium. Examples of residual host Descemet's membrane in the graft site and improper donor trephination were also identified. The authors concluded that marked loss of the corneal endothelium is the prominent feature of primary DSAEK graft failure. Examples of surgical features, such as incomplete Descemet's stripping and residual full-thickness cornea with a DSAEK graft, were shown.

In a position paper, the American Academy of Ophthalmology (2009) explains that endothelial keratoplasty procedures offer an alternative to penetrating keratoplasty to replace diseased endothelium with healthy donor tissue, without the need to remove the entire cornea. Introduced in 1988, deep lamellar endothelial keratoplasty (DLEK), which involves the creation of a deep lamellar pocket and replacement of posterior stroma with healthy donor tissue, allowed more rapid visual rehabilitation and a smaller incision than penetrating keratoplasty, but it was difficult to learn and time consuming. Descemet's stripping endothelial keratoplasty (DSEK) was introduced in 2005, and Descemet's stripping automated endothelial keratoplasty (DSAEK) was introduced in 2006; these procedures have supplanted DLEK. These methods for EK involve removal of Descemet's membrane and endothelium and replacement with donor tissue. When donor tissue is comprised of Descemet's membrane and endothelium alone, the technique is known as Descemet's membrane endothelial keratoplasty (DMEK). The AAO position paper states that endothelial keratoplasty procedures are associated with a smaller incision and faster visual rehabilitation than penetrating keratoplasty. The position paper states that there remain concerns about potential complications and long-term efficacy of endothelial keratolasty, including concerns about graft dislocations, endothelial cell los, and failed grafts. The AAO position paper cites the conclusions of an AAO Technology Assessment, which acknowledge the relatively short-term follow up and varying surgical techniques in the literature, but states "there is no evidence that DSAEK carriers unacceptable risks for surgical treatment of endothelial corneal disease. In comparison to PK, DSAEK appears at least equivalent in terms of safety, efficacy, surgical risks, and complictions rates and superior to PK in terms of refractive stability, postoperative refractive outcomes, wound and suture-related complications, and intraoperative choroidal hemorrhage risk."

An assessment of endothelial keratoplasty by the National Institute for Health and Clinical Excellence (NICE, 2008) found adequate evidence to support the use of this procedure.  The NICE assessment cited comparative studies which found better visual acuity and a lower incidence of astigmatism with endothelial keratoplasty compared with penetrating keratoplasty. The specialist advisors to NICE listed adverse events of endothelial keratoplasty reported in the literature or anecdotally as graft dislocation, graft failure and rejection, interface opacification, and loss of best spectacle corrected visual acuity.