Surgery Section - Phototherapeutic Keratectomy

IMPORTANT REMINDER

This Medical Policy has been developed through consideration of medical necessity, generally accepted standards of medical practice, and review of medical literature and government approval status.

Benefit determinations should be based in all cases on the applicable contract language. To the extent there are any conflicts between these guidelines and the contract language, the contract language will control.

The purpose of medical policy is to provide a guide to coverage. Medical Policy is not intended to dictate to providers how to practice medicine. Providers are expected to exercise their medical judgment in providing the most appropriate care.

Description

Phototherapeutic keratectomy involves the use of the excimer laser to treat visual impairment or irritative symptoms relating to diseases of the anterior cornea by sequentially ablating uniformly thin layers of corneal tissue. Phototherapeutic keratectomy may be performed in the office setting using topical anesthesia. Phototherapeutic keratectomy must be distinguished from photorefractive keratectomy, which involves the use of the excimer laser to correct refractive errors of the eye (e.g., myopia, astigmatism, hyperopia, and presbyopia). Photorefractive keratectomy is addressed in a separate policy (see cross reference).

Essentially, phototherapeutic keratectomy (PTK) functions by removing anterior stromal opacities or eliminating elevated corneal lesions while maintaining a smooth corneal surface. Complications of PTK include refractive errors, most commonly hyperopia, corneal scarring, and glare. The U.S. Food and Drug Administration (FDA) labeling for the excimer laser identifies the following ophthalmologic therapeutic indications:

1. Superficial corneal dystrophies (including granular, lattice, and Reis-Buckler’s dystrophies)
2. Epithelial basement membrane dystrophy, irregular corneal surfaces (secondary to Salzmann’s degeneration, keratoconus nodules or other irregular surfaces)
3. Corneal scars and opacities (due to trauma, surgery, infection and pathology).

Although not included in the FDA labeling, there has been interest in PTK as a treatment of recurrent corneal erosions in patients who have not responded to conservative therapy with patching, cycloplegia, topical antibiotics, and lubricants.

When PTK is used to remove only the epithelial surface of the cornea, the alternative technology is mechanical superficial keratectomy, i.e., corneal scraping. When PTK is used to remove deeper layers of the cornea, (extending into Bowman’s layer), competing technologies include lamellar keratoplasty. Candidates for PTK should first exhaust medical approaches. For example, recurrent corneal erosions can be treated conservatively with lubricants, patching, bandage contact lenses, or anterior stromal punctures, while keratoconus can be treated with rigid contact lenses to correct the astigmatism.

Policy/Criteria

1. Phototherapeutic keratectomy may be considered medically necessary when used as an alternative to a lamellar keratoplasty in the treatment of visual impairment or irritative symptoms related to corneal scars, opacities, or dystrophies extending beyond the epithelial layer.
2. Phototherapeutic keratectomy is considered not medically necessary when used as an alternative to a superficial mechanical keratectomy in treating patients with superficial corneal dystrophy, epithelial membrane dystrophy, and irregular corneal surfaces due to Salzmann’s nodular degeneration or keratoconus nodules.
3. Investigational applications of phototherapeutic keratectomy include, but are not limited to, treatment of recurrent corneal erosions and infectious keratitis.

Scientific Background

There are no controlled clinical studies that have directly compared PTK with other forms of treatment, including superficial keratectomy (used to treat superficial lesions) or lamellar keratoplasty (used to treat deeper lesions) or anterior stromal puncture (used to treat recurrent corneal erosions). The FDA approval was based on data from uncontrolled trials of patients with a variety of corneal pathologies. For example, Summit Technology presented data on 398 eyes, including 103 eyes with dystrophy (25.9%), 64 eyes with recurrent erosion (16.1%), and 231 eyes with scars, opacities, or other irregular surfaces (58%). (2) Outcomes included best-corrected visual acuity and/or decrease in irritative symptoms, such as pain and discomfort. Among cases undergoing PTK to increase comfort, 88.5% were considered successes at one year. Among those with visual impairment, 63.4% were considered successes. The most common adverse effect was corneal scarring and glare, occurring in 13.7% and 12.2% of cases, respectively. The results of this trial have also been summarized by Maloney and colleagues. (3)

Superficial mechanical keratectomy is regarded as a minimally invasive, safe and effective procedure to remove the superficial layer of the cornea. While PTK offers a more precise and elegant method of epithelial removal, there have been no controlled studies that have demonstrated that this technological superiority results in an improved patient health benefit. The precision of PTK may be most significant when deeper corneal lesions involving Bowman's layer are present. In this situation, PTK represents a minimally invasive alternative to lamellar keratoplasty.

An updated MEDLINE search through January 8, 2008 identified no additional published data which alter the conclusions reached above.

References

1. BlueCross BlueShield Association Medical Policy Reference Manual, Policy No. 9.03.07
2. Summit Technology, Inc., Summary of Safety and Receptiveness Data, excised ExciMed UV200LA or SVS Apex (formerly the OmniMed) Excimer Laser System for Phototherapeutic Keratectomy (PTK). Waltham, MA: Summit Technology, Inc. 1995
3. Maloney RK, Thompson V, Ghisell G et al. A prospective multicenter trial of excimer laser phototherapeutic keratectomy for corneal vision loss. Am J Ophthalmol 1996;122(2):149-60

Cross References

Implantation of Intrastromal Corneal Ring Segments, Regence Medical Policy Manual, Surgery, Policy No. 126

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