Corneal Topography/Computer-Assisted Photokeratoscopy
Computer assisted corneal topography (also called photokeratoscopy or videokeratography) provides a quantitative measure of corneal curvature. Measurement of corneal topography is being evaluated to aid the diagnosis and followup of corneal disorders such as keratoconus, difficult contact lens fits, and pre- and postoperative assessment of the cornea, most commonly after refractive surgery. Various techniques and instruments are available to measure corneal topography:
The keratometer (ophthalmometer), the most commonly used instrument, projects an illuminated image onto a central area in the cornea. The fact that the keratometer can only estimate the corneal curvature over a small percentage of its surface, and that estimates are based on the frequently incorrect assumption that the cornea is spherical, are limitations of this technique.
The keratoscope is an instrument that reflects a series of concentric circular rings off the anterior corneal surface. Visual inspection of the shape and spacing of the concentric rings provides a qualitative assessment of topography. A photokeratoscope is a keratoscope equipped with a camera, which can provide a permanent record of the corneal topography.
Computer-assisted photokeratoscopy is an alternative to keratometry or keratoscopy in measuring corneal curvature. This technique uses sophisticated image analysis programs to provide quantitative corneal topographic data.
An evaluation of corneal topography for the accurate diagnosis and follow-up of certain corneal disorders, such as keratoconus, is considered medically necessary.
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American Academy of Ophthalmology. (2012). Refractive errors & refractive surgery Preferred Practice Pattern. Retrieved September 16, 2015 from http://www.aao.org.
BlueCross BlueShield Association, Medical Policy Reference Manual. (3:2017). Corneal topography / Computer-assisted Corneal Topography / Photokeratoscopy (9.03.05). Retrieved June 5,2017 from BlueWeb. (6 articles and/or guidelines reviewed)
BlueCross BlueShield of Tennessee network physicians. June-July 2011.
First Coast Service Options, Inc. (2016, August) Local Coverage Determination (LCD): Computerized Corneal Topography (L33810) Retrieved June 5, 2017 from: https://www.cms.gov.
U. S. Food and Drug Administration (1999, March) Center for Devices and Radiologic Health. 510(k) Premarket Notification Database K984443 (Orbscan II™) Retrieved June 5, 2017 from www.fda.gov.
ORIGINAL EFFECTIVE DATE: 12/14/1998
MOST RECENT REVIEW DATE: 7/13/2017
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