Corneal Topography, Computer Assisted Photokeratoscopy
© Blue Cross and Blue Shield of Montana
Current Effective Date:
February 01, 2014
Original Effective Date:
August 05, 1999
January 15, 2014
June 25, 2002; March 1, 2005, November 7, 2011; August 31, 2012; October 24, 2013; January 15, 2014
Computer-assisted topography/photokeratoscopy provides a quantitative measure of corneal curvature. Measurement of corneal topography is being evaluated for the diagnosis and follow-up of corneal disorders such as keratoconus, difficult contact lens fits, and pre- and postoperative assessment of the cornea, most commonly after refractive surgery.
Corneal topography describes measurements of the curvature of the cornea. An evaluation of corneal topography is necessary for the accurate diagnosis and follow-up of certain 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 (also referred to as an ophthalmometer), the most commonly used instrument, projects an illuminated image onto a central area in the cornea. By measuring the distance between a pair of reflected points in both of the cornea’s two principal meridians, the keratometer can estimate the radius of curvature of two meridians. 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 that 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. Early computer-based programs were combined with keratoscopy to create graphic displays and high-resolution color-coded maps of the corneal surface. Newer technologies measure both curvature and shape, enabling quantitative assessment of corneal depth, elevation, and power.
A number of devices have received clearance for marketing through the U.S. Food and Drug Administration (FDA) 510(k) mechanism. The Orbscan® (manufactured by Orbtek and distributed by Bausch and Lomb) received FDA clearance in 1999. The second generation Orbscan II is a hybrid system that uses both projective (slit scanning) and reflective (Placido) methods. The Pentacam® (Oculus) is one of a number of rotating Scheimpflug imaging systems produced in Germany.
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Not medically necessary for all diagnoses.
Not medically necessary for all diagnoses.
- Morrow GL, Stein RM. Evaluation of corneal topography: past, present and future trends. Can J Ophthalmol 1992; 27(5):213–25.
- Wilson SE, Klyce SD. Advances in the analysis of corneal topography. Surv Ophthalmol 1991; 35(4-Jan):269–77.
- Bhatoa NS, Hau S, Ehrlich DP. A comparison of a topography-based rigid gas permeable contact lens design with a conventionally fitted lens in patients with keratoconus. Cont Lens Anterior Eye 2010; 33(3):128-35.
- Lee H, Chung JL, Kim EK et al. Univariate and bivariate polar value analysis of corneal astigmatism measurements obtained with 6 instruments. J Cataract Refract Surg 2012; 38(9):1608-15.
- Ophthalmic Technology Assessment Committee Cornea Panel American Academy of Ophthalmology. Corneal topography. Ophthalmology 1999; 106(8-Jan):1628-38.
- Corneal Topography/Computer-Assisted Corneal Topography/Photokeratoscopy. Chicago, Illinois: Blue Cross Blue Shield Association Medical Policy Reference Manual (2013 April) Other 9.03.05.
||Policy revised: Policy statement change from medically necessary criteria to strictly not medically necessary for computer assisted corneal topography/photoderatoscopy. Name change from Corneal Topagraphy to Corneal Topography/Computer-Assisted Corneal Topography/Photokeratoscopy|
||Policy updated with literature review through February 2012; policy statement unchanged|
||Policy formatting and language revised. Policy statement unchanged. Title changed from "Corneal Topography/Computer-Assisted Corneal Topography/Photokeratoscopy" to "Corneal Topography, Computer Assisted Photokeratoscopy". Added category III code 0181T and removed codes 76514 and S0820.|
||Document updated with literature review. Coverage unchanged.|