April 15, 2014
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Corneal topography best method for diagnosing keratoconus, surgeon says

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The following is an excerpt from the Point/Counter column in the March 2014 issue of Ocular Surgery News APAO Edition:

What tool or method is best for diagnosing keratoconus?

POINT
From Peter S. Hersh, MD

I think that computerized corneal topography analysis remains the primary tool for diagnosing keratoconus. I use corneal topography to look for early changes in the corneal shape and optics. when looking at these maps, one can either use Placido-based or elevation-based topography, and there are a number of factors to look for: We look at asymmetry of astigmatism, both with regard to inferior-superior differences in steepness and irregularity of the astigmatic bowtie, as well as corneal steepening. Traditionally, a keratometry reading of 47 D or above is one possible indicator for keratoconus.

Elevation topography is also of use. In particular, when using height maps, the posterior elevation map is of particular importance because this may be one of the early indicators for diagnosing keratoconus. this may be more sensitive than the anterior sagittal height map because the anterior irregularity might be masked by the epithelium, which can smooth the anterior keratoconic irregularity. In addition, this type of topographer can produce pachymetry maps. Corneas where the thinnest area is off axis or in which the central cornea is relatively thin in relation to the periphery may also suggest keratoconus.

I do think we need a tool to measure corneal biomechanics. Keratoconus is, inherently, a disease of corneal structure and strength; so, an instrument to directly measure corneal biomechanical properties would be an indispensable tool for early detection of keratoconus. Read William J Dupps Jr.'s counter point