Keratoconus With False Negative Findings On Curvature Map - OCULUS Pentacam Interpretation Manual

10 Screening for refractive surgery

10.11 Keratoconus with false negative findings on curvature map

This 4 Maps Selecable display (Figure 72) shows a classic keratoconus in OS. The anterior
elevation map shows a minor island that is still within the normal range. The posterior elevation,
however, shows a very significant area of inferior ectasia (positive island up to + 35 μm), and the
pachymetry map is significantly displaced and thinned to 499 μm. If the surgeon had only relied on
anterior curvature and central corneal thickness readings, this patient would have been classified
as normal (normal anterior curvature and central corneal thickness of 520 μm). This demonstrates
the importance of having accurate posterior elevation data in addition to anterior surface analysis.
DIAGNOSIS - form fruste or sub-clinical keratoconus, false negative on curvature
Figure 72: 4 Maps Selectable showing a form fruste keratoconus in OS with false
negative topography in the anterior curvature map
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