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Although topography is still the ideal diagnostic tool for the detection or confirmation of
keratoconus (especially forme fruste or subclinical keratoconus), there are several other clinical
observations that could help guide you to a diagnosis of keratoconus. Keep in mind that some of these
methods are better known than others; however, each one is surprisingly accurate in facilitating a
potential diagnosis of keratoconus and substantiating a need for a topography measurement:
- Steep keratometry readings (i.e., > 47.00D).
- A notable difference in pachymetry as you move towards the peripheral cornea. In a healthy cornea, the
more peripheral you measure, the thicker the cornea. However, if the peripheral cornea (inferior) is not at
least 20µm thicker, this raises suspicion for keratoconus.
- A difference of >1.00D of astigmatism between the two eyes. Because keratoconus is an asymmetric,
progressive condition, it's not uncommon for one eye to progress faster than the other. And because corneal
irregularity, such as astigmatism, is characteristic of keratoconus, a difference of > 1.00D of astigmatism
is a potential indicator.
- An unstable refractive error.
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