Maximum keratometry (Kmax)

Method

Steepest anterior corneal curvature value on the keratometric map by Scheimpflug tomography or Placido-disc topography, reported in diopters. The device is recorded on the edge - Pentacam and Orbscan values differ systematically and are not poolable.

The method is part of the endpoint identity. Studies measuring the same quantity by a different method are held as separate endpoints.

Notes

A single-point extremum and the standard progression criterion in keratoconus, where a rise of 1 diopter defines progression. Its near-miss is mean keratometry (Kmean) and simulated keratometry (SimK), read off the same scan at the same visit in the same diopter unit: those average a zone and therefore move far less, so an intervention that flattens the cone shows a large effect here and a near-null effect there, and substituting them understates efficacy. Distinct also from thinnest-point pachymetry and central corneal thickness, exported from the same tomography but measured in micrometres.