Fig 1. Cumulative distribution of sensation thresholds to selective stimulation of the central cornea in control subjects and keratoconus patients.

(A) air pulses of increasing flow (mechanical stimulation), (B) pulses with increasing CO₂ concentration (chemical stimulation), (C) pulses of air at increasing temperatures (hot thermal stimulation), and (D) pulses of air at decreasing temperatures (cold thermal stimulation), in KC patients (gray line) and controls (black line).