The spatial variation in thickness for the horizontal meridian of eighteen keratoconic corneas was measured with the aid of a pachometer and a new automatic recording system. The significance of these measurements is discussed in relation to the results of standard clinical tests, moiré keratometry, small-mire keratometry and photokeratoscopy.
Mandell RB, Polse KA. Keratoconus: Spatial Variation of Corneal Thickness as a Diagnostic Test. Arch Ophthalmol. 1969;82(2):182–188. doi:10.1001/archopht.1969.00990020184006