Table 1. The diagnostic cutoff criteria for evaluated pachymetric factors.

Parameter	Higher-specificity cutoffs (based on 2SD), higher chance of false negative		Higher-sensitivity cutoffs (based on 1SD), higher chance of false positive
	2.5% chance of not being a keratoconus suspect or keratoconic	2.5% chance of not being keratoconic	16% chance of not being a keratoconus suspect or keratoconic	16% chance of not being keratoconic
Central corneal thickness (CCT) (μm)	<476.2	<444.4	<514.2	<491.6
Minimum corneal thickness (MCT) (μm)	<460.7	<425.2	<499.8	<474.4
Difference between central and minimum corneal thickness (μm)	>27.2	>32.2	>19.8	>23.3
Normalized Pachymetric Difference Index (NPDI) (μm)	>5.4	>7.1	>3.9	>4.9

Higher-specificity cutoffs: CCT and MCT were calculated on the basis of the lower 2SD limit of corneal thickness. Difference and NPDI were calculated on the basis of the upper 2SD limit of the value. NPDI=[(CCT−MCT)/{(CCT+MCT)/2}] × 100.

Higher-sensitivity cutoffs: CCT and MCT were calculated on the basis of the lower 1SD limit of corneal thickness. Difference and NPDI were calculated on the basis of the upper 1SD limit of the value. NPDI=[(CCT−MCT)/{(CCT+MCT)/2}] × 100.