Table 2.

Characteristics of Bowman’s layer indices calculated on vertical topographic thickness maps of the layer in normal and keratoconus patients:

	Control	KC	P value	AUC	Sensitivity*	Specificity*	Cut-off*	Correlation to Avg-K	Correlation to Ast-K
BL total average thickness	15±1 μm	13±2 μm	0.056	0.78	60%	93%	13.3 μm	R=−0.48; P=0.007	R=−0.53; P=0.002
BL average thickness of the inferior half of the cornea	15±2 μm	12±3 μm	<0.001	0.87	80%	93%	13.5 μm	R=−0.62;P<0.001	R=−0.72; P<0.001
BL minimum thickness of the inferior half of the cornea	13±2 μm	7±3 μm	<0.001	0.96	93%	93%	11.5 μm	R=−0.59; P=0.001	R=−0.82; P<0.001
BEI	91±7	48±14	<0.001	1.00	100	100	80	R=−0. 60; P<0.001	R=−0.84; P<0.001
BEI-Max	75±8	40±13	<0.001	1	100	100	60	R=−0.59; P=0.001)	R=−0.82; P<0.001

-KC: keratoconus.

-AUC: area under the curve.

-BL: Bowman’s layer.

-BEI: Bowman’s ectasia index; defined as BL minimum thickness of the inferior half of the cornea divided by BL average thickness of the superior half of the cornea multiplied by 100.

-BEI-Max: defined as BL minimum thickness of the inferior half of the cornea divided by BL maximum thickness of the superior half of the cornea multiplied by 100.

-Avg-K: average keratometric readings.

-Ast-K: Keratometric astigmatism.

^*Chosen to maximize total diagnostic accuracy (minimize total number of errors).