Revisiting corneal topography for the diagnosis of keratoconus: use of Rabinowitz’s KISA% index

Figures & data

Table 1 Topographic index values

	Patients	Control	P value
K value	54.68 ± 8.78	46.48 ± 1.78	<0.01
I-S value	5.62 ± 7.04	1.91 ± 1.12	<0.001
AST	4.92 ± 2.81	4.26 ± 2.41	0.209
SRAX	13.88 ± 18.68	5.32 ± 6.41	0.003
KISA%	10126.67 ± 13662.47	21.35 ± 16.63	<0.01

Abbreviations: K, keratometry; I-S, inferior-superior; AST, keratometric astigmatism; SRAX, relative skewing of the steepest radial axes; KISA%, keratoconus percentage index.

Figure 1 Corneal topography images of patient 1 (A) right eye and (B) left eye and patient 2 (C) right eye and (D) left eye.

Table 2 Measured parameters of topographic indices

Variable	Sensitivity (%)	Specificity (%)	Positive predictive value (%)	Negative predictive value (%)
K value	82	68	71.93	79.09
I-S value	74	38	54.41	59.38
AST	88	10	49.44	45.45
SRAX	24	96	85.71	55.81
KISA%	96	100	100	96.15

Abbreviations: K, keratometry; I-S, inferior-superior; AST, keratometric astigmatism; SRAX, relative skewing of the steepest radial axes; KISA%, keratoconus percentage index.