A Critical Assessment of Friedenwald’s Technique for Estimating the Coefficient of Rigidity of the Cornea

Table 1

Distribution of Ko estimations according to results taken by the two operators from keratoconus, post-CXL, and normal controls. The number of Ko values (proportion of total in parenthesis) per Ko range. K-S = Result of Kolmogorov–Smirnov test for normality of data in each column. Indicates where the significance of the K-S statistic was <0.05 after excluding Ko values ≥ 0.11.

	Operator 1			Operator 2
Ko range (mmHg/μL)	Keratoconus	Post-CXL	Normal	Keratoconus	Post-CXL	Normal
0–0.01	9 (0.18)	7 (0.18)	1 (0.05)	6 (0.12)	9 (0.23)	1 (0.05)
0.011–0.02	21 (0.41)	15 (0.38)	9 (0.45)	24 (0.47)	20 (0.50)	10 (0.50)
0.021–0.03	14 (0.28)	11 (0.28)	2 (0.10)	11 (0.22)	5 (0.25)	5 (0.25)
0.031–0.04	5 (0.10)	4 (0.10)	4 (0.20)	2 (0.04)	1 (0.025)	1 (0.05)
0.041–0.05			1 (0.10)	2 (0.04)	2 (0.05)	1 (0.05)
0.051–0.06				1 (0.02)
0.061–0.07
0.071–0.08
0.081–0.09				1 (0.02)
0.091–0.10
≥0.11	2 (0.04)	3 (0.08)	3 (0.15)	4 (0.08)	3 (0.075)	2 (0.10)
K-S	0.262	0.348	0.199	0.340	0.289	0.387