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Table 4 Corvis ST parameters of eyes by group

From: Comparisons of corneal biomechanical and tomographic parameters among thin normal cornea, forme fruste keratoconus, and mild keratoconus

Parameters TNC FFKC MKC Statistics P
A1T (ms) 7.205 ± 0.234 7.121 (6.748–7.801) 7.065 (6.692–7.867)# 9.168 0.010b
A1V (m/s) 0.153 (0.083–0.194) 0.163 (0.095–0.196)* 0.164 ± 0.022# 17.483 < 0.001b
A1DA (mm) 0.090 ± 0.007 0.097 (0.080–0.142)* 0.106 (0.080–0.152)#& 51.272 < 0.001b
A1L (mm) 2.176 ± 0.147 2.272 ± 0.096* 2.335 ± 1.223#& 32.121 < 0.001b
A2T (ms) 21.873 ± 0.382 22.015 ± 0.371* 22.016 (21.004–22.647)# 8.612 0.013b
A2V (m/s) − 0.285 ± 0.032 − 0.290 ± 0.039 − 0.305 ± 0.039# 3.984 0.021a
A2DA (mm) 0.096 (0.083–0.132) 0.107 (0.087–0.548)* 0.107 (0.086–0.138)# 27.666 < 0.001b
A2L (mm) 2.410 (1.525–4.009) 2.579 (1.589–4.510) 2.600 (11.850–4.462) 4.592 0.101b
HCT (ms) 16.812 ± 0.441 16.854 ± 0.588 16.969 (15.634–17.855) 3.237 0.198 b
HCDA (mm) 0.957 ± 0.096 1.001 ± 0.128 1.137 ± 0.124#& 10.759 < 0.001a
HCDL (mm) 6.556 ± 0.393 6.753 (5.250–7.459) 6.657 (5.505–7.323) 3.895 0.143 b
PD (mm) 5.174 (4.665–5.642) 5.247 (4.452–5.719) 5.229 (4.365–5.642) 6.244 0.044 b
HCR (mm) 6.544 ± 0.561 6.668 ± 0.581 6.3260 ± 0.745& 3.717 0.027 a
DA (mm) 1.083 ± 0.090 1.137 ± 0.124* 1.147 ± 0.095# 11.644 0.003 b
ARTh 369.149 (259.978–625.851) 424.172 ± 100.613 313.693 (171.693–641.209)#& 23.079 < 0.001b
DAR1 1.645 (1.572–1.793) 1.604 (1.507–1.770)* 1.630 ± 0.043 15.430 < 0.001b
DAR2 4.829 ± 0.340 4.863 ± 0.405 5.094 ± 0.541# 7.933 0.019 b
SP-A1 75.114 ± 11.054 73.638 (59.835–109.124) 69.976 (46.205–114.207) 6.846 0.033 b
CBI 0.915 (0.569–0.991) 0.742 (0.000–1.000)* 0.964 (0.000–1.000)& 22.490 < 0.001b
  1. TNC thin normal cornea; FFKC forme fruste keratoconus; MKC mild keratoconus; A1T time from starting until the first applanation; A1V velocity of the corneal apex during the first applanation; A1DA corneal deflection amplitude during the first applanation; A1L length at the first applanation; A2T time from starting until the second applanation; A2V velocity of the corneal apex during the second applanation; A2DA corneal deflection amplitude during the second applanation; A2L length at the second applanation; HCT time from the measurement beginning to the moment of reaching the highest concavity; HCDA corneal deflection amplitude at the moment of the highest corneal concavity; HCDL highest concavity deflection length; PD peak distance at the highest concavity; HCR central concave curvature at highest concavity; DA maximum deformation amplitude; ARTh ambrósio relational thickness to the horizontal profile; DAR1 the ratio between the deformation amplitude at the apex and at 1 mm from corneal apex; DAR2 the ratio between the deformation amplitude at the apex and at 2 mm from corneal apex; SP-A1 stiffness parameter at the first applanation; CBI corneal biomechanical index
  2. P is the value among the three groups. *, # and &represent statistically significant difference with TNC and FFKC, TNC and MKC, FFKC and MKC, respectively; arepresents one-way ANOVA, brepresents Kruskal-Wallis test