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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