Corneal Biomechanical Assessment Using Corneal Visualization Scheimpflug Technology in Keratoconic and Normal Eyes

Table 1

Comparison of tomography and biomechanical parameters between the KC and control group, mean ± SD (range).

	Control	KC	P value
Tomography
Flat keratometry (diopters)	43.27 ± 1.56 (38.5–48.8)	48.47 ± 5.94 (40.1–69.3)	0^a
Steep keratometry (diopters)	44.39 ± 1.61 (39.2–49.5)	52.09 ± 6.82 (40.8–72.9)	0^a
Mean keratometry (diopters)	43.82 ± 1.54 (38.9–48.8)	50.18 ± 6.19 (40.8–71)	0^a
Astigmatism (diopters)	1.12 ± 0.68 (0–3.7)	3.63 ± 2.72 (0.1–9.3)	0^a
Central corneal thickness (μm)	546.1 ± 30.09 (498–629)	456.37 ± 57.45 (302–557)	0^a
Corneal volume at 3.0 mm (mm^3)	3.94 ± 0.22 (3.6–4.6)	3.45 ± 0.33 (2.7–4.1)	0^a
Corneal volume at 5.0 mm (mm^3)	11.56 ± 0.64 (10.5–13.3)	10.57 ± 0.76 (9–12.4)	0^b
Corneal volume at 7.0 mm (mm^3)	24.89 ± 1.4 (22.7–28.7)	23.31 ± 1.54 (20.3–27)	0^b
Corneal volume at 10 mm (mm^3)	61.2 ± 3.67 (55.8–70.9)	58.18 ± 4.01 (50.6–68.3)	0^b
Anterior chamber angle (degree)	39.14 ± 5.78 (28.4–63.6)	37.25 ± 5.71 (23.6–52.5)	0.074^b
Anterior chamber depth (mm)	3.17 ± 0.32 (2.2–4.03)	3.43 ± 0.4 (2.16–4.39)	0^b
Anterior chamber volume (mm^3)	185.2 ± 36.73 (92–276)	203.18 ± 35.64 (124–263)	0.007^b
Biomechanics
A-time1 (ms)^c	7.52 ± 0.43 (6.81–8.58)	7.04 ± 0.36 (5.91–7.74)	0^b
A-length1 (mm)^d	1.78 ± 0.27 (1.34–2.28)	1.69 ± 0.33 (0.98–2.35)	0.108^b
𝑉in (m/s)^e	0.15 ± 0.03 (0.08–0.24)	0.17 ± 0.04 (0.11–0.26)	0.026^a
A-time2 (ms)^c	22.18 ± 0.52 (21.27–23.3)	22.5 ± 0.55 (21.46–23.69)	0.001^b
A-length2 (mm)^d	1.9 ± 0.49 (1.01–2.86)	1.47 ± 0.46 (0.66–2.54)	0^b
𝑉out (m/s)^e	–0.39 ± 0.08 (–0.6 to 0.23)	–0.53 ± 0.15 (–0.88 to 0.24)	0^a
Highest concavity time (ms)^f	16.72 ± 0.49 (15.25–18.25)	16.67 ± 0.94 (11.32–17.79)	0.419^a
Highest concavity curvature (mm)^g	7.52 ± 1.05 (4.1–10.75)	5.59 ± 2.32 (2.75–16.83)	0^b
Peak distance (mm)^h	4.50 ± 1.43 (2.21–5.99)	4.50 ± 1.43 (2.15–6.29)	0.585^a
Deformation amplitude (mm)^i	1.08 ± 0.11 (0.87–1.33)	1.32 ± 0.19 (0.92–1.96)	0^b
IOP-GAT (mmHg)^j	14.85 ± 2.79 (9.5–21)	12.09 ± 1.92 (7.5–15.5)	0^b

 ^aWilcoxon rank-sum test; ^bindependent two-sample t-test; ^cA-time₁ and A-time₂: time from the start until the first applanation and second applanation, respectively; ^dA-length₁ and A-length₂: length of the flattened cornea at the first applanation and second applanation; ^e𝑉_in and 𝑉_out: corneal velocities during the first and second applanation moments; ^f time from the start until the highest concavity of the cornea was reached; ^gcurvature radius of the highest concavity; ^hdistance of the two “knees” at the highest concavity; ⁱmaximum deformation amplitude at the corneal apex, from start to the highest concavity; ^jintraocular pressure measured by Goldmann applanation tonometry.