Purpose. To assess and
compare changes in the biomechanical properties of the cornea following
different corneal collagen cross-linking protocols using scanning acoustic
microscopy (SAM).
Methods. Ten donor human corneal pairs were divided
into two groups consisting of five corneal pairs in each group. In group A,
five corneas were treated with low-fluence (370 nm, 3 mW/cm2)
cross-linking (CXL) for 30 minutes. In group B, five corneas were treated with
high-fluence (370 nm, 9 mW/cm2) CXL for 10 minutes. The
contralateral control corneas in both groups had similar treatment but without
ultraviolet A. The biomechanical properties of all corneas were tested using
SAM.
Results.
In group A, the mean speed of sound in the treated corneas was 1677.38 ± 10.70
ms−1 anteriorly and 1603.90 ± 9.82 ms−1 posteriorly,
while it was 1595.23 ± 9.66 ms−1 anteriorly and 1577.13 ± 8.16 ms−1
posteriorly in the control corneas. In group B, the mean speed of sound of the
treated corneas was 1665.06 ± 9.54 ms−1 anteriorly and 1589.89 ±
9.73 ms−1 posteriorly, while it was 1583.55 ± 8.22 ms−1
anteriorly and 1565.46 ± 8.13 ms−1 posteriorly in the untreated
control corneas. The increase in stiffness between the cross-linked and control
corneas in both groups was by a factor of 1.051×.
Conclusions. SAM
successfully detected changes in the corneal stiffness after application of
collagen cross-linking. A higher speed-of-sound value was found in the treated
corneas when compared with the controls. No significant difference was found in
corneal stiffness between the corneas cross-linked with low- and high-intensity
protocols.
Purpose. To explore the
biomechanical changes induced by repeated cross-linking using scanning acoustic
microscopy (SAM).
Methods. Thirty human corneas
were divided into three groups. In group A, five corneas were cross-linked once.
In group B, five corneas were cross-linked twice, 24 hours apart. In group C,
five corneas were cross-linked three times, 24 hours apart. The contralateral
controls in all groups had similar treatment but without UV-A. The speed of
sound, which is directly proportional to the square root of the tissue's
elastic modulus, was assessed using SAM.
Results. In group A, the speed
of sound of the treated corneas was 1677.38 ± 10.70 ms−1 anteriorly
and 1603.90 ± 9.82 ms−1 posteriorly, while it was 1595.23 ± 9.66 ms−1
anteriorly and 1577.13 ± 8.16 ms−1 posteriorly in the controls. In
group B, the speed of sound of the treated corneas was 1746.33 ± 23.37 ms−1
anteriorly and 1631.60 ± 18.92 ms−1 posteriorly, while it was
1637.57 ± 22.15 ms−1 anteriorly and 1612.30 ± 22.23 ms−1
posteriorly in the controls. In group C, the speed of sound of the treated
corneas was 1717.97 ± 18.92 ms−1 anteriorly and 1616.62 ± 17.58 ms−1
posteriorly, while it was 1628.69 ± 9.37 ms−1 anteriorly and 1597.68
± 11.97 ms−1 posteriorly in the controls. The speed of sound in the
anterior (200 × 200 μm) region between the cross-linked and control corneas in
groups A, B, and C was increased by a factor of 1.051 (P = 0.005), 1.066 (P = 0.010), and 1.055 (P = 0.005) respectively. However, there was no
significant difference among the cross-linked corneas in all groups (P = 0.067).
Conclusions. A significant
increase in speed of sound was found in all treated groups compared with the
control group; however, the difference among the treated groups is not
significant, suggesting no further cross-links are induced when collagen
cross-linking treatment is repeated.