Corneal Biomechanical Properties in Myopic Eyes Measured by a Dynamic Scheimpflug Analyzer

Abstract

Purpose. To evaluate the corneal biomechanical parameters in myopic and emmetropic eyes using Corneal Visualization Scheimpflug Technology (CorVis ST). Methods. 103 myopic and emmetropic eyes of 103 patients were examined. Corneal biomechanical parameters, axial length, and mean keratometry were measured using CorVis ST, IOL Master, and topography, respectively. Corneal biomechanical properties were compared within four groups. Bivariate correlation analysis was used to assess the relationship between corneal biomechanical parameters and ocular characteristics. Results. Four of ten corneal biomechanical parameters, namely, deformation amplitude (DA), first- and second-applanation time (A1-time, A2-time), and radius at highest concavity (HC radius), were significantly different within the four groups (P < 0.05). In correlation analysis, DA was positively correlated with axial length (r = 0.20, P = 0.04); A2-time was positively correlated with spherical equivalent (SE) (r = 0.24, P = 0.02); HC radius was positively correlated with SE (r = 0.24, P = 0.02) and was negatively correlated with mean keratometry (r = −0.20, P = 0.046) and axial length (r = −0.21, P = 0.03). Conclusions. The corneal refraction-related biomechanical alterations were associated with ocular characteristics. Highly myopic eyes exhibited longer DA and smaller HC radius than do moderately myopic eyes; the eyes with longer axial length tend to have less corneal stiffness and are easier to deform under stress.

Corneal biomechanical properties in myopic eyes evaluated via Scheimpflug imaging

“…The severe and high myopia groups had a smaller A2-length than other groups. These findings are not in line with those from Wang et al [21], their study did not show the difference of A2-velocity between groups. Another study, consistent with our results, showed high myopia had greater A2-velocity compared to either low to moderate myopia or emmetropia using the Corvis ST. [20] A2-time, A2length and A2-velocity were significantly positively correlated with SE and negatively correlated with AL, this agreed with the ANOVA in the present study.…”

“…DA is the deformation amplitude at highest concavity and is regarded as a surrogate for corneal stiffness. [18,21,28] A higher DA value would represent a softer cornea due to a lower resistance to deformation. [28,29] Our findings showed that the higher the degree of myopia or the longer the axial length, the softer of the cornea is, which is consistent with previous studies.…”

“…[28,29] Our findings showed that the higher the degree of myopia or the longer the axial length, the softer of the cornea is, which is consistent with previous studies. [20,21,[30][31][32][33] But Miki et al [33] did not divide subjects into different groups according to SE or AL with relatively few participants. On the other hand, our research focus on corneal biomechanical properties in severe myopia in a large number of samples with rigorous screening criteria.…”

“…However, they did not take axial length (AL) into consideration. While Wang et al [21] suggested that there were significant differences between emmetropia, moderate myopia and high myopia in terms of deformation amplitude, first-and second-applanation time, and radius at highest concavity. However, Matalia et al [22] showed that cornea deformation parameters were unaffected by myopia.…”

Factors Associated With Corneal Deformation Responses Measured With a Dynamic Scheimpflug Analyzer

“…The ORA parameters are affected by various baseline factors such as refraction, 8,9 axial length, [21][22][23][24] age, 23 IOP, 23 corneal curvature, 23 and central corneal thickness (CCT). 25 Parameters measured with the Corvis ST are associated with the axial length, 26 age, 27,28 diabetes, 29 IOP, 13,25,[30][31][32] corneal curvature, 26,33 and CCT. 34 To clarify the association between ocular disorders and corneal biomechanics, it is essential to adjust for the possible confounding effects of factors that potentially affect corneal biomechanical parameters.…”