Characteristics of Corneal Biomechanics in Chinese Preschool Children With Different Refractive Status

Abstract

Purpose: To investigate the characteristics of corneal biomechanics in Chinese preschool children with different refractive status. Methods: Study participants were 108 Chinese children (216 eyes) aged 4 to 6 years with a spherical equivalent refraction between −9.00 and +9.00 diopters (D). Cycloplegic refraction was measured using an autorefractor, axial length using an IOL Master (Zeiss, Oberkochen, Germany), and corneal biomechanical metrics and corneal power using an ultra-high-speed camera (Corvis ST; Oculus, Wetzlar, Germany) and Pentacam (Oculus; Menlo Park, CA). Differences in corneal biometry and biomechanical characteristics among myopia, emmetropia, and hyperopia eyes were analyzed by SPSS 17.0. Results: The spherical equivalent refraction was significantly positively correlated with the stiffness parameter at the first applanation (SP-A1, r = 0.22, P < 0.01) and corneal velocity at the second applanation (A2 velocity, r = 0.25, P < 0.001), whereas it was negatively correlated with the peak distance (r = −0.32, P < 0.001) and deformation amplitude ratio (DA ratio, r = −0.34, P < 0.001). In the hyperopia, emmetropia, and myopia groups, the SP-A1 successively decreased (108.70 ± 22.93 vs. 100.50 ± 18.98 vs. 97.97 ± 18.91, P < 0.01), whereas the peak distance progressively increased (4.39 ± 0.32 vs. 4.56 ± 0.30 vs. 4.63 ± 0.34 mm, P < 0.001). In the same order of groups, an increasing trend was found for the axial length (21.11 ± 0.76 vs. 22.39 ± 0.72 vs. 24.09 ± 1.37 mm, P < 0.001), central anterior chamber depth (CACD, 3.04 ± 0.41 vs. 3.21 ± 0.33 vs. 3.37 ± 0.40 mm, P < 0.001) and flat meridian keratometry (K1, 41.92 ± 1.59 vs. 42.73 ± 1.39 vs. 42.98 ± 1.60 D, P < 0.001). Central corneal thickness significantly decreased in the same order of groups (565.46 ± 33.22 vs. 551.97 ± 24.66 vs. 543.36 ± 37.74 µm, P < 0.001). Conclusions: Corneal stiffness is reduced in myopia and increased in hyperopia compared with emmetropia in children aged 4 to 6 years. Corneal biometry and biomechanical characteristics in preschool children seem to depend on refractive status.

Age distribution and associated factors of cornea biomechanical parameter stress-strain index in Chinese healthy population

“…Especially the cornea in high myopia had faster outward corneal velocity (OCV) and higher CDA compared to emmetropia [ 16 ]. Long found in Chinese children, SP - A1 declined gradually between presbyopia, emmetropia and myopia groups [ 38 ]. However, in Lim’s study, CH and CRF were not significantly correlated with refractive errors by ORA measurement in corneal biomechanics in children aged 7–9 years.…”

Corneal biomechanical properties in myopic eyes evaluated via Scheimpflug imaging

“…The higher the degree or the longer the AL of the myopic eye, the less time is needed to return to the origin after applanation, as its viscoelasticity increased. In a recent study [ 27 ], myopia had greater A2-velocity indicating that the cornea tends to be more deformable and softer than emmetropia and hyperopia in children. Therefore, A2-velocity may be another indicator of corneal elasticity, as Lee et al [ 12 ], Miki et al [ 24 ] and Wang et al [ 28 ] suggested.…”

Age Distribution and Associated Factors of Cornea Biochemical Parameter Stress-Strain Index in Chinese Healthy Population

“…Especially the cornea in high myopia had worse biomechanics compared to emmetropia 15 . Long found in Chinese children, SP -A1 declined gradually between presbyopia, emmetropia and myopia group 33 . However, in Lim's study, CH and CRF were not signi cantly correlated with refractive errors by ORA measurement in corneal biomechanics in children aged 7-9 years.…”