Evaluation of corneal biomechanical parameters and related influencing factors in myopic patients by Corvis ST

Abstract

AIM: To assess the differences in corneal biomechanical parameters and their correlation with other ocular biometric parameters in myopic patients using a corneal visualisation scheimpflug technology(Corvis ST).METHODS: A total of 132 myopic patients who received treatment in the department of refractive surgery of Eyegood Ophthalmic Hospital from May to December 2021 were selected, and the data of right eye were taken. The subjects were classified into low and moderate myopia(-0.50 to -6.00D), high myopia(>-6.00D to <-8.00D), and super high myopia(≥-8.00D)according to the spherical equivalent(SE). The basic parameters of corneal biomechanical deformation measured with Corvis ST included the amount of corneal displacement at highest degree of concavity(DA), radius of curvature at highest concavity(HCR), and distance between the two peaks of the cornea at highest concavity(PD); stiffness parameters at applanation 1(SP-A1), integrated radius(IR), deformation amplitude ratio(DA ratio), Ambrosio relational thickness horizontal(ARTh), Corvis biomechanical index(CBI). Other ocular biometric parameters measured included SE, intraocular pressure(IOP), axial length(AL), central corneal thickness(CCT), white-to-white(WTW)and retinal nerve fiber layer(RNFL)thickness. The differences in corneal biomechanical parameters were compared among the three groups of myopic patients, and the correlation between corneal biomechanical parameters and other ocular biometric parameters and age was further analyzed.RESULTS: The SP-A1 in the low and moderate, high, and super high myopia groups were 106.8±16.2, 115.6±21.9, and 106.9±11.5, respectively. The SP-A1 in the high myopia group was higher than that in the low and moderate and severe myopia groups(all P<0.05). All corneal biomechanics were significantly correlated with CCT(P<0.01); all corneal biomechanics were correlated with IOP except ARTh(P<0.05); AL was significantly and positively correlated with PD(r=0.270, P=0.002), weakly and positively correlated with HCR(r=0.177, P=0.043), and weakly and negatively correlated with IR(r=-0.183, P=0.036); WTW was positively correlated with PD, DA and DA ratio(r=0.363, P<0.001; r=0.252, P=0.003; r=0.200, P=0.02); there was no correlation between corneal biomechanical parameters and age, SE, and RNFL.CONCLUSION: Corneal stiffness was higher in high myopia patients than in patients with low to moderate and super high myopia. IOP and CCT were both important factors affecting corneal biomechanics. Some of the biomechanical parameters also have certain correlation with AL and WTW. As the growth of axial length, the PD of corneal deformation and HCR were larger, and IR was smaller, but HCR and IR had little significance; the longer the WTW, the greater the corneal deformation amplitude. In clinical practice, attention should be paid to the corneal biomechanical parameters in patients with super high myopia.

Keywords

• corneal biomechanics
• myopia
• axial length
• corneal visualisation scheimpflug technology(corvis st)