Correlation between corneal biomechanics and Schlemm canal and trabecular meshwork morphology in myopia

Objective  To evaluate the correlation between corneal biomechanical parameters and Schlemm canal (SC) and trabecular meshwork (TM) in patients with myopia.

Methods  Eighty-one consecutive patients who underwent refractive surgery at Wuhan EyeGood Ophthalmology Hospital from May to December 2021 were enrolled.Patients were divided into two groups according to spherical equivalent (SE) and axial length (AL), including 39 patients with 39 eyes in low to moderate myopia group (SE: -0.5 to -6.0 D, AL<26 mm) and 42 patients with 42 eyes in high myopia group (SE≤-6.0 D, AL≥26 mm).Another 20 cases (20 eyes) from the same period of health examinations were included as a healthy control group, with 10 males and 10 females.All subjects’ right eye data were included for analysis.The corneal biomechanical parameters were measured with Corvis ST.The morphology of the SC and TM was observed with Zeiss Cirrus HD-OCT 5000.The differences in corneal biomechanical parameters, nasal SC (SC-N) area, temporal SC (SC-T) area, nasal TM (TM-N) width and thickness and temporal TM (TM-T) width were compared between the two groups.Correlations between corneal biomechanical parameters and SC, TM and biomechanically corrected intraocular pressure (bIOP) in myopic patients were analyzed using Pearson linear correlation analysis.The study followed the Declaration of Helsinki, and the study protocol was reviewed and approved by the Ethics Committee of Wuhan EyeGood Ophthalmology Hospital (No.AGQGSS-06).All patients were aware of the purpose and significance of this study and voluntarily signed the informed consent form.

Results  The distance between the two peaks of the cornea at highest concavity (PD) was (5.49±0.28)mm in high myopia group, which was higher than (5.36±0.28)mm in low to moderate myopia and (5.05±0.29)mm in healthy control group, and the radius of curvature at highest concavity (HCR) and the stress-strain index (SSI) values in high myopia group were lower than those in low to moderate myopia and healthy control groups, with statistically significant differences (all P<0.05).The SC-T area and SC-N area were significantly higher and TM-T thickness was lower in high myopia group than those in low to moderate myopia and healthy control groups (all P<0.05).PD was positively correlated with SC-N area in myopic patients ( r=0.26, P=0.02).bIOP was negatively correlated with PD, the amount of corneal displacement at highest degree of concavity (DA), inverse concave radius (IR) and deformation amplitude ratio (DA ratio) ( r=-0.79, -0.81, -0.45, -0.50; all P=0.00) and positively correlated with stiffness parameters at applanation 1 (SP-A1) and SSI ( r=0.45, 0.46; all P=0.00).

Conclusions  PD values are greater in myopic patients.The greater the PD, the greater the SC-N area.The greater the refractive error, the longer the AL, and the thinner the TM thickness.

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