Correlation between axial length and the elasticity of the posterior segment of eyeball in myopic eyes without posterior staphyloma: a shear wave elastography-based cross-sectional study

Abstract

Purpose: To investigate the correlation between axial length (AL) and the elasticity of the posterior segment wall of the eyeball using shear wave elastography in myopic eyes without posterior staphyloma.

Methods: This cross-sectional study enrolled 87 right eyes, including 29 with high myopia (spherical equivalent ≤ -6.00 D) and 58 with low myopia (-6.00 D < spherical equivalent ≤ -0.50 D). The AL measured with Pentacam and the elasticity of the eyeball wall at different locations (including the macular region, near the optic nerve, and near the midperiphery) could be reflected using shear wave elastography. Multivariate regression analysis was used to explore the correlations between AL and elasticity at different locations.

Results: A significantly lower elasticity measurement was observed in high myopia group at the macular region, 3.5 mm from the nasal side of the optic nerve, temporal and nasal sides of the optic nerve, and temporal and nasal sides of the midperiphery in both horizontal and vertical directions (P < 0.01). Furthermore, the elasticities at the macular region in both horizontal and vertical directions had significant correlations with AL (P < 0.001).

Conclusion: The elasticity of the eyewall at the macular area decreased with an increase in AL, which may explain why posterior scleral staphyloma is most likely to occur at the macular area. The macular area should be paid more attention in high myopia. These microstructural changes indicated by the difference in elasticity of the posterior segment wall maybe lead to the progression of posterior staphyloma.

Key messages: WHAT IS KNOWN : The local choroidal factors and a decreased biomechanical elasticity of the sclera have been regarded as important pathogenic factors of posterior staphyloma.

What is new: While posterior staphyloma had not yet occurred, the elasticity of the wall of the eyeball began to decrease. Shear wave elastography proved that the elasticity of the eye wall at the macular area decreased with an increase in axial length, which explain why posterior staphyloma is likely to occur at the macular area. The posterior scleral staphyloma is most likely to occur at the macular area, therefore the macular area should be paid more attention in highly myopic eyes.

Keywords: Axial length; Elasticity; Myopia; Shear wave elastography.