Biomechanical properties of the myopic choroid

Retina-derived growth signals relayed from the choroid to the sclera cause remodeling of the extracellular matrix, resulting in myopic ocular elongation. However, no studies have assessed changes in choroidal biomechanical properties during myopia progression. The present study utilized 7-μm-resolution scanning acoustic microscopy (SAM) to assess biomechanical properties of choroids in guinea pig eyes with form-deprivation (FD) induced myopia. Specifically, neonatal guinea pigs underwent unilateral FD for 1 week (resulting in moderate to high myopia). 12-μm-thick serial cryosections of eyes were scanned with SAM and two-dimensional maps of bulk modulus (K), mass density (rho) were calculated. We found that the choroid had considerable intrinsic strength arising from its biomechanical properties and these were differentially affected by myopia in central and peripheral regions. Choroidal biomechanical values were also highly correlated with those in adjacent scleral regions, and the choroidal-scleral association was stronger in myopic eyes. In conclusion, biomechanical changes observed in the choroid of myopic eyes were mirrored to those observed in the adjacent sclera. These new findings suggest that the choroid remodeling may accompany myopia and opens the door to the source of the signals that cause scleral remodeling in myopia.