Abstract
Purpose :
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 mechanical properties during myopia progression. The present study utilized 7-µm-resolution scanning acoustic microscopy (SAM) to assess the mechanical properties of choroids in guinea pig eyes with form-deprivation (FD) induced myopia.
Methods :
Eleven 1-week-old guinea pigs underwent unilateral FD for 1 week (resulting in -3 to -9.3D myopia). Eyes were enucleated, flash-frozen and 12-μm-thick serial cryosections were obtained in either a vertical (superior/inferior) or horizontal (nasal/temporal) orientation across the posterior pole. Specimens were scanned with SAM and two-dimensional maps of bulk modulus (K), mass density (rho) and choroidal thickness were calculated from values averaged across each sample region (approximately every 200 µm). Paired t-tests were performed to determine statistical differences between the: FDM versus fellow-control eyes, choroid versus sclera tissue, and proximal versus distal regions. Univariate regression analysis was performed to assess the association between choroidal biomechanical parameters (K or rho) and 1) choroidal thickness, 2) the level of induced myopia, and 3) corresponding scleral biomechanical parameters.
Results :
In untreated eyes, K was significantly larger and rho was significantly lower in proximal compared to distal regions (p=0.016, p<0.001 respectively). In contrast, in myopic eyes, differences in rho between proximal and distal sections did not reach statistical significance (p = 0.379). Choroidal and scleral K were not correlated in control eyes, except in the SUP-proximal region (R=0.36, p=0.016). In contrast, after 1 week of FDM, choroidal and scleral K became locally correlated (R=0.45, p<0.001) showing that local stiffness was similar between adjacent choroidal and scleral samples. Choroidal and scleral rho showed significant positive correlations in both control and FDM eyes.
Conclusions :
Biomechanical changes observed in the choroid of myopic eyes were mirrored in the adjacent sclera. These new findings suggest that choroidal remodeling may accompany myopia and reveal the source of the signals that cause scleral remodeling in myopia.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.