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Relationship between changes in crystalline lens shape and axial elongation in young children.

PURPOSE
To evaluate the relationship between changes in crystalline lens shape and axial elongation during growth in young children.


METHODS
Twenty-five patients (age: 1 month to 6 years) who underwent head magnetic resonance imaging (MRI) were included in the analysis. Refractive error was measured with an autorefractor in 22 patients. Crystalline lens dimensions and axial length (AL) were obtained from the MR images. The radius of curvature and asphericity of the crystalline lens were measured using reconstructed MR images. Crystalline lens shape and eyeball shape were numerically expressed by elliptic Fourier descriptors (EFDs) on the basis of MR images. The contours of the crystalline lens and eyeball were evaluated by principal component analysis of the EFDs.


RESULTS
The average anterior and posterior radii of curvature were 6.21 mm (range across ages from 3.89-7.26 mm) and -4.81 mm (range across ages from -2.93 to -5.67 mm). These were closely correlated with age by logarithmic analysis. The first principal component (PC1) of the crystalline lens explained 89.15% of the total variance in lens shape, and it was also significantly correlated with age (Pearson's r = 0.648, P < 0.001) and AL (r = 0.847, P < 0.001). In the multiple linear regression analysis in which AL was a dependent variable, only the PC1 of the crystalline lens was associated with AL.


CONCLUSIONS
Axial elongation is related to the entire contour of the crystalline lens. This result shows that axial elongation progresses in parallel to change in the crystalline lens shape.