LONGITUDINAL EVIDENCE OF CRYSTALLINE LENS THINNING IN CHILDREN

Purpose. Most earlier studies indicated that the eye's crystalline len s grows continually throughout life, but cross-sectional results of cr ystalline lens thinning during childhood have been reported. The autho rs investigated crystalline lens thickness in childhood using cross-se ctional and longitudinal data. Methods. The Orinda Longitudinal Study of Myopia is a community-based study of normal eye growth and myopia d evelopment in school-age children. During a 1- to 3-year period, A-sca n ultrasonographic lens thickness measurements of 869 children 6 throu gh 14 years of age were analyzed. Results. On average, between the age s of 6 and 10 years, the crystalline lens thins in its axial dimension by almost 0.2 mm. This thinning can be depicted by a cubic model. In this sample, the children with myopia had thinner crystalline lenses t han the children with emmetropia of the same age. Conclusions. This ar ticle provides the first longitudinal evidence that the crystalline le ns thins during the period of coordinated ocular growth between the ag es of 6 and 10 years. Further, it shows that lens thickness is associa ted with refractive error. Thinner crystalline lenses in children with myopia may result from one of two underlying mechanisms: Either the c rystalline lens exhausts its ability to compensate for axial elongatio n after undergoing accelerated lens thinning before the onset of myopi a, or the crystalline lens in the myopic eye may be thinner throughout childhood, during which it thins at a rate consistent with other refr active errors. If mechanical forces link eye growth to crystalline len s compensation, more complex, visually guided feedback loops may not b e needed to explain the normal eye growth that results in emmetropizat ion.