OPTICAL AND STRUCTURAL DEVELOPMENT OF THE CRYSTALLINE LENS IN CHILDHOOD

PURPOSE. To document the development of key optical and structural par ameters of the crystalline lens throughout childhood and examine possi ble mechanisms by which lens power remains coordinated with the growth of the eye to maintain emmetropia. METHODS. Using cycloplegic autoref raction, video-based phakometry, and ultrasonography, the authors meas ured refractive error and crystalline lens parameters in 994 children in the first through eighth grades, who participated in the Orinda Lon gitudinal Study of Myopia, between one and five times from 1989 throug h 1993. Polynomial growth curves were fit to the data by maximum likel ihood estimation. The average annual rates of change in each parameter from each subject's longitudinal data were also estimated. RESULTS. T he lens radii of curvature flattened throughout childhood, jet decreas es in lens equivalent power stopped after 10 rears of age. This indica tes that the refractive index of the lens increased during later child hood. Lens thinning in early childhood also ceased after 10 years of a ge. The spherical volume of the lens showed no appreciable net increas e, but the axial length of the eye continued to grow throughout childh ood. The prevalence of myopia in our data increased sharply at age 10 years, reaching 21.3% by the age of 14 years. CONCLUSIONS. Concurrent thinning and flattening of the crystalline lens imply that the lens is mechanically stretched by the equatorial growth of the eye during chi ldhood. Changes in the patterns of lens development near the age of 10 years, concurrent with the onset of myopia, suggest that forces arise which interfere with equatorial growth, Such forces might diminish th e decreases in lens power and amplify axial elongation to promote myop ia.