Abstract
Abstract: :
Purpose: We have created computer generated scale video animations of lens development, growth and ageing that highlight a number of key inter–species differences in lens anatomy. Methods: Lens structural parameters (anterior and posterior minor axis, equatorial major axis, fiber dimensions [width and thickness along length as well as length]).were derived from slit–lamp, light and transmission and scanning electron micrographs as well as cylindrical and azimuthal map projections of selected growth shells. This data was then used to create 2 and 3D computer assisted drawings (CADs) of lens structure at distinct periods of development, growth and ageing, and then animated in accelerated time frames. Results: While primary fiber formation is comparable in all vertebrate lenses, secondary fiber formation is somewhat different between species. As these fibers form, they simultaneously elongate bi–directionally and rotate about their long axis as they migrate posteriorly until their center point is equidistant from the poles. At that time the forming secondary fibers are fixed in place within the forming growth shell. Only their ends continue to elongate or grow until as a straight fiber they either define the origin of a suture branch or the termination of a suture branch, or as a fiber with opposite end curvature, they abut and overlap to form a suture branch. The anterior surface of all lenses has less curvature than the posterior surface. In addition, anterior suture branches are longer than posterior branches. Thus, fiber ends neither reach their respective anterior and posterior destinations at the same time nor one before the other. When fiber ends reach their respective anterior and posterior destinations is related to their equatorial position and suture type (line vs. Y vs. simple star vs. star vs. complex star). By extrapolation, fiber length and amount of end curvature varies as a direct function of suture type. Conclusions: The video animations reveal important inter–species structural differences that are known to quantifiably affect optical quality in both normal and pathological lenses. This information should be useful in planning future mechanistic studies to more specifically address the factors that produce key inter–species variations in lens anatomy known to affect its function and contribute to its malfunction.
Keywords: microscopy: electron microscopy • aging • anatomy