The structural basis of the crystalline lens sulcus

Purpose. To demonstrate by correlative light (LM), transmission (TEM), scanning electron microscopy (SEM) and computer generated three-dimensional (3D) reconstructions, that the crystalline lens sulcus, like the zones of discontinuity, both observed by Scheimpflug slit-lamp microscopy, result from structurally distinct fiber order and packing along the visual axis. Methods. The radial cell column organization of normal adult human lenses (n = 12; age range 20 - 88) was analyzed in thick and thin sections taken along both the equatorial and visual axes by LM and TEM. Fiber cell curvature from anterior to posterior sutures was ascertained by SEM. Fiducial information from these studies (lens axial dimensions, fiber length, width and degree of curvature) was used to produce accurate computer generated 3D reconstructions. Results. The lens sulcus consists of the middle or equatorial segment of all fibers. These segments lack curvature and thus, are all oriented essentially parallel to the visual axis. In contrast, as has been shown previously, the anterior and posterior zones of discontinuity are the result of the anterior and posterior segments of the same fibers arranged in progressively more complex sutures (Koretz, Cook & Kuszak, Vis. Res. 34(22):2955-62, 1994). The crescent and end curvatures of these segments result in a change in the orientation of fibers to the visual axis from parallel in the central sulcus, to perpendicular in the zones of discontinuity. Conclusion. The central lens sulcus and zones of discontinuity are a function of structurally distinct fiber segments aligned at variable orientation to the visual axis in human lenses.

Duke Scholars

Author Martin Joseph Costello III Ophthalmology