FIGURE 2.

Lens accommodation and anatomy. (A) The lens changes shape to fine focus light coming from sources at various distances onto the retina. When viewing objects that are far away, the lens is unaccommodated and relatively flat (left). During accommodation, the lens becomes more spherical to focus near objects (right). Adapted from an open-source Pearson Scott Foster illustration (not drawn to scale). (B) An illustration (not drawn to scale) depicting a longitudinal (anterior-posterior) section of the lens with a monolayer of epithelial cells on the anterior hemisphere (colored cells) and a bulk mass of elongated lens fibers (white cells). Lens fibers extend from the anterior to posterior poles. The lens capsule, a thin basement membrane, encapsulates the entire tissue. Anterior epithelial cells (blue) are cobblestone in shape and quiescent. These cells normally do not proliferate. Equatorial epithelial cells (orange) in the germinative zone proliferate, migrate and differentiate into new layers of lens fibers. During migration and differentiation, equatorial epithelial cells transform from randomly organized cells (orange) into highly organized hexagonal cells arranged into neat rows (green). Lifelong lens growth depends on the addition of new fiber cells in concentric shells at the periphery of the lens. Lens fibers retain the organized hexagonal rows as seen in the cross-section view. Newly formed fibers elongate toward the anterior and posterior poles, migrating along the apical surface of epithelial cells or the posterior capsule, respectively. Fully elongated fibers at the anterior and posterior poles will detach from the epithelial cells or lens capsule and contact the elongating fiber from the opposing sides forming the Y-suture. Fiber cell maturation eliminates light-scattering cell organelles in the inner fiber cells, and the lens nucleus, or the central core of the tissue, is composed of tightly compacted fiber cells in the middle of the lens (purple). Modified from (Cheng et al., 2019).