Figure 1.

Lens biology and cataract formation. A) The lens is located behind the cornea and in front of the retina.¹⁸ B) (1) The lens of the eye is enclosed by the lens capsule. (2) The anterior surface of the lens (top) consists of a single layer of epithelial cells. Cuboidal epithelial cells near the equator proliferate throughout life and elongate (3) anteriorly and posteriorly until their ends reach the two lens poles (top and bottom). At this stage, the hexagonal fiber cells degrade their organelles (4, 6). The nuclei are indicated as black dots. Thus, the lens consists primarily of long fiber cells devoid of cytoplasmic organelles (5). The core of the lens (lens nucleus) is composed of the primary fiber cells (7). [Reproduced from Perng et al.²⁰ with permission from Elsevier.] C) Schematics illustrating the locations of cortical, nuclear, and posterior subcapsular opacities. In cortical cataract, opaque streaks are observed in the cortex, circumscribing the lens, while in nuclear cataract, the opacity is in the center on the lens. Posterior subcapsular cataract describes an opacity at the back of the lens that have dot opacities in the cortex as well.