The Mammalian Ocular Lens in Focus: Development, Anatomy, Physiology, Transparency, Biomechanics, and Age-related Challenges.

The lens is a transparent, ellipsoid organ in the anterior chamber of the eye that focuses light onto the retina. Composed of epithelial cells and fiber cells, this 3-dimensional tissue is highly organized to ensure a clear light path and utilizes multiple strategies to establish and maintain a high refractive index and transparency. In humans, the lens undergoes shape changes to focus light from different distances in a process known as accommodation, and these elastic and biomechanical properties of the lens rely on tissue, cellular, and molecular mechanisms. Cataracts, defined as any opacity in the normally transparent lens, remain the leading cause of blindness in the world. Presbyopia, due to age-related changes in lens stiffness, has been linked to accommodative decline and the need for reading glasses. This review will explore mammalian lens development and lifelong growth, crystallins and cytoskeletal proteins, cell-cell communication and microcirculation, lens biomechanics, and the challenges and novel methods for studying this unique tissue.