The crystalline lens is the most important structure in the optical system. It is already created during the first months of pregnancy and continuously builds new lens fibres that are densely packed in concentric layers (appositional growth) throughout life. The refractive power of the crystalline lens is roughly one-third of the eye’s total power. The crystalline lens allows the formation of sharp retinal images of near and distant objects alike. This is achieved by contracting (bulging) or relaxing the lens. The crystalline lens also absorbs harmful radiation, especially UV-A rays are totally absorbed, to protect the light-sensitive retina.