Final answer:
The crystalline lens, located behind the iris, focuses light onto the retina and adjusts its shape for clear vision at different distances. With age, its flexibility decreases, leading to conditions like presbyopia that cause blurry near vision.
Step-by-step explanation:
The crystalline lens of the eye is a vital component for vision, located behind the iris and the pupil. Its primary function is to focus light onto the retina, specifically on the fovea centralis which has the highest density of light receptors and provides the sharpest vision. The lens is capable of changing shape thanks to the ciliary muscles, adjusting its focal length for clear vision of objects at varying distances, a process known as accommodation. Aging can lead to a loss of this flexibility, resulting in conditions such as presbyopia, where the lens can no longer focus on close objects, causing them to appear blurry. Myopia and hyperopia are other vision conditions affected by the shape and focusing ability of the lens.