The main purpose of the crystalline lens in the eye is to focus light onto the retina for clear vision. The lens adjusts its shape through the action of ciliary muscles, allowing the eye to focus on objects at different distances, a process called accommodation. When light rays enter the eye, the lens refracts them to converge precisely at the retina, where photoreceptor cells convert light into neural signals. Proper functionality of the crystalline lens is vital for maintaining sharp vision, and its opaqueness can lead to conditions such as cataracts.