Which part of the eye is primarily responsible for focusing light?

The lens of the eye plays a crucial role in focusing light onto the retina, which is essential for clear vision. It is a flexible, transparent structure located behind the iris that changes shape, allowing it to adjust the focal distance. When light enters the eye, it first passes through the cornea, which provides some initial focusing power; however, it is the lens that fine-tunes the focus for objects at varying distances. The ability of the lens to change its curvature is known as accommodation, enabling clear vision for both near and distant objects.

In contrast, while the cornea contributes to the eye’s overall focusing capacity, most of the fine adjustment comes from the lens. The iris regulates the amount of light entering the eye but does not focus light itself, and the retina is where the focused image is received and converted into neural signals for the brain to interpret. Thus, focusing light onto the retina primarily falls within the lens's functional responsibilities.