Which structure focuses light before it reaches the retina?

The lens plays a crucial role in the visual process by focusing light onto the retina. It is a transparent, flexible structure located behind the iris and pupil. The lens adjusts its shape through the action of the ciliary muscles to focus on objects at varying distances—a process known as accommodation. When light enters the eye, it is first refracted by the cornea, but the lens fine-tunes that focus to ensure that light rays converge correctly on the retina, where the photoreceptive cells convert the light into neural signals for processing.

The cornea also contributes to focusing light but does so in a fixed manner, primarily responsible for the majority of light refraction entering the eye. The sclera is the protective outer layer of the eye and does not play a role in focusing light. The retina is where the light is projected, but it does not have a role in focusing it; instead, it's responsible for detecting the light and sending signals to the brain. This sequential processing is essential for clear vision, highlighting the specific role of the lens in the overall mechanism.