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

The part of the eye that is primarily responsible for focusing light on the retina is the lens. The lens acts as a flexible structure that can change shape to focus light precisely onto the retina for clear vision. Its ability to adjust shape through the action of ciliary muscles allows for accommodation, enabling the eye to focus on objects at various distances.

While the cornea does contribute significantly to the eye's focusing ability, it primarily does so by refracting light. It provides the initial focus rather than the fine-tuning that the lens accomplishes. The iris regulates the amount of light entering the eye by controlling the size of the pupil but does not focus light itself. The pupil serves as an opening for light to enter the eye but does not play a role in focusing. Understanding the specific roles of these components highlights the importance of the lens in visual acuity and clarity.