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

The lens is primarily responsible for focusing light onto the retina. It is a transparent, flexible structure located behind the iris and the pupil in the eye. The lens changes shape to adjust the focal distance, allowing the eye to focus on objects both near and far. This process is called accommodation. The ciliary muscles control the shape of the lens, enabling it to become more rounded for close objects or flatter for distant ones, thereby ensuring that light rays converge accurately on the retina, where they can be perceived as visual images.

While the cornea also plays a significant role in focusing light, it provides the majority of the eye's total optical power. However, the cornea's curvature is fixed, and it does not have the same ability to change shape in response to distance as the lens does. The retina is responsible for receiving and processing the light signals, but it does not focus light. The iris is involved in controlling the amount of light that enters the eye by adjusting the size of the pupil but does not have a role in focusing light.