One-third of the refraction of light that enters the eye is controlled by which part?

The lens is responsible for a significant portion of the refraction of light entering the eye, primarily adjusting the focus of light onto the retina. It fine-tunes the focus of light rays after they have passed through the cornea, which is the main refractive surface of the eye. The lens can change its shape, becoming thicker or thinner, which allows it to focus on objects at various distances, a process known as accommodation. While the cornea contributes the majority of the eye's overall refractive power, the lens is crucial for making precise adjustments. This ability to refract light and alter focus is essential for clear vision.