What is the structure responsible for most of the refractive work of the eye?

The cornea is the structure that is responsible for most of the refractive work of the eye, significantly bending (or refracting) light rays as they enter the eye. The cornea's curvature and its transparent nature allow it to play a critical role in focusing light onto the retina, where images are formed.

While the lens also contributes to the eye's ability to focus light, particularly during the accommodation process (adjusting focus for near and far objects), the majority of refraction occurs at the cornea due to its fixed curvature. The iris, which is responsible for regulating the amount of light that enters the eye by adjusting the size of the pupil, does not play a direct role in light refraction. The retina's primary function is to convert light into neural signals for the brain to process, but it is not involved in the process of bending light. Therefore, the cornea is the primary refractive element in the eye, making it crucial for proper vision.