Which structure in the eye is primarily responsible for light refraction?

The structure primarily responsible for light refraction in the eye is the cornea. The cornea is the transparent front layer of the eye and provides most of the eye's total refractive power. It bends (refracts) incoming light rays as they enter the eye, helping to focus them onto the retina, which is the light-sensitive layer at the back of the eye.

Although the lens also plays a role in refraction by fine-tuning the focus of the light on the retina, it primarily adjusts the focal distance via accommodation. In contrast, the iris controls the amount of light entering the eye by adjusting the size of the pupil, while the retina is responsible for converting light into neural signals, but does not refract light on its own. Therefore, the cornea’s ability to refract light makes it the principal structure for this crucial function in vision.