When light enters the eye, the first structure it passes through is the?

When light enters the eye, the first structure it encounters is the cornea. The cornea is a transparent, dome-shaped surface that covers the front part of the eye and is primarily responsible for the eye's ability to focus light properly. Its curvature bends the incoming light rays, allowing them to pass through the pupil and into the deeper structures of the eye for further processing.

The pupils are openings that control the amount of light entering the eye, but they are not the first structure light passes through. The lens, located behind the pupil, further refines the focus of the light but comes into play after the cornea. The retina, at the back of the eye, is where light is ultimately processed into visual information, but it is the last stop for light in the eye's pathway.

Therefore, the cornea serves as the initial barrier through which light must pass, making it the correct answer in this context.