How does the eye let in light?

The eye lets in light through the cornea, which is the transparent outer layer that bends light rays. The light then passes through the pupil, the adjustable opening controlled by the iris, which regulates the amount of light entering. After the pupil, light is further focused by the lens onto the retina at the back of the eye, where photoreceptor cells convert the light into electrical signals for the brain to interpret.