What is the name of the opening in the iris that allows light into the eye?

The opening in the iris that allows light to enter the eye is known as the pupil. The iris is the colored part of the eye that controls the size of the pupil, adjusting it in response to varying light conditions. When light is bright, the iris constricts the pupil to reduce the amount of light entering the eye, whereas in dim lighting, it dilates the pupil to allow more light in. This mechanism is essential for regulating the amount of light that reaches the retina, which is crucial for optimal vision.

The lens, while an important structure in focusing light onto the retina, does not serve as the opening for light entry. The cornea functions as the eye's outermost layer and plays a significant role in refracting light but is not the opening itself. The retina is the light-sensitive layer at the back of the eye that detects light and sends signals to the brain, but it is not involved in the entry of light. Thus, the pupil is clearly the correct answer, as it directly pertains to the passage of light into the eye.