Which layer of the eye contains millions of photoreceptors for image detection?

The retina is the correct choice because it is the specialized layer of the eye that contains millions of photoreceptor cells, specifically rods and cones, which are essential for detecting light and creating visual images. The rods are primarily responsible for vision in low-light conditions, while the cones are responsible for color vision and function best in bright light. The arrangement of these photoreceptors allows the retina to convert light into neural signals, which are then processed by the brain to form images.

In contrast, the cornea is the transparent front layer of the eye that helps to focus light but does not contain photoreceptors. The iris is the colored part of the eye that controls the size of the pupil and the amount of light entering the eye, but it also does not contain photoreceptors. The pupil itself is an opening that regulates the light entering the eye, but like the iris and cornea, it lacks the photoreceptor cells necessary for image detection.