Which transparent structure behind the pupil changes shape to help focus images on the retina?

• A. Cornea
• B. Lens
• C. Iris
• D. Retina

Answer: (B)

The lens is the adjustable, transparent structure behind the pupil that changes shape to focus images on the retina. When you look at something close, the ciliary muscle contracts and the suspensory ligaments loosen, allowing the lens to become more spherical and increase its refractive power so light focuses on the retina. For distant vision, the ciliary muscle relaxes, the ligaments pull the lens into a flatter shape, and its focusing power decreases. The cornea provides most of the eye’s refraction but its shape is relatively fixed, so the lens does the fine-tuning needed to form a clear image on the retina. The iris simply controls how much light enters, and the retina is where the image is finally projected.