Name the parts of the eye involved in light focusing and pupil control.

• A. Cornea and lens focus light; iris controls pupil diameter; ciliary muscles adjust lens shape.
• B. Retina focuses light; optic nerve controls pupil; sclera adjusts lens.
• C. Iris focuses light; pupil controls light; retina adjusts lens.
• D. Lens focuses light; cornea controls pupil; optic chiasm adjusts lens.

Answer: (A)

Light focusing in the eye is accomplished mainly by two structures: the cornea and the lens. The cornea provides most of the eye’s refractive power, bending light as it enters. The lens then fine-tunes that focus by changing its shape, a process controlled by the ciliary muscles—contracting to make the lens thicker for near vision and relaxing for far vision.

Pupil control is managed by the iris, which forms the opening (the pupil). The iris adjusts this opening to regulate how much light reaches the retina, with the muscles in the iris responding to light levels and accommodation needs.

So, the parts involved in both focusing light and adjusting pupil size are the cornea and lens for focusing, the iris for pupil diameter, and the ciliary muscles for changing lens shape. The other structures listed don’t perform these roles: the retina and optic nerve detect light but don’t focus or regulate pupil size; the sclera doesn’t adjust lens; the optic chiasm is a brain structure, not part of lens control.