OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What is the function of the ciliary body in the eye?

1. To produce and store aqueous humor

2. To alter the shape of the lens

3. To carry impulses to the brain

4. To detect light intensity

The correct answer is: To alter the shape of the lens

The function of the ciliary body in the eye is primarily to alter the shape of the lens. This is accomplished through the action of the ciliary muscles, which are attached to the lens via tiny ligaments called zonules. When the ciliary muscles contract, they relieve tension on the zonules, allowing the lens to become more rounded, which is essential for focusing on near objects. Conversely, when the ciliary muscles relax, the tension increases, flattening the lens for distance vision. This mechanism is crucial for the process of accommodation, enabling the eye to adjust its focus depending on the distance of an object. The ability to change the shape of the lens enhances visual clarity at various distances, making it a vital component in the overall functioning of the eye. Other functions associated with the ciliary body, such as producing aqueous humor, are not its primary role in terms of lens shape adjustment.