A 50-year-old man came to the ophthalmologist with the complaint of inability to read newspaper. His vision problem is likely due to inadequate contraction of which of the following structures?

The process by which the curvature of the lens is increased is called accommodation.If the gaze is directed at a near object, the ciliary muscle contracts. This decreases the distance between the edges of the ciliary body and relaxes the lens ligaments so that the lens springs into a more convex shape. By the time a healthy individual reaches age 40-45 years, the loss of accommodation is usually sufficient to make reading and close work difficult. This condition, which is known as presbyopia, can be corrected by wearing glasses with convex lenses.