What physiological change occurs when the ciliary muscle contracts during accommodation?

When the ciliary muscle contracts during accommodation, the physiological change that occurs is an increase in lens curvature. This process is essential for near vision.

The ciliary muscle is a part of the eye's ciliary body, and its contraction reduces tension on the zonules (suspensory ligaments) that hold the lens in place. As the tension on the zonules decreases, the lens becomes more rounded or convex due to its intrinsic elasticity. This increased curvature allows the lens to refract light more sharply, facilitating clear vision at closer distances.

Understanding the mechanics of accommodation emphasizes the relationship between ciliary muscle contraction, zonular tension, and lens shape. This is fundamental to understanding how the eye adjusts focus for different viewing distances, reflecting the dynamic nature of the visual system.