How does the lens of the eye change shape for focusing?

The lens of the eye changes shape for focusing through a process called accommodation, controlled by the ciliary muscles.

In more detail, the lens of the eye is a flexible, transparent structure that plays a crucial role in focusing light onto the retina, the light-sensitive tissue at the back of the eye. This process of focusing is known as accommodation. The lens is able to change its shape thanks to its elastic properties and the action of the surrounding ciliary muscles.

The ciliary muscles are a ring of smooth muscle fibres in the eye's middle layer, or uvea. When these muscles contract, they reduce the tension on the lens, allowing it to become more rounded for close-up focus. Conversely, when the ciliary muscles relax, they increase the tension on the lens, causing it to flatten for distant focus. This change in lens shape alters its refractive power, enabling it to focus light from objects at various distances onto the retina.

The lens's ability to change shape is also influenced by its composition. It is made up of layers of transparent, flexible proteins called crystallins. These proteins are arranged in a precise manner that allows the lens to alter its shape while maintaining its transparency, which is essential for clear vision.

In summary, the lens of the eye changes shape for focusing through a process called accommodation, which is controlled by the ciliary muscles. This process is crucial for our ability to see objects clearly at different distances.