How does the eye adjust the focus of an image on the retina?
The eye adjusts the focus of an image on the retina through a process called accommodation. Accommodation is achieved by changing the shape of the lens within the eye.
To understand how this works, let's first look at the components involved in focusing an image on the retina. The cornea and the lens are responsible for bending light as it enters the eye. The cornea provides most of the focusing power, while the lens fine-tunes the focus.
When we look at objects at different distances, the ciliary muscles surrounding the lens contract or relax to change its shape. This flexibility allows the lens to alter its curvature, which affects its refractive power. When the ciliary muscles contract, the lens becomes thicker, which increases its refractive power for focusing on closer objects. When the ciliary muscles relax, the lens becomes thinner, reducing its refractive power for focusing on distant objects.
To achieve clear vision, the ciliary muscles and lens adjust the shape continuously based on the distance of the object being viewed. This adjustment ensures that light rays from the object converge precisely onto the retina, creating a focused image.
In summary, the eye adjusts the focus of an image on the retina by changing the shape of the lens through the contraction and relaxation of the ciliary muscles. This process is known as accommodation.