Lens (anatomy)

Lens (anatomy)

The Lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a sharp real image of the object of interest to be formed on the retina. This adjustment of the lens is known as accommodation.

Diagram of the human eye

Structure

The lens is a transparent biconvex structure, approximately 10mm in diameter, located behind the iris but in front of the vitreous body. It is encased in a thin, transparent capsule and suspended in the eye by the Zonule of Zinn which connects it to the ciliary body.

Function

The primary function of the lens is to focus light onto the retina. It does this by changing its shape in a process called accommodation. When the ciliary muscle contracts, the lens becomes more spherical, increasing its refractive power to focus on near objects. When the ciliary muscle relaxes, the lens becomes more flattened, reducing its refractive power to focus on distant objects.

Clinical significance

Problems with the lens can lead to a number of vision disorders. The most common of these is presbyopia, a condition that results from the loss of elasticity of the lens with age, causing difficulty in focusing on close objects. Another common condition is cataract, which is the clouding of the lens leading to decreased vision.

See also

• Eye
• Accommodation (eye)
• Cataract
• Presbyopia