Lens (vertebrate anatomy)

Lens (Vertebrate 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 length 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.

Function

The primary function of the lens is to bend and focus light to create a sharp image on the retina. The lens accomplishes this by changing its shape, a process known as accommodation. When the ciliary muscle contracts, the lens thickens, increasing its ability to focus close-up images on the retina. When the ciliary muscle relaxes, the lens thins, allowing it to focus on distant objects.

Clinical significance

The lens can be affected by several diseases and conditions. Cataract, a clouding of the lens, is the most common. Other conditions include Presbyopia, a condition associated with aging where the lens hardens and loses its ability to focus on close objects, and Aphakia, a condition where the lens is either missing or damaged.

See also

• Eye
• Retina
• Cornea
• Iris
• Vitreous body
• Zonule of Zinn
• Cataract
• Presbyopia
• Aphakia