Crystalline lens (cortex)
Lens (cortex lentis)
Sensory (eye & ear)OrgansHeadLeft and right
View left in 3D View right in 3D
- What it is
- A transparent biconvex lens hung behind the iris by the zonules. It is built of long, tightly packed fibre cells laid down in layers like an onion, with no blood vessels or nerves.
- Function
- Fine-tunes focus (about one-third of the eye's power, ~20 D) by changing shape: it becomes rounder for near vision when the ciliary muscle contracts.
- Size
- 9 mm in diameter and 4 mm thick in an adult; the back surface is more curved than the front.
- Clinical note
- It keeps growing all life and stiffens, causing presbyopia after ~45; clouding of the lens (cataract) is the leading cause of blindness worldwide.