Crystalline lens
Crystalline Lens
The Crystalline Lens (pronounced: kris-tuh-leen lenz) 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.
Etymology
The term "crystalline lens" is derived from the Latin word "crystallinus" meaning "crystal clear" and the Old French word "lentille" meaning "lens". The term was coined due to the lens's crystal-clear transparency.
Structure
The crystalline lens is located in the eye behind the iris but in front of the vitreous body. It is suspended in place by the zonule fibers which are attached to the ciliary body. The lens is composed of a central part, the lens nucleus, and an outer part, the lens cortex. The lens is enclosed in a thin transparent capsule, the lens capsule.
Function
The primary function of the crystalline lens is to focus light onto the retina. It does this by changing its shape, a process known as accommodation. When the ciliary muscle contracts, the lens becomes more spherical, increasing its power to focus incoming light. When the ciliary muscle relaxes, the lens becomes more flattened, decreasing its power.
Related Terms
- Accommodation (eye): The process by which the eye changes optical power to maintain a clear image or focus on an object as its distance varies.
- Ciliary body: The part of the eye that produces aqueous humor and controls accommodation by changing the shape of the crystalline lens.
- Lens nucleus: The central part of the lens.
- Lens cortex: The outer part of the lens.
- Lens capsule: The thin transparent membrane that encloses the lens.
- Zonule fibers: The fibers that suspend the lens in place.
External links
- Medical encyclopedia article on Crystalline lens
- Wikipedia's article - Crystalline lens
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