Table of ContentsView AllTable of ContentsAnatomyFunctionAssociated ConditionsDiagnosing Problems
Table of ContentsView All
View All
Table of Contents
Anatomy
Function
Associated Conditions
Diagnosing Problems
The lens is a curved structure in the eye that sits behind theiris. The lens' function is to bend and focus light to help you see images clearly. Because it’s flexible and changes shape, it can help you see objects at varying distances.
As you age, the lens may become weaker or damaged. Since the lens changes shape to focus on images near or far, it can grow weaker and may not work as well later in life.
This article explains the structure of the lens and how it works.
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Anatomy of the Lens
The lens is a clear, curved disk that sits behind the iris and in front of the vitreous of the eye. It is the part of the eye that focuses light and images from the outer world, bending them onto theretina.
Structure
The crystalline lens is a clear, biconvex layer of the eye that is made up mostly of proteins. As much as 60% of the lens mass is made up of proteins—a concentration higher than almost any other tissue in the body.Four structures make up the crystalline lens:
Made up of collagen and proteins, the lens actually has no direct blood or nerve connections. Instead, it relies on the aqueous humor—the clear fluid between the lens and the cornea—to provide it with energy and carry away waste products.
Location
Although the lens is thought to give the eye the most focusing power, the outermost structure of the eye, called thecornea, provides most of the focusing power. Behind the cornea is the iris, which creates a round aperture called the pupil. This pupil changes in size to regulate the amount of light that enters the eye. The crystalline lens sits just behind the iris.
Anatomical Variations
Anatomic variations can exist in the natural lens of the eye. Many different known and unknown congenital diseases can affect the lens in isolation or as part of a syndrome. Most often, these congenital defects present in the form of congenital cataracts or clouding of the crystalline lens.
Most congenital cataracts not associated with a syndrome have no identifiable cause, although genetic mutations are a common reason for cataract presentation. Cataracts at birth can present in one eye (unilaterally) or both eyes (bilaterally). Some of the syndromes associated with congenital cataracts include:
Congenital cataracts may not be evident for some time, progressing until the lens takes on a cloudy color and the child’s sight is impaired. About one-third of congenital cataract cases are hereditary.
Lens' Function
The lens works much like a camera lens, bending and focusing light to produce a clear image. The crystalline lens is a convex lens that creates an inverted image focused on the retina. The brain flips the image back to normal to create what you see around you. In a process called accommodation, the elasticity of the crystalline lens allows you to focus on images at far distances and near with minimal disruption.
Conditions That Affect the Lens
As you age, your natural lens also ages. Its flexibility is slowly lost, and, over time, the lens also becomes opaque, turning the natural clear lens into a cataract.
Cataracts
As lenses become clouded, a condition calledcataractsdevelops. When this condition becomes severe enough to limit or hinder essential activities of daily living, cataract surgery is performed. In this procedure, a prosthetic lens called an intraocular lens replaces the cloudy natural lens. Your eye healthcare provider will be able to determine if there is a cataract and when cataract surgery may be warranted.
Cataract Surgery: Overview
Diagnosing Problems With the Lens
Below are some of the tests your healthcare provider might perform during an eye exam:
What Is an Eye Exam?
Summary
5 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Hejtmancik JF, Shiels A.Overview of the lens.Prog Mol Biol Transl Sci. 2015;134:119-127. doi:10.1016/bs.pmbts.2015.04.006Aliancy J, Mamalis N.Webvision: The organization of the retina and visual system.University of Utah. 2020.American Academy of Opthalmology.Normal crystalline lens.Birth Defect Research for Children.Congenital cataracts.(n.d.)Turbert D.Eye exam and vision testing basics. American Academy of Ophthalmology.
5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Hejtmancik JF, Shiels A.Overview of the lens.Prog Mol Biol Transl Sci. 2015;134:119-127. doi:10.1016/bs.pmbts.2015.04.006Aliancy J, Mamalis N.Webvision: The organization of the retina and visual system.University of Utah. 2020.American Academy of Opthalmology.Normal crystalline lens.Birth Defect Research for Children.Congenital cataracts.(n.d.)Turbert D.Eye exam and vision testing basics. American Academy of Ophthalmology.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Hejtmancik JF, Shiels A.Overview of the lens.Prog Mol Biol Transl Sci. 2015;134:119-127. doi:10.1016/bs.pmbts.2015.04.006Aliancy J, Mamalis N.Webvision: The organization of the retina and visual system.University of Utah. 2020.American Academy of Opthalmology.Normal crystalline lens.Birth Defect Research for Children.Congenital cataracts.(n.d.)Turbert D.Eye exam and vision testing basics. American Academy of Ophthalmology.
Hejtmancik JF, Shiels A.Overview of the lens.Prog Mol Biol Transl Sci. 2015;134:119-127. doi:10.1016/bs.pmbts.2015.04.006
Aliancy J, Mamalis N.Webvision: The organization of the retina and visual system.University of Utah. 2020.
American Academy of Opthalmology.Normal crystalline lens.
Birth Defect Research for Children.Congenital cataracts.(n.d.)
Turbert D.Eye exam and vision testing basics. American Academy of Ophthalmology.
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