lens (lenz)
Lens (or crystalline lens)
crystalline lens
lens [lenz]
1. a piece of glass or other transparent material so shaped as to converge or scatter light rays; see also glasses. 
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Lenses: (A–F), Spherical lenses: (A), biconvex; (B), biconcave; (C), planoconvex; (D), planoconcave; (E), concavoconvex, periscopic convex, converging meniscus; (F), convexoconcave, periscopic concave, diverging meniscus; (G, H), cylindrical lenses, concave and convex.
2. crystalline l.; the transparent, biconvex body separating the posterior chamber and vitreous body, and constituting part of the refracting mechanism of the eye.
achromatic lens one corrected for chromatic aberration.
aplanatic lens one for correcting spherical aberrations.
bandage lens a soft contact lens worn on a diseased or injured cornea to protect or treat it.
biconcave lens one concave on both faces.
biconvex lens one convex on both faces.
bifocal lens one with two parts of different refracting powers, the upper for distant and the lower for near vision.
concavoconvex lens one with one concave and one convex face.
contact lens a curved shell of glass or plastic applied directly over the globe or cornea to correct refractive errors. It may be a soft (hydrophilic) contact l., flexible and water absorbent, or a hard (hydrophobic) contact l., rigid and not water absorbent; the latter type is subdivided into gas permeable and non–gas permeable, usually polymethylmethacrylate (PMMA), lenses.
convexoconcave lens one with one convex and one concave face.
crystalline lens lens (2).
cylindrical lens one for correcting astigmatism, with one plane surface and one cylindrical, or one spherical surface and one toroidal. Symbol C.
decentered lens one whose optical axis does not pass through the center.
honeybee lens a magnifying lens resembling the multifaceted eye of the honeybee, consisting of three or six small telescopes mounted in the upper part of the lens and directed toward the center and right and left visual fields. Prisms are included to provide a continuous, unbroken magnified field of view.
omnifocal lens one whose power increases continuously and regularly in a downward direction, avoiding the discontinuity of bifocal and trifocal lenses.
planoconvex lens a lens with one plane and one convex side.
spherical lens (S) (sph) one that is a segment of a sphere.
trial lens one used to test vision.
trifocal lens one with three parts of different refracting powers, the upper for distant, the middle for intermediate, and the lower for near vision.
Lens (or crystalline lens)
The eye structure behind the iris and pupil that helps focus light on the retina.
Mentioned in: Presbyopia
crystalline lens
[kris′təlin, -līn]
Etymology: Gk, krystallos + L, lentil
a transparent structure of the eye, enclosed in a capsule, situated between the iris and the vitreous humor, and slightly overlapped at its margin by the ciliary processes. It refracts light to focus images on the retina. The capsule of the lens is a transparent elastic membrane that touches the free border of the iris anteriorly and is secured by the suspensory ligament of the lens. The circumference of the capsule recedes from the iris to form the posterior chamber of the eye. The lens is a transparent biconvex structure with the posterior surface more convex than the anterior, derived from surface ectoderm. It is composed of a soft cortical material, a firm nucleus, and concentric laminae and is covered anteriorly by transparent epithelium. In the fetus the lens is very soft and has a slightly reddish tint; in the adult it is colorless and firm; in old age it becomes flattened, more dense, slightly opaque, and amber-tinted. See also eye.
lens [lenz]
1. a piece of glass or other transparent material so shaped as to converge or scatter light rays. See also glasses.
2. the transparent, biconvex body separating the posterior chamber and the vitreous body of the eye; it refracts (bends) light rays so that they are focused on the retina. Called also crystalline lens. In order for the eye to see objects close at hand, light rays from the objects must be bent more sharply to bring them to focus on the retina; light rays from distant objects require much less refraction. It is the function of the lens to do accommodation, making of adjustments for viewing both near objects and more distant ones. To accomplish this it must be highly elastic so that its shape can be changed and made more or less convex. The more convex the lens, the greater the refraction. Small ciliary muscles create tension on the lens, making it less convex; as the tension is relaxed the lens becomes more spherical in shape and hence more convex.
With increasing age the lenses lose their elasticity; thus their ability to focus light rays in the retina becomes impaired. This condition is called presbyopia. In farsightedness (hyperopia) the image is focused behind the retina because the refractive power of the lens is too weak or the eyeball axis is too short. Nearsightedness (myopia) occurs when the refractive power of the lens is too strong or the eyeball is too long, so that the image is focused in front of the retina.
With increasing age the lenses lose their elasticity; thus their ability to focus light rays in the retina becomes impaired. This condition is called presbyopia. In farsightedness (hyperopia) the image is focused behind the retina because the refractive power of the lens is too weak or the eyeball axis is too short. Nearsightedness (myopia) occurs when the refractive power of the lens is too strong or the eyeball is too long, so that the image is focused in front of the retina.
The biconvex lens of the eye. From Frazier et al., 1996.
achromatic lens one corrected for chromatic (color) aberration.
apochromatic lens one corrected for chromatic (color) and spheric aberration.
biconcave lens one concave on both faces.
biconvex lens one convex on both faces.
bifocal lens one having two segments with different refracting power, the upper for far vision and the lower for near vision. See also bifocal glasses.
concave lens one curved like a section of the interior of a hollow sphere; it disperses light rays. Called also diverging lens.
contact l's corrective lenses that fit directly over the cornea of the eye; see also contact lenses.
converging lens (convex lens) one curved like the exterior of a hollow sphere; it brings light to a focus.
convexoconcave lens one that has one convex and one concave face.
crystalline lens lens (def. 2).
cylindrical lens one with at least one nonspherical surface, used to correct astigmatism.
diverging lens concave lens.
honeybee lens a magnifying eyeglass lens designed to resemble the multifaceted eye of the honeybee. It consists of three or six small telescopes mounted in the upper portion, directed toward the center and right and left visual fields. Prisms are included to provide a continuous, unbroken magnified field of view.
omnifocal lens one whose power increases continuously and regularly in a downward direction, avoiding the discontinuity in field and power inherent in bifocal and trifocal lenses.
orthoscopic lens one that gives a flat and undistorted field of vision, especially at the periphery.
planoconcave lens a lens with one plane and one concave side.
planoconvex lens a lens with one plane and one convex side.
Stokes's l's an apparatus used in the diagnosis of astigmatism.
trial l's ones used in testing the vision.
trifocal lens one having three segments of different refracting powers, the upper for distant, the middle for intermediate, and the lower for near vision.
crystalline
1. resembling a crystal in nature or clearness.
2. pertaining to crystals.
crystalline lens
the transparent organ behind the pupil of the eye. See also lens.
lens
1. a piece of glass or other transparent material so shaped as to converge or scatter light rays.
2. crystalline lens; the transparent, biconvex body separating the posterior chamber and the vitreous body of the eye. The crystalline lens refracts (bends) light rays so that they are focused on the retina. In order for the eye to see objects close at hand, light rays from the objects must be bent more sharply to bring them to focus on the retina. See also lenticular.
apochromatic lens
one corrected for both chromatic and spherical aberration.
biconcave lens
one concave on both faces.
biconvex lens
one convex on both faces.
lens cells
the only nucleated cells in the lens of the adult are those of the epithelium beneath the capsule on the rostral surface.
concave lens
one with one or both (biconvex) faces curved like a section of the interior of a hollow sphere; it disperses light rays. Called also dispersing lens.
contact l's
lenses that fit directly over the cornea of the eye; used in humans for correction of refractive errors but only rarely applied in animals and then for therapeutic purposes. They can be applied in cases of severe bullous keratopathy or, after saturation with antibiotic solution, the delivery of antibiotics in high concentration to the cornea.
converging lens
one curved like the exterior of a hollow sphere; it brings light to a focus. Called also convex lens.
convex lens
see converging lens (above).
convexoconcave lens
one that has one convex and one concave face.
crystalline lens
see lens (2) (above).
dispersing lens
concave lens.
ectopic lens
see ectopia lentis.
lens fibers
elongated, modified cells oriented meridianly in concentric layers; the most peripheral contain nuclei; they interlock with each other via the medium of ball and socket interdigitations and flaps and imprints.
lens induction
see inductive interactions.
intraocular lens
plastic lenses placed within the lens capsule after cataract surgery.
intumescent lens
see intumescent cataract.
lens luxation
separation of the lens from its zonular attachments, allowing displacement and freedom to move in the posterior chamber, anterior chamber or occasionally the vitreous. Occurs most commonly in dogs and is a result of trauma or as a familial trait, particularly in wirehaired Fox terriers and Sealyham terriers, predisposing to glaucoma. Luxation can occur secondary to space-occupying intraocular tumors, enlargement of the globe in chronic glaucoma, or swelling of the lens as seen in intumescent cataract.
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Lens luxation in a horse's eye. By permission from Knottenbelt DC, Pascoe RR, Diseases and Disorders of the Horse, Saunders, 2003
lens opacity
cataract.
lens sclerosis
see nuclear sclerosis.
lens subluxation
partial separation of zonular attachments, allowing some alteration in position but not movement into another chamber.
lens sutures
structures formed by the contact between caudal and rostral lens fibers resulting in Y-shaped lens stars.
Patient discussion about crystalline lens.
Q. My neighbor's kid had a lens dislocation due to Marfan's disease. Is this a contagious thing? My neighbor's have a sweet 8 year old boy. he had a lens dislocation due to a connective tissue disease named Marfan (I think that the name). It sounds like a very serious condition. My boy is playing with this kid several hour a week. should I take him to the GP to see that his is not infected with this marfan thing?
A. Don't worry. Marfan's syndrome is a connective tissue disease that is genetic. This means that You can't "get" this disease. Either you are borne with it or you will never suffer from it.
lens dislocation is a known symptom of marfan's syndrome, and is not connected to infectious diseases.
Read more or ask a question about crystalline lenslens dislocation is a known symptom of marfan's syndrome, and is not connected to infectious diseases.
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