biconcave lens

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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.
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.

bi·con·cave lens

a lens that is concave on two opposing surfaces.

bi·con·cave lens

(bī-kon'kāv lenz)
A lens that is concave on two opposing surfaces.
Synonym(s): concavoconcave 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-induced uveitis
see phacolytic uveitis, phacoclastic uveitis.
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.
Enlarge picture
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.