| toric lens | A lens in which both meridians are curved but not to the same degree. (05 Mar 2000) |
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| trifocal lens | A lens with segments of three focal powers: distant, intermediate, and near. (05 Mar 2000) |
| epithelium of lens | The layer of cuboidal cells lying on the anterior surface of the crystalline lens inside the lens capsule. at the equator the cells elongate and give rise to the lens fibres. Synonym: epithelium lentis. (05 Mar 2000) |
| equator of lens | The periphery of the lens lying between the two layers of the ciliary zonule. Synonym: equator lentis. (05 Mar 2000) |
| exfoliation of lens | Sheetlike separation of the capsule of the lens; it may occur if the eyes are exposed to intense heat. (05 Mar 2000) |
| eye lens | <physics> The lens nearest the eye in any ocular. (05 Aug 1998) |
| fibres of lens | <biology, ophthalmology, physiology> The elongated cells of ectodermal origin forming the substance of the crystalline lens of the eye. Synonym: fibrae lentis. (05 Mar 2000) |
| field lens | <physics> The lower lens in an ocular, the lens nearest the object field. (05 Aug 1998) |
| lamina of lens | One of a series of concentric layers composed of the lens fibres that make up the substance of the lens. (05 Mar 2000) |
| Fresnel lens | <physics> A lens built up, progressively, in zones or steps, each zone with its own individual radius. Considerable spherical correction is attained, and the weight of the lens is greatly reduced. Fresnel lenses were originally designed for lighthouses but they are now attainable for small spotlights, automobile headlights, and similar uses. (05 Aug 1998) |
| front lens | <physics> The front element of a compound lens system, the first lens element which the entering light encounters. See: back lens. (05 Aug 1998) |
| lens | <physics> A transparent optical element, so constructed that it serves to change the degree of convergence or divergence of the transmitted rays. (05 Aug 1998) |
| lens, Bertrand | <microscopy> A small convergent lens placed between objectives and eyepiece. The lens focuses an image of the upper focal plane of the objective on the focal plane of the eyepiece. It is chiefly used with polarized light for inspecting the interference figure. It is also convenient for quickly verifying centreing, size, and uniform illumination of an aperture. (05 Aug 1998) |
| lens capsule | The capsule enclosing the lens of the eye. Synonym: capsula lentis, crystalline capsule, lenticular capsule, phacocyst. (05 Mar 2000) |
| lens capsule, crystalline | The noncellular outer covering of the crystalline lens, secreted by the embryonic anterior and posterior epithelium. The embryonic posterior epithelium later disappears. (12 Dec 1998) |