| positive lens | <physics> Any lens with a positive focal length. Such lenses are thicker in the centre than around the circumference. There are three types of positive lenses, double convex or biconvex, planoconvex, converging concavoconvex or converging meniscus. (05 Aug 1998) |
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| posterior pole of lens | The central point on the posterior surface of the lens. Synonym: polus posterior lentis. (05 Mar 2000) |
| posterior surface of lens | The posterior surface of the lens of the eye. Synonym: facies posterior lentis. (05 Mar 2000) |
| crystalline 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) |
| cylindrical lens | A lens in which one of the surfaces is curved in one meridian and less curved in the opposite meridian; e.g., a teaspoon or a football. Synonym: astigmatic lens. (05 Mar 2000) |
| safety lens | A lens that meets government specifications of impact resistance; the increased impact resistance required for safety lens's is obtained by tempering, by an ion-exchange process, or by using laminated or plastic lenses. (05 Mar 2000) |
| projection lens | <microscopy> The final lens in the electron microscope. The lens focuses the electrons onto a fluorescent screen to produce the visible image. (05 Aug 1998) |
| slab-off lens | A spectacle lens with a base-up prism below; used in unequal myopia to equalise image displacement when reading. (05 Mar 2000) |
| spherical lens | A lens in which all refracting surfaces are spherical. (05 Mar 2000) |
| spherocylindrical lens | A combined spherical and cylindrical lens, one surface being spherical, the other cylindrical. Synonym: spherocylinder. (05 Mar 2000) |
| negative lens | <physics> A lens with a negative focal length. The edge of a negative lens is thicker than the centre. The three negative lenses are, according to their figure: planoconcave, double concave or biconcave, and diverging concavoconvex or diverging meniscus. See: lens, simple. (05 Aug 1998) |
| substance of lens of eye | That which constitutes the lens of the eye, composed of a nucleus and a cortex and covered by an epithelium. Synonym: substantia lentis. (05 Mar 2000) |
| nucleus of lens | The core or inner dense portion of the lens of the eye. Synonym: nucleus of lens. (05 Mar 2000) |
| decentered lens | A lens so mounted that the visual axis does not pass through the axis of the lens. (05 Mar 2000) |
| suspensory ligament of lens | A series of delicate meridional fibres arising from the inner surface of the orbiculus ciliaris that run in bundles between, and in a very thin layer over, the ciliary processes; at the inner border of the corona, the fibres diverge into two groups that are attached to the capsule on the anterior and posterior surfaces of the lens close to the equator; the spaces between these two layers of fibres are filled with aqueous humor. Synonym: zonula ciliaris, apparatus suspensorius lentis, suspensory ligament of lens, Zinn's zonule. (05 Mar 2000) |