| FFF | degree of fineness of abrasive particles; field-flow fractionation; flicker fusion frequency |
|---|---|
| FIGE | field inversion gel electrophoresis |
| FIM | field ion microscopy; functional independence measure |
| FOV | field of view |
| FPE | fatal pulmonary embolism; field placement error; final prediction error |
| convexoconcave lens | A minus power lens having one surface convex and the opposite surface concave, with the latter having the greater curvature. (05 Mar 2000) |
|---|---|
| convexoconvex lens | A lens with both surfaces convex. Synonym: convexoconvex lens, double convex lens. (05 Mar 2000) |
| corneal lens | Contact lens of plastic without scleral portions. (05 Mar 2000) |
| cortex of lens | The softer, more superficial part of the lens of the eye that encloses the central part or nucleus; its refractive power is less than that of the nucleus. Synonym: cortex lentis. (05 Mar 2000) |
| 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) |
| 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) |