| Helmholtz theory of accommodation | That the ciliary muscle relaxes for near vision and allows the anterior aspect of the lens to become more convex. (05 Mar 2000) |
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| histologic accommodation | The change in shape of cells to meet altered physical conditions, as the flattening of cuboidal cells in cysts as a result of pressure. Synonym: pseudometaplasia. (05 Mar 2000) |
| host range | The range of host species or cell types which a particular virus, bacteria, or parasite is able to infect or parasitise. (09 Oct 1997) |
| host range mutant | A mutant of phage or animal virus that grows normally in one of its host cells, but has lost the ability to grow in cells of a second host type. (18 Nov 1997) |
| spasm of accommodation | Excessive contraction of the ciliary muscle. (05 Mar 2000) |
| negative accommodation | The decrease of accommodation that occurs when shifting from near vision to distance vision. (05 Mar 2000) |
| normal range | Normal results can fall outside the normal range. By convention, the normal range is set to cover ninety-five percent (95%) of values from a normal population. Five percent (5%) of normal results therefore fall outside the normal range. (12 Dec 1998) |
| dynamic range | <microscopy> In video and other electronic equipment and in photographic emulsions, the ratio of the maximum to minimum signal levels that introduce no more than acceptable levels of signal amplitude distortions. (05 Aug 1998) |
| instrascene dynamic range | <microscopy> The greatest ratio of highlight to shadow brightness to within a single scene that a video camera (tube) can handle usefully. Contrast with the usable light range of a camera, which is considerably greater than the instrascene dynamic range. See: illumination, Kohler. (05 Aug 1998) |
| usable light range | <microscopy> The ratio of the maximum to the minimum levels of illuminance over which a video camera or camera tube can provide a usable signal. Being aided by automatic irises, gray-wedge wheels, etc., in addition to varying electrode voltages where permissible, the usable light range can be several orders of magnitude greater than the intrascene dynamic range. See: intrascene dynamic range, condenser, variable-focus. (05 Aug 1998) |
| limited range audiometer | A pure-tone audiometer designed to test restricted ranges of frequency and sound pressure. (05 Mar 2000) |