| amplitude of accommodation | The difference in refractivity of the eye at rest and when fully accommodated. (05 Mar 2000) |
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| amplitude | 1. State of being ample; extent of surface or space; largeness of dimensions; size. "The cathedral of Lincoln . . . Is a magnificent structure, proportionable to the amplitude of the diocese." (Fuller) 2. Largeness, in a figurative sense; breadth; abundance; fullness. Of extent of capacity or intellectual powers. "Amplitude of mind." . "Amplitude of comprehension." . Of extent of means or resources. "Amplitude of reward." . 3. <astronomy> The arc of the horizon between the true east or west point and the center of the sun, or a star, at its rising or setting. At the rising, the amplitude is eastern or ortive: at the setting, it is western, occiduous, or occasive. It is also northern or southern, when north or south of the equator. The arc of the horizon between the true east or west point and the foot of the vertical circle passing through any star or object. 4. The horizontal line which measures the distance to which a projectile is thrown; the range. 5. <physics> The extent of a movement measured from the starting point or position of equilibrium; applied especially to vibratory movements. 6. <mathematics> An angle upon which the value of some function depends; a term used more especially in connection with elliptic functions. Magnetic amplitude, the angular distance of a heavenly body, when on the horizon, from the magnetic east or west point as indicated by the compass. The difference between the magnetic and the true or astronomical amplitude (see 3 above) is the "variation of the compass." Origin: L. Amplitudo, fr. Amplus: cf. F. Amplitude. See Ample. Source: Websters Dictionary (01 Mar 1998) |
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| amplitude of convergence | The distance between the near point and far point of convergence. Synonym: range of convergence. (05 Mar 2000) |
| amplitude of pulse | See: average pulse magnitude, peak magnitude. (05 Mar 2000) |
| phase-amplitude contrast | <microscopy> The separation and recombination of direct vs. Diffracted rays in a light microscope adjusted to Kohler illumination. at the lower focal plane of the condenser there is an annular diaphragm with an opaque central stop. Through this diaphragm rays are focused as a hollow cone onto the specimen. In the back focal plane of the objective there is a conjugate annular diaphragm (phase plate). If here the undiffracted rays are retarded (by a transparent film of proper thickness on the annulus of the phase plate), bright contrast results. If, instead, the phase-delay film is on the central spot, dark contrast results. With either a bright or a dark-contrast phase plate, the annulus is usually coated with a partially absorbing (very thin) film of silver (Zernike method) or carbon soot (Wilska method) to reduce the higher amplitude (intensity) of the undiffracted rays. (05 Aug 1998) |
| minimal amplitude nystagmus | Nystagmus of so small an amplitude that it is not detected by the usual clinical tests. Synonym: minimal amplitude nystagmus. Origin: micro-+ G. Nystagmos, a nodding (05 Mar 2000) |
| half amplitude pulse duration | The time, in milliseconds, required for a wave form to reach half of its full magnitude. (05 Mar 2000) |
| tidal amplitude | The magnitude of the difference in elevation between low and high tides at a particular point in a body of water. (09 Oct 1997) |
| accommodation | <ophthalmology, physiology> Adjustment, especially that of the eye for various distances resulting in pupil constriction or dilatation. Origin: L. Accommodare = to fit to (18 Nov 1997) |
| accommodation, ocular | The dioptric adjustment of the eye (to attain maximal sharpness of retinal imagery for an object of regard) referring to the ability, to the mechanism, or to the process. It is the effecting of refractive changes by changes in the shape of the crystalline lens. Loosely, it refers to ocular adjustments for vision at various distances. (12 Dec 1998) |
| accommodation of eye | The increase in thickness and convexity of the eye's lens in order to focus the image of an external object upon the retina. (05 Mar 2000) |
| accommodation of nerve | <anatomy, nerve> The property of a nerve by which it adjusts to a slowly increasing strength of stimulus, so that its threshold of excitation is greater than it would be were the stimulus strength to have risen more rapidly. (05 Mar 2000) |
| accommodation reflex | Increased convexity of the lens, due to contraction of the ciliary muscle and relaxation of the suspensory ligament, to maintain a distinct retinal image. (05 Mar 2000) |
| accommodative convergence-accommodation ratio | The amount of convergence (measured in prism diopters of convergence) divided by the amount of accommodation (measured in diopters) required to direct both eyes upon an object. (05 Mar 2000) |
| range of accommodation | The distance between an object viewed with minimal refractivity of the eye and one viewed with maximal accommodation. (05 Mar 2000) |
| relative accommodation | Quantity of accommodation required for single binocular vision for any specified distance, or for any particular degree of convergence. (05 Mar 2000) |