accommodation

(redirected from accommodations)
Also found in: Dictionary, Thesaurus, Medical, Legal, Financial.

accommodation

Physiol the automatic or voluntary adjustment of the shape of the lens of the eye for far or near vision

accommodation

  1. (in race relations) a process in which ethnic groups adjust to each other's existence and coexist without necessarily resolving underlying differences and conflicts (compare ASSIMILATION).
  2. (more generally, e.g. in politics or in domestic life) any individual or group behaviour of the above kind.
  3. (as used by the CHICAGO SCHOOL, e.g. PARK and Burgess, 1921) a fundamental social process, analogous to biological adaptation, by which societies achieve adjustment to 4 (in PIEGET's theory of CHILD DEVELOPMENT) one of the mechanisms by which development from one stage to the next is achieved. See ASSIMILATION AND ACCOMMODATION.

Accommodation

 

a term used in biology and medicine, similar to “adaptation.” The term is traditionally used in the three phrases “accommodation of the eye,” “physiological accommodation,” and “histological accommodation.”

Accommodation of the eye is adaptation of the eye in order to obtain clear vision of objects at various distances. It is achieved by a change in the refractive power of the optical system, which leads to the focusing of the image on the retina. In fish the eye is constructed for close vision, and accommodation is achieved by the rearward displacement of the spherical crystalline lens. In amphibians and reptiles the eye at rest is constructed for distant vision, and accommodation is achieved by the forward movement of the crystalline lens. In birds, mammals, and humans accommodation is achieved by a change in the curvature of the crystalline lens. Accommodation is performed by the accommodation muscles and is possible within certain limits—that is, when the object is at a particular distance from the eye within the field between the points of close and distant vision.

When the intraocular, so-called accommodation muscles contract, the ligaments are relaxed and the crystalline lens suspended on them becomes more protuberant. An increase in the curvature of the crystalline lens leads to a stronger refraction, in consequence of which it becomes possible for the eye to focus the light rays emanating from closely placed objects on the retina and to see them clearly.

The physical factor of crystalline lens elasticity also enters into eye accommodation. In humans the ability of the accommodation muscles to contract and the elasticity of the crystalline lens may change because of a number of conditions. Accommodation is most highly developed in children. With age, elasticity of the crystalline lens diminishes, the ability to see close objects decreases, and so-called senile vision, or presbyopia, develops. Signs of diminution of eye accommodation in persons with normal refraction (emmetropia) appear most commonly between the ages of 40 and 45. When such diminution of eye accommodation occurs, glasses with convex lenses are prescribed for close work (reading and writing) to compensate for the defect. Subsequently, the strength of the eyeglass lenses is gradually increased; by the age of 60 or 70 eye accommodation is usually entirely lost and it is no longer necessary to increase the strength of the eyeglass lenses. Spasm of the accommodation muscles may occur as a result of prolonged eyestrain, bright light, eye trauma, or other factors. Paralysis of these muscles may occur with certain infections and intoxications—for example, syphilis, influenza, diabetes, diphtheria, and botulism. The treatment of spasm or paralysis depends on the cause.

Physiological accommodation, or accommodation of excited muscular or neural tissue, is adaptation to the action of a slowly intensifying stimulus. For example, rapid chilling or a blow may excite an isolated nerve fiber, whereas slow cooling or gradual pressure may not. The same thing is observed with electrical stimulation; with the slow intensification of current, the action potential of a nerve or muscle does not emerge. Such accommodation is associated with active changes in the tissue that raise the threshold of irritability and obstruct the development of excitation.

Histological accommodation, or tissue accommodation, is a change in the forms and relationships of tissue elements (cells) in the process of adaptation to changed conditions. An example of histological accommodation is the transformation of the cubical epithelium of the glomerular capsule into long cylindrical cells when the volume of the glomerulus decreases. However, histological accommodation is often difficult to differentiate from other processes, such as metaplasia and atrophy. The term is therefore merely a formal one.

REFERENCES

Dashevskii, A. I. “Refraktsiia i akkomodatsiia glaza.” In Mnogotomnoe rukovodstvo po glaznym bolezniam, vol. 1, book 1. Edited by V. N. Arkhangel’skii. Moscow, 1962.
Fiziologiia cheloveka. Edited by E. B. Babskii. Moscow, 1966.

M. L. KRASNOV and S. P. LANDAU

accommodation

[ə‚käm·ə′dā·shən]
(control systems)
Any alteration in a robot's motion in response to the robot's environment; it may be active or passive.
(ecology)
A population's location within a habitat.
(mapping)
The limits or range within which a stereo-plotting instrument is capable of operating.
(physiology)
A process in most vertebrates whereby the focal length of the eye is changed by automatic adjustment of the lens to bring images of objects from various distances into focus on the retina.

accommodation

accommodationclick for a larger image
Accommodation: adjustment of eye focus on distant object (left) and close object (right).
i. The ability of the human eye to adjust itself to give sharp images for different object distances. It is the process by which the lens of the eye can be flattened to focus distant points on the retina or made more convex to focus nearby points on the retina.
ii. The limits or range within which a stereo-plotting instrument is capable of operating. For example, a multiplex stereograph can adjust or accommodate for small tilts in the projector, ranging from approximately 10° about the X-axis to 20° about the Y-axis.
References in classic literature ?
I believe I have lived as much on board as most women, and I know nothing superior to the accommodations of a man-of-war.
I believe the reader of this will not think it strange if I confess that these anxieties, these constant dangers I lived in, and the concern that was now upon me, put an end to all invention, and to all the contrivances that I had laid for my future accommodations and conveniences.
I looked upon all three bills, and smiled, and told her I did not see but that she was very reasonable in her demands, all things considered, and for that I did not doubt but her accommodations were good.
He must be a horseman of good quality to have such accommodations.
Pickwick's short experience of the accommodations of the Great White Horse had led him to expect.
As the travellers had observed that day many indications of their drawing nearer and nearer to the race town, such as gipsy camps, carts laden with gambling booths and their appurtenances, itinerant showmen of various kinds, and beggars and trampers of every degree, all wending their way in the same direction, Mr Codlin was fearful of finding the accommodations forestalled; this fear increasing as he diminished the distance between himself and the hostelry, he quickened his pace, and notwithstanding the burden he had to carry, maintained a round trot until he reached the threshold.
We might have managed to put the man somewhere, if he'd been alone, but these women want family accommodation.
Now as this law, under a modified form, is to this day in force in England; and as it offers in various respects a strange anomaly touching the general law of Fast and Loose-Fish, it is here treated of in a separate chapter, on the same courteous principle that prompts the English railways to be at the expense of a separate car, specially reserved for the accommodation of royalty.
There was accommodation for many horses and carriages; but I need only describe the stable into which I was taken; this was very roomy, with four good stalls; a large swinging window opened into the yard, which made it pleasant and airy.
The letter was from this gentleman himself, and written in the true spirit of friendly accommodation.
The travelers reached London in good time that evening, and found accommodation at the hotel.
From their original inch or so of private handwriting they have spread and spread out across the world, and now whole generations of men find intellectual accommodation within them,--drinking fountains and other public institutions are erected upon them; yea, Carlyle has become a Chelsea swimming-bath, and "Highland Mary" is sold for whiskey, while Mr.