Accommodation (from lat. Accommodatio - adaptation, adaptation) - adaptation of an organ or organism as a whole to a change in external conditions (the meaning is close to the term β adaptation β).
Most often, the term is used to describe changes in the refractive power of the optical system of the eye for a clear perception of objects located at different distances. The volume of accommodation describes the limits of the possibility of changing the refractive power of the optical system of the eye for the perception of objects located at different distances [1] . It is determined by the method of A. N. Dashevsky (using negative lenses ), as well as on DKA and PORZ devices .
Physiological accommodation - accommodation of excitable tissues (muscle, nervous), adaptation to the action of a slowly growing force of irritation. Histological accommodation is a change in the shape and ratio of tissue elements (cells) in the process of adaptation to changing conditions [2] .
Content
Links of the accommodation mechanism
- Lens
- Ligamentous lens apparatus (ciliary girdle)
- Ciliary muscle
- Choroid
Accommodation Mechanism
In mammals, it is provided by a change in the curvature of the lens due to contraction and relaxation of the ciliary muscle , and in fish , amphibians and cephalopods , due to the movement of the lens relative to the retina . Birds can use both accommodation mechanisms, then they talk about double accommodation. The theoretical substantiation of eye accommodation was given by the English physicist Thomas Jung (1793) and the German physiologist Helmholtz (1853), whose theory is widely used in ophthalmology.
In humans, through accommodation, accurate adjustment is provided within 5 diopters. With clear vision at each specific distance, the volume of accommodation is divided into two parts: expended and remaining in reserve (reserve).
Accommodation Disorders
Spasm of accommodation
Lowering the reserve of accommodation - the stress of accommodation remaining in the reserve, not involved in visual work with objects located at close range. Removal of the spasm of accommodation is achieved by fairly simple methods, namely, by performing a gymnastics course for the eyes, which in its complex usually implies an improvement not only in accommodation, but also in hemodynamics (blood circulation) in the intraocular vessels, as well as the development of oculomotor muscles. With insufficient effectiveness of gymnastics for the eyes, an ophthalmologist prescribes a course of drug treatment.
Chemical Impairment
Many drugs and toxic substances have the ability to cause disturbance of accommodation.
In studies of the fundus, they resort to drug suppression of accommodation (for example, using such means as cyclomed or atropine , which cause stable pupil dilation and accommodation paralysis).
Notes
- β Fedorova A.Yu., Fedorov Yu.V. // Accommodation stimulators . - Article. - Instrument making. - UDC 535.317
- β Accommodation // Kazakhstan. National Encyclopedia . - Almaty: Kazakh encyclopedias , 2004. - T. I. - ISBN 9965-9389-9-7 .
3. Accommodation: A Guide for Physicians / Ed. L.A. Katargina. - M .: April, 2012 - 136 p., Silt
Links
- Accommodation - article from the Great Soviet Encyclopedia
- Biological Encyclopedic Dictionary / chapters. ed. M.S. Gilyarov. - M .: Soviet Encyclopedia, 1986. - P. 15.
- Accommodation of sight // Brockhaus and Efron Encyclopedic Dictionary : in 86 volumes (82 volumes and 4 additional). - SPb. , 1890-1907.