Accommodation reflex
Accommodation reflex (pronounced: /əˌkɒməˈdeɪʃən rɪˈfleks/) is a reflex action of the eye, in response to focusing on a near object, then looking at a distant object (and vice versa), comprising coordinated changes in Vergence, Lens shape and Pupil size.
Etymology
The term "accommodation reflex" is derived from the Latin words "ad" meaning "to" and "commodare" meaning "make fit", which together imply the eye's ability to adjust or "make fit" its focus to different distances.
Process
The accommodation reflex is initiated when the eye shifts focus from a distant to a near object. This process involves three main responses:
1. Convergence of the eyes: The Extraocular muscles contract to turn the eyes inward, allowing them to focus on the near object.
2. Change in lens shape: The Ciliary muscle contracts, causing the lens to become more rounded, increasing its refractive power to focus on the near object.
3. Constriction of the pupils: The pupils constrict to increase the depth of focus of the eye and reduce spherical aberration.
Related Terms
- Vergence: The simultaneous movement of both eyes in opposite directions to obtain or maintain single binocular vision.
- Lens (anatomy): The transparent elastic structure situated behind the iris of the eye that helps to focus light on the retina.
- Pupil: The adjustable opening in the center of the eye through which light enters.
- Extraocular muscles: The muscles that control the movement of the eyes.
- Ciliary muscle: The circular muscle in the eye that controls the shape of the lens.
See Also
External links
- Medical encyclopedia article on Accommodation reflex
- Wikipedia's article - Accommodation reflex
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