Accommodation

(ak-om-o-da’ -shun) [accommodare, to adjust]. Adaptation or adjustment, particularly the adjustment of the eye for different distances. A., Absolute, the accommodation of either eye separately. _ A., Histologic, the occurrence of changes in the morphology and function of cells following changed conditions. A., Negative, the condition of the eye at rest. A. of the Eye, that function of the ciliary muscle and lens whereby objects at different distances are clearly seen. It depends upon the inherent elasticity of the lens, which when the ciliary muscle of an emmetropic eye is at rest, is adapted to the proper focalization of theoretically parallel rays of light. Objects nearer, to be clearly seen, require a greater refracting power on the part of the eye because the rays from such objects are more divergent. This additional refracting power is gained by an increased antero-posterior diameter of the lens, brought about by the contraction of the ciliary muscle, which occasions a loosening of the suspensory ligament and a thickening of the lens by its own elasticity. A. Phosphenes, the peripheral light-streak seen in the dark aiter the act of accommodation. A., Range of, the distance between the nearest point of distinct vision, and the most distant point. 24