Accommodation, Cataract

Definition

Accommodation is a dynamic change in the dioptric power of the eye which is executed in order to focus on targets in different distances.

Mechanism

The accommodative mechanism in its entirety was first described by Helmholtz in 1855. This description is in all relevant aspects still valid. The accommodative apparatus of the eye consists of the ciliary muscle, the zonular fibers forming the suspensory apparatus of the crystalline lens, and the lens itself. According to Helmholtz, during accommodation (focus change far–near) the tension of the zonular fibers which hold the lens in is far-accommodated state decreases as an effect of the contraction of the ciliary muscle and the resulting decrease in size of the ring formed by the ciliary muscle. As a result, the shape of the lens changes under the influence of the elastic lens capsule as it proceeds to its mechanical resting state. This causes an increase in lens curvature and anteroposterior lens thickness and a decrease of...