MRCP UK EXAMINATIONS

Detailed explanation-1: -As the ciliary muscles contract, the suspensory zonules of the lens relax and release the tension of the lens. Thus, somewhat paradoxically, it is the contraction of the ciliary muscles that allows the lens to form a more spherical shape that facilitates accommodation.

Detailed explanation-2: -Contraction of the ciliary muscle loosens the zonular fibers increasing the convexity of the lens, which induces accommodation for near vision.

Detailed explanation-3: -The contraction of the ciliary muscles reduces the tension in the suspensory ligaments and allows the lens to contract into a more spherical shape. This thickening of the lens is called accommodation, and allows light from near objects to be correctly focused on the retina (Fig. 7.7B).

Detailed explanation-4: -When the ciliary muscle is contracted, the lens becomes more spherical – and has increased focussing power – due to a lessening of tension on the zonular fibres (a). When the ciliary muscles relax, these fibres become taut – pulling the lens out into a flatter shape, which has less focussing power (b).