A device for treating an eye affection related to a decrease of ocular accommodation amplitude resulting from loss of tension of the zonular fibers caused by increase in the lens diameter. The device is designed to be surgically implanted in the ciliary sulcus, behind the iris, and configured to compensate the loss of tension of the zonular fibers by exerting on the ciliary sulcus a pressure tending to increase its diameter. The device includes a closed tubular envelope made of an elastic and fluid-impermeable material, the envelope being shaped like a ring or a ring portion having a predetermined outer diameter at rest, the inner ring wall of the envelope delimiting a lumen adapted to be filled with an incompressible fluid tending to increase the outer diameter up to a value whereby the loss of tension of the zonular fibers is compensated.