An accommodating intraocular lens (IOL) device adapted for implantation in the lens capsule of a subject's eye. The IOL device includes an anterior refractive optical element and a membrane coupled to the refractive optical element. The anterior refractive optical element and the membrane define an enclosed cavity configured to contain a fluid. At least a portion of the membrane is configured to contact a posterior area of the lens capsule adjoining the vitreous body of the subject's eye. The fluid contained in the enclosed cavity exerts a deforming or displacing force on the anterior refractive optical element in response to an anterior force exerted on the membrane by the vitreous body. The IOL device may further include a haptic system to position the anterior refractive optical element and also to engage the zonules and ciliary muscles to provide additional means for accommodation.