A tunable acoustic gradient (TAG) lens includes an acoustic wave generating element and a refractive fluid in a casing cavity surrounded by a lens casing. The lens casing includes case ends which each include a window configuration, a case end rim portion and an enhanced axial compliance portion. The window configuration includes a window and a window mounting portion having an overall window mount dimension along the axial direction. The enhanced axial compliance portion is coupled between the window mounting portion and the case end rim portion and includes a reduced thickness region characterized by a material thickness that is at most 75% of the associated window mount dimension. The axial compliance portion is configured to enhance the axial deflection of the window mounting portion compared to the case end rim portion, when a periodic drive signal is applied to the acoustic wave generating element.