An expandable portion of an implant has a total volume and includes a plurality of chambers, each having a volume less than the total volume. The front lens group is formed of a negative meniscus lens with its convex surface on the object side, and a positive meniscus lens with its convex surface on the object side. The reference signal generator selects two phase clock signals according to a digital signal, and adjusts an output ratio of the two phase clock signals in 2M clock periods to serve as a reference clock signal. The first end of each of the plurality of tubular members is fixedly secured to a corresponding one of the plurality of end cap members so as to be vertically extending therefrom.