A method of optically determining a change in magnitude of at least one dimensional characteristic of a sample in response to a selected chamber environment. The modular instrument has an interchangeable hemispherical ball member to properly engage into an acetabular prosthetic socket. The adhesive sheet being arranged to uncover the aperture when exposed to pressure loads. The exit point of the light is disposed next to the device for image deviation in the area of the axially outer end of the lens head. The materials and devices of the present invention are useful in optical communications applications such as intensity and phase modulation, switching, and polarization control. When the actuator arm moves down, it moves a linkage to open a shutter at the base of the housing and simultaneously extends the nozzle through the open shutter.