The invention improves the optical transmission of a light guide assembly in an optical illumination apparatus achieved by one or more insulation layers which sheath a rigid or flexible light guide rod of the light guide assembly andor the coupling of light emitted from a radiation source into the light input surface of the light guide rod is improved by an adapter element. Embodiments of the invention incorporate a surround portion and a casing portion, and use an opposing pair of biased clip members to retain the trim assembly in the window opening and to automatically center the trim assembly therein. Compounds immobilized on the substrates and compounds for preparing such substrates include antimicrobial andor anti-inflammatory compounds according to Formulas, ,, ,, , and described herein. The original and the shifted images are then interspersed together, yielding an interpolated image. The axial aperture has two flat inner surfaces for cooperating with the two flat sections of the threaded body portion to prevent relative rotation of the washer and threaded body portion. When measuring the object during a surface machining, the reject thresholds are progressively and automatically updated as a function of a gradual thickness reduction that the object undergoes.