An optical isolation element is provided on an optical sensor comprising a light source, at least one photodetector, and indicator material that emits light that is detected by the photodetector when optically excited by the light source. The optical isolation element limits the optical paths by which light may be transmitted by the light source, thereby limiting exposure of the excitation light source to regions of interest. The optical isolation element also limits the optical paths by which light may be transmitted to the photodetector, thereby limiting exposure of the photodetector to light from extraneous sources.
