Sealed precision optical assemblies are provided by a mold-in-place (MIP) process wherein a glass preform for a lens or other optical element is molded and sealed directly into a one-piece metal support for the element in a single precision molding step. The product is a sealed glass/metal assembly incorporating a non-interlocking mechanical seal, the seal being hermetic yet free of supplemental sealing materials, and the optical axis of the glass element being at a precise predetermined location and in a predetermined alignment relative to one or more reference surfaces on the metal support.