An article includes an optical transforming layer and a guide region positioned inside and adjacent to at least a portion of a perimeter of the optical transforming layer. The guide region comprises an inlet end positioned adjacent to a first surface of the optical transforming layer and an outlet end positioned adjacent a second surface of the optical transforming layer. The guide region propagates light from the inlet end to the outlet end such that the light is directed from the first surface to the second surface. The guide region includes a phase-separated glass comprising a continuous network phase and a discontinuous phase. A relative difference in index of refraction between the continuous network phase and the discontinuous phase is greater than or equal to 0.3%. The discontinuous phase comprises elongated shaped regions aligned along a common axis and having an aspect ratio greater than or equal to 10:1.