An optical combiner includes a lightguide having an input region, an output region, a relay region intermediate between the input region and the output region, and one or more stress raisers positioned to define a line of weakness in the lightguide. The line of weakness is intermediate between the input region and the output region and extends across the relay region. An in-coupler is disposed at the input region to receive an incident light with a field of view and couple the incident light into the lightguide. An out-coupler is disposed at the output region to couple light out of the lightguide. The optical combiner may be integrated with one or more lenses for use as a combiner lens in a wearable heads-up display.