An electronic device display may have an active area with pixels. An optical sensor may be formed under a sensor region in the active area. During operation, ambient light and/or other light associated with the optical sensor may pass through the sensor region. To ensure that the light for the optical sensor can pass through the display, the display may have one or more layers with sensor openings such as a metal layer and a pressure sensitive adhesive layer that attaches the metal layer to the pixels of the display. To help minimize visibility of the openings in the sensor region, the pressure sensitive adhesive layer may be configured to have a reflectivity that matches the appearance of the display in the sensor region to surrounding areas. Undesired light output uniformity can be reduced by ensuring that the substrate material in the display has a low light absorption coefficient.