An electronic device has an electrically adjustable optical layer. Displays and other optical components may be supported by a housing structure. The housing structure may form a handheld device housing, a head-mounted housing, or other housing for the electronic device. Control circuitry in the electronic device may adjust the electrically adjustable optical layer. The control circuitry may reduce light transmission for the electrically adjustable optical layer to hide the optical components, may increase light transmission to reveal the optical components while the optical components are being used to receive light or to output light, and may otherwise adjust the electrically adjustable optical layer to exhibit a desired set of optical characteristics depending on the mode of operation of the electronic device.