An external device is provided for use with an intraocular device configured to be implanted entirely in an eye of a subject. The external device includes a mount configured to be placed in front of the eye and a sensor coupled to the mount and configured to sense a level of ambient light. The external device additionally includes an external power source coupled to the mount and configured to (i) emit toward the eye non-visible light that is outside of 380-750 nm, and (ii) modulate the non-visible light based on the level of ambient light sensed by the sensor. Other application are also described.