A computer implemented method for execution on a head-mounted device (102, 200, 402, 704, 2700) including an image sensing system, which comprises the steps of: controlling a plurality of light sources (302, 1202) of a handheld object (106, 202, 300, 406, 408, 702); acquiring, via the image sensing system, image data of a surrounding environment, the image data comprising a sequence of environmental tracking exposures in which the plurality of light sources are controlled to have a lower integrated intensity and handheld object tracking exposures in which the plurality of light sources are controlled to have a higher integrated intensity; detecting, via an environmental tracking exposure, one or more features of the surrounding environment; determining a pose of the head-mounted device based upon the one or more features of the surrounding environment detected; detecting, via a handheld object tracking exposure, the plurality of light sources of the handheld object; determining a pose of the handheld object based upon the plurality of light sources detected and the world pose of the HMD as based on the one or more features of the surrounding environment detected; outputting the pose of the handheld object determined, and further comprising the steps of: determining whether the handheld object is detectable in one or more handheld object tracking exposures; and based upon the handheld object not being detectable in the one or more handheld object tracking exposures, performing using the plurality of light sources (302, 1202) an optical time synchronization between a clock domain of the head-mounted device and a clock domain of the handheld object in order to correct the relative timing of environmental tracking exposures and handheld object tracking exposures. controlling a plurality of light sources (302, 1202) of a handheld object (106, 202, 300, 406, 408, 702); acquiring, via the image sensing system, image data of a surrounding environment, the image data comprising a sequence of environmental tracking exposures in which the plurality of light sources are controlled to have a lower integrated intensity and handheld object tracking exposures in which the plurality of light sources are controlled to have a higher integrated intensity; detecting, via an environmental tracking exposure, one or more features of the surrounding environment; determining a pose of the head-mounted device based upon the one or more features of the surrounding environment detected; detecting, via a handheld object tracking exposure, the plurality of light sources of the handheld object; determining a pose of the handheld object based upon the plurality of light sources detected and the world pose of the HMD as based on the one or more features of the surrounding environment detected; outputting the pose of the handheld object determined, and further comprising the steps of: determining whether the handheld object is detectable in one or more handheld object tracking exposures; and based upon the handheld object not being detectable in the one or more handheld object tracking exposures, performing using the plurality of light sources (302, 1202) an optical time synchronization between a clock domain of the head-mounted device and a clock domain of the handheld object in order to correct the relative timing of environmental tracking exposures and handheld object tracking exposures. determining whether the handheld object is detectable in one or more handheld object tracking exposures; and based upon the handheld object not being detectable in the one or more handheld object tracking exposures, performing using the plurality of light sources (302, 1202) an optical time synchronization between a clock domain of the head-mounted device and a clock domain of the handheld object in order to correct the relative timing of environmental tracking exposures and handheld object tracking exposures.