Visual angle of the virtual viewscreen using PsychVRHMD Stereoscopic mode

Dear all,

I’m working on conducting experiments with HTC Vive, using random-dot stereograms as stimuli. Currently, I am using the Stereoscopic mode of the PsychVRHMD command to present the stereo image pair to the left and right screens. But to accurately manipulate the disparity (in arcmin) between the two eye images, the visual angle of the viewscreen (or the pixel) would be needed.
I am wondering if there is any way to extract the visual angle information of the virtual viewscreen, especially when I specify the viewing distance of the virtual viewscreen using PsychVRHMD(‘View2DParameters’, hmd, eye [, position][, size][, orientation]) command.

Thanks in advance.