Piano Technique: When scale notes go off the radar screen

One of my Skype students is practicing the D Major scale in contrary motion. (Her thumbs at Middle D) We start slow triplets to 16ths, to 32nds (Legato/Staccato/Forte/piano) The snag occurs at the third and final octave out, where most students think the notes are off the radar--but in truth peripheral vision and/or rolling eyeballs…