“…The C12 had a 12" screen with an optimal working distance of 23.5" (60 cm) between eyes and screen, and the P10 had a 15" screen with an optimal distance of 20-28" (50-71 cm). Involuntary head movements had to be 1 (Copley & Ziviani, 2004;Brodin & Lindstrand, 2003;Hasselbring & Glaser, 2000) 2 (Hemmingsson, Lidström & Nygård, 2009;Hoppestad, 2007;Martin, Martin, Stumbo & Morrill, 2010) 3 (Copley & Ziviani, 2004;Hoppestad, 2007;Rose, Hasselbring, Stahl & Zabala, 2005) 4 Dettmer, Dyck & Thurston, 2002;Villeneuve, 2009;Hemmingsson, Gustavsson & Townsend, 2007) 5 (Brodin & Lindstrand, 2003;Lenker, Fuhrer, Jutai, Demers, Scherer & DeRuyter, 2010) 6 (Baxter, Enderby, Evans & Judge, 2012;Granlund, Björck-Åkesson, Wilder & Ylvén, 2008) taken into account in individuals with cerebral palsy, so devices for eye gaze control needed to allow for head movements (Donegan, 2012). The C12 and P10 devices allowed for the following range of head movements: 15.7x11.8x7.9 in (C12) and 12x6x8 in (P10).…”