[1] Univ Ulster, Vis Sci Res Grp, Coleraine BT52 1SA, Londonderry, North Ireland
[2] Royal Victoria Hosp, Orthopt Dept, Belfast Hlth & Social Care Trust, Belfast BT12 6BA, Antrim, North Ireland
[3] Univ Ulster, Sch Psychol, Coleraine BT52 1SA, Londonderry, North Ireland
[4] Northern Hlth & Social Care Trust, Dept Paediat, Belfast BT41 2RL, Antrim, North Ireland