Each eligible participant who agrees to take part in the study will undergo testing with coloured overlays, to determine whether a particular overlay appears to be beneficial in terms of reducing difficulty or discomfort while reading. If so, the participant will be provided with the overlay to use for a period of two weeks, to determine whether it is consistently beneficial when reading during that period. In addition, the Wilkins Rate of Reading Test (WRRT) will be carried out at this baseline stage with and without the overlay.