The participant will attend a further appointment at the two week time point, and if the overlay was beneficial, an addition test will be carried out using the Intuitive Colorimeter, to determine the exact hue, saturation and intensity of coloured lenses that offer the most relief from difficulty or discomfort while reading. Once this colour has been determined, the hue will be modified to find the closest colour at which the participant first loses benefit (the point at which the discomfort or difficulty returns). Each colour setting (beneficial and non-beneficial) will be noted and the participant will be provided with spectacle lenses tinted exactly to one of these colour specifications. In a crossover design, the order in which true or control lenses will be provided to each participant will be determined by random number generation. Allocation will be carried out by personnel who are not researchers on this study, and who know the order (true lens tint first or second) as 1 and 2. Ordering of tinted spectacles will be handled by the personnel who are not researchers on the study, and this information will not be accessible by the researchers. Thus, tinted lens ordering will not be shared with the researchers, who will not know whether each participant is wearing the beneficial or non-beneficial tint, and so will be masked. Similarly, participants will be unaware whether they are wearing the true or control tint, at any time during their participation. The non-beneficial tint will be very similar to the beneficial tint, so neither researchers nor participants will be able to determine this. On this occasion the participant will also be asked to describe the difficulties he/she has experiences when reading with and without the coloured overlay.