Anita Lightstone (
Tamsin Lightstone (
read more fluently when the page is covered by a coloured sheet of plastic (an
overlay), or when coloured lenses are worn. Overlays provide a surface colour
whereas lenses mimic a change in the colour of a light source. In 92 patients
attending the Specific Learning Difficulties clinic at the
1. the overlay chosen from among the 10 IOO Intuitive Overlays
2. the chromaticity co-ordinates of the lenses subsequently chosen using the Intuitive Colorimeter.
There was no significant relationship between the chromaticity of the overlay and that of the lenses. In a second study, patients were given overlays to use for two months. Nineteen who derived benefit were examined using the Intuitive Colorimeter. Patients were asked to read aloud randomly ordered common words (Wilkins Rate of Reading Test):
1. with no colour
2. with the chosen overlay
3. with lenses matching the chosen overlay
4. with lenses matching the Colorimeter setting.
The aids increased reading rate significantly only in conditions (2) and (4) suggesting central mechanisms for the effects. Coloured overlays give no reliable guide to optimal lens colour.