Can pulsed lighting help adults with dyslexia to read better: Testing LeFloch and Ropars’s hypothesis

Abstract The aim of the present study was to test Le Floch and Ropars’ hypothesis according to which dyslexia is mainly triggered by visual processing deficits, namely an absence of eye dominance, which induce the aberrant perception of afterimages for individual letters. According to these authors, dyslexic readers would be expected to produce reading performances very similar to those of controls under pulsed lighting conditions. 23 participants with dyslexia and 19 control readers were recruited and asked to perform two reading tasks under three different lighting conditions; standard lighting, pulsed lighting and a combination of the two. We used two reading measures for each participant and each lighting condition: (1) a reading accessibility index (using the MNREAD test) and (2) a text reading comprehension score. To control for individual differences in reading skills, all participants also completed a series of French standardized tests which were used to compute an individual reading impairment score. Finally, visual acuity and eye dominance were measured to control for participants’ visual function. We found no effect of lighting conditions on either of the two reading measures. This was true for all reading impairment score values and irrespective of whether participants showed eye dominance or not. Furthermore, even under pulsed lighting, individuals with dyslexia did not reach the reading performance of skilled adult readers, regardless of their eye dominance. In conclusion, we failed to show a clear positive impact of pulsed lighting on the reading skills of adults with dyslexia. This set of results does not support the visual hypothesis of dyslexia proposed by Le Floch and Ropars.