Irlen lenses: a critical appraisal

The purpose of this paper is to assess the credibility of the Irlen lenses, Irlen's hypotheses, and the scotopic sensitivity syndrome. The analysis includes a review of 13 pro and con research papers. Of special interest is the dichotomy which developed between researchers who were Irlen participants and the professional and scientific community who required less disputable evidence. Even the former, however, failed to find scientific support for Irlen's concept of dysfunction in the discharge rate of the retinal receptor cells. Furthermore, in the absence of any evidence that it is a separate and distinct entity, it appears that the scotopic sensitivity syndrome is, in fact, a symptom complex which results primarily from various refractive, binocular, and accommodative disorders. Some of the papers which support Irlen's hypotheses provide reason to believe that there is a strong placebo effect.