In focus: Do coloured filters rely on placebo effect?

A review paper published in this month’s Ophthalmic and Physiological Optics (Optician 09.09.16) has drawn the conclusion ‘that the use of coloured lenses or overlays to ameliorate reading difficulties cannot be endorsed and that any benefits reported by individuals in clinical settings are likely to be the result of placebo, practice or Hawthorne effects [behaviour changes caused by being observed]’.

Perceptual difficulties when reading have been cited for many years. These include reports of print blurring, doubling or moving, glare from textual patterns, and asthenopic-like symptoms of head and eye ache.

Claims that coloured filters could alleviate these were reported by a New Zealand teacher, Olive Meares, using coloured overlays and a US psychologist, Helen Irlen, using selectively coloured spectacle lenses.