Vision and reading difficulties part 3: coloured filters - do they work?

This is the third article in a series of five on Vision and Reading Difficulties. The first article provided a general overview of learning disabilities and specific learning difficulties (SpLD). It outlined the role of the optometrist in helping people with SpLD. The second article covered conventional optometric correlates of reading difficulties (e.g. binocular vision problems) This article and the next will describe the use of coloured filters to treat a condition now know as "visual stress", which is often associated with reading difficulties; the symptoms of visual stress were described in Part 1. The terminology for this condition has changed over the years (e.g. Scotopic Sensitivity syndrome, Meares-Irlen syndrome). Terminology is discussed more in Part 4.