Visual stress is a broad term that refers to a condition that occurs in a wide range of neurological disorders. It is a scientifically confirmed neurological condition thought to affect about 20 percent of the population. Visual stress is characterized by hyperactivity of the brain’s visual cortex, preventing this area of the brain from processing visual information correctly.
Patterns of light like flickering lights or strobe effects can also trigger visual stress, resulting in visual and perceptual distortions which can affect the way a person sees when they look at a repeating pattern such as stripes or lines of text. Other distortions include illusions of colour around letters or around the page, doubling of print and washed-out areas of print. Such distortions can also affect how a person feels.
Here’s how coloured filters can help to ease visual stress.
Identifying Visual Stress
In the 1980s, Maeres and Irlen each described a cluster of symptoms that affected reading. Investigators and researchers have since defined the cluster of symptoms that affect reading to include print distortion, eye strain and headaches.
Other names for visual stress include:
- Irlen Syndrome
- Maeres-Irlen Syndrom
- Perceptual Dyslexia
- Visual Dyslexia
- Pattern Related Visual Stress
Treating Visual Stress
Using coloured filters and coloured paper to ease eye strain while reading has been employed for decades. This initial approach was developed by Helen Irlen but her method has been questioned due to a lack of scientific evidence surrounding the diagnostic process.
Although they require additional research, newer systems using the Intuitive Colorimeter, are gaining acceptance in the optometric community. However, when reviewing the published literature on the condition and treatment, there are confusing factors, namely:
- Selection of participants
- Definition of visual stress or similar condition
- Corrections for other visual factors such as binocular instability
- Inability to mask the filter to the subjects and more
Coloured overlays are sheets of coloured plastic film suitable for placing over a page of text when reading and have been shown to reduce visual stress and increase reading speed. The increase in reading speed happens only when a sufficient number of colours are available to choose from, as the optimum colour needed differs from person to person.
Coloured glasses have been shown to reduce headaches in trials. The optimal colour for overlays differs from the optimal colour used in lenses.
Balance of Evidence
Conditions such as refractive error and binocular function should be dealt with before coloured filters are considered as an option for people experiencing visual stress.
In spite of the limitations of the research, the balance of evidence suggests that coloured filters can alleviate symptoms or improve performance in people who suffer from visual stress.
