​Visual difficulties

Some people experience visual discomfort or disturbance when they read. Common symptoms that may significantly impair reading ability, or make reading very tiring, include:

• headaches and eyestrain associated with reading and/or other near work
• text appearing blurred or going in and out of focus
• text appearing double or alternating between single and double
• difficulty keeping place in text
• difficulty tracking across lines of text
• discomfort with brightness of the page or contrast between text and background
• text that appears to shimmer or flicker

Symptoms such as these have a variety of different causes, some of which may be due to disease or abnormality, so they must be investigated by a professional who is qualified to diagnose them correctly and give appropriate treatment. Anyone who experiences such difficulties associated with reading should consult a registered optometrist for a full assessment of eye health and visual function.

While adults may recognise symptoms, children may not be aware of them, as this is how they always experience reading. For this reason, any child who is a struggling reader should be assessed by an optometrist to either rule out or treat visual difficulties. This assessment and treatment is to check the health of the eyes and to enable clear and comfortable vision; treatment of visual difficulties is not treatment of dyslexia.

All children under the age of 16, and young adults under the age of 19 who are in full-time education, are entitled to a free NHS sight test with an optometrist, and to an optical voucher to help with the cost of glasses or contact lenses. The NHS sight test is sufficiently comprehensive to enable the optometrist to assess eye health and identify the likely causes of visual problems that affect reading and other near work. This should include an assessment of the ability of the eyes to focus and work together correctly (binocular accommodation and convergence).

In many cases the NHS sight test is all that is required to enable an optometrist to identify a problem and provide appropriate treatment with prescription glasses or contact lenses. Sometimes, however, the optometrist will consider that further assessment and/or other forms of treatment are necessary. The most likely of these will involve full assessment of binocular vision which may need treatment with eye muscle exercises (known as orthoptics or vision therapy) and/or pattern-related visual stress which may sometimes be alleviated using precision-coloured overlays or lenses. Such assessments and treatments are outside the scope of the NHS sight test, so the optometrist will either offer these privately for a fee or refer to another practitioner, such as an optometrist working in a specialist university clinic, or an orthoptist working in NHS secondary care (hospital). All NHS hospital orthoptics departments and university specialist optometry clinics will undertake assessment and treatment of binocular vision anomalies, but not all will offer assessment and treatment of visual stress.

The vision screening that most children undergo at school entry (age 4 to 5) is only a test of whether a child can see clearly in the distance. It is not a comprehensive assessment of eyes or vision and does not test any of the functions required for clear and comfortable vision when reading. For this reason, every child should have a full sight test when they start school, and as frequently as recommended by their optometrist after that.

Some websites and providers of education resources offer coloured overlays, tinted reading rulers, and other devices that may make reading easier and more comfortable for some children. These aids may be helpful, but it is very important that these aids should not replace or discourage full professional assessment. In particular, coloured overlays and similar aids must not be promoted as the first strategy to help children with reading difficulties. If children have visual difficulties, then it is essential that these are diagnosed and managed correctly by qualified, registered professionals.

For information on how to make written text dyslexia friendly see the BDA's Dyslexia Style Guide.