People with specific learning difficulties have problems with certain skills at school. The most common type of specific learning difficulty is specific reading difficulty; and this is often called dyslexia. Dyslexic children are usually poor at spelling and may seem intelligent in conversation, but have trouble with written language. If a person is dyslexic then it does not mean that they are unintelligent: Leonardo da Vinci and Einstein are both thought to have been dyslexic.
Dyslexia is best diagnosed by an educational psychologist or specialist teacher who, in addition to other tests, may calculate a person's expected reading age from their intelligence and age. The difference between this and the actual reading age, as measured with a reading test, gives a measure of the reading difficulty. The term dyslexia is usually reserved for a severe degree of reading difficulty and testing for dyslexia is discussed below. It is important to stress that dyslexia is not a visual problem, though it can be linked to some visual problems as explained below.
The term dyslexia is used throughout this document, but the visual problems that are described can also be present in children who have other, non-dyslexic, difficulties at school. A person does not have to be diagnosed as dyslexic in order to benefit from the tests outlined here. Visual problems can also co-occur with other specific learning difficulties, such as dyspraxia (co-ordination difficulties) and dyscalculia (difficulty with maths). Optometrists do not test for or diagnose dyslexia or these other learning problems and testing for these conditions is discussed in more detail at the end of this page.
Most experts agree that problems with sight are not a main cause of dyslexia. Certain visual problems, however, may occur more often in dyslexia and these may add to the burden when trying to read. These visual problems may not be detected in a standard eye test. One of the most common visual anomalies in dyslexia is poor or unstable co-ordination of the two eyes (binocular instability). This can cause eyestrain, visual distortions, or headaches and may slow reading and discourage children from prolonged reading.
It should be stressed that most people with dyslexia do not have visual problems, but some have visual anomalies without realising it. People with a mild specific learning difficulty, perhaps not bad enough to be called dyslexia, can also have these visual problems. These problems might cause difficulties in perceiving the correct order of numbers as well as letters on the page. For some people, this might contribute to difficulties with mathematics. Binocular instability can usually be treated with simple eye exercises. In some cases, glasses may be prescribed.
An eye examination with an optometrist will not be able to diagnose dyslexia. But if dyslexia is suspected then it is sensible to investigate whether there are any visual difficulties that may be making school work more challenging.
Our principal optometrist, Professor Bruce Evans, was described (in a review of his book, Dyslexia and Vision) as “the UK’s foremost expert in the area of visual correlates of dyslexia”. This was the subject of Professor Evans’ doctorate and he frequently lectures on this topic, in the UK and in many countries. His research has been published widely, including a book for teachers, psychologists, and parents called Dyslexia and Vision. For more information on (or to buy) this book, click on Dyslexia and Vision and search for Dyslexia and Vision. He has also co-authored a book on Vision and Reading Difficulties which has become a respected textbook for eyecare practitioners on this topic.
Professor Evans is reducing his days at the practice and he has trained three colleagues at the practice, Dr Claire O’Leary, Mrs Anita Shah, and Ms Ella Wyss to take over the new referrals of patients with reading difficulties, migraine, and epilepsy.
These practitioners see patients at the practice to carry out a full eye examination and additional tests to look for the visual problems that may be associated with difficulties at school. These appointments usually take about 1 hour and the fees are detailed on the Eyecare page of this website.
These fees include a report explaining the investigations, results, and recommendations. Many tests are necessary at the first examination but it is not usually appropriate to repeat all of these at subsequent consultations.
If you would like to arrange an appointment with one of our specialists, please telephone our reception and ask for a special investigation for the assessment of visual problems that may affect performance at school. When the appointment is arranged, we will send you written confirmation, a map directing you to the practice, and a questionnaire. It is very helpful if you can complete the questionnaire and bring it with you to the appointment. If would like another copy of the questionnaire then it can be downloaded by clicking: specific learning difficulties questionnaire.
Some people with difficulties at school report a benefit from using coloured filters. This is a controversial topic and it is widely agreed that coloured filters should not be thought of as a treatment for dyslexia. Recent research indicates that about one in five people with dyslexia may also have a co-occurring condition that causes them to experience visual distortions (e.g., words appear to move or blur) and/or eyestrain and headaches from a page of text. Some of these people report a reduction in their symptoms with coloured filters and this condition has been called Visual Stress (also known as Meares-Irlen Syndrome, Irlen Syndrome, or Scotopic Sensitivity Syndrome). If our findings indicate that a person may benefit from colour then we may invite them to try using a coloured overlay when reading.
Many teachers also test children with coloured overlays and these can be bought inexpensively on the internet. For those using iPads or iPhones with iOS 10 or later there is a very good free way of investigating whether coloured filters may improve the perception of text (illustrated above). Instructions on how to use this, and other software (e.g., for Windows computers) can be found at Colour modifications for display screens, which also provides other approaches to reducing the symptoms of visual stress.
If coloured overlays or a coloured background on a screen are found to be helpful and the person is happy to wear coloured glasses when studying then a further appointment can be arranged for testing with a special instrument, the Intuitive Colorimeter (illustrated below). This enables the precise tint for glasses to be determined. The charge for this further investigation is detailed on the Eyecare page of this website. We believe that it is important to only prescribe coloured glasses for children who really need them. When children report an initial benefit from coloured filters or a coloured background this could be because of novelty or placebo effects. Therefore we ask for a trial of at least 3 months with coloured overlays or a coloured background so that the child, parents, and teachers can determine whether there is a sustained and significant improvement before deciding to return to be tested for coloured glasses.
For patients who are prescribed Precision Tinted lenses the exact colour of tint that is required can, like any other optometric prescription, change over time. Therefore, we usually repeat the testing with the intuitive colorimeter at yearly intervals. This is typically only necessary for children as with adults the tint only very rarely changes.
As explained above, visual problems are not a major cause of reading difficulties and most children we examine are given the “all clear”. In some cases, we find a visual problem that may be contributing to a child’s difficulty in the classroom because the problem deters them from reading (e.g., if reading causes eyestrain or headaches) or because it interferes with the perception of text (e.g., if words blur or move). In most cases, parents can identify these symptoms simply by going through the relevant sections of our questionnaire with their child. There are two limitations of this approach. First, in asking the questions there is an element of suggesting a problem. Some children may say “yes” for this reason or because they think that they ought to have a problem. This is especially likely with younger children. For this reason, lots of “yes” replies on a questionnaire do not necessarily mean that a child has a visual problem. However, if a child is reporting many symptoms then it is sensible to have a special investigation to see if any visual problems are present.
The second limitation of relying on children’s reports is that occasionally a child may not recognise symptoms until they are alleviated. As an analogy, optometrists sometimes experience cases of short-sightedness when a child does not report their vision as being blurred until glasses are tried that eliminates the blur. Whilst this is not uncommon with short-sightedness it is probably less likely to occur with visual stress. This is because with visual stress isolated letters or words typically appear normal and crowded text looks normal to begin with, but then starts to move and blur as the child views it for longer. This is usually identified by our questionnaire.
If, on completing our questionnaire, your child has no symptoms (e.g., words don’t blur or move and eyestrain or headaches are not frequently experienced) then it is unlikely that a special investigation appointment would identify any problems requiring treatment. In such cases, routine eye examinations may be all that is required. However, if you would like to be absolutely sure then we will still be happy to see your child for a special investigation.
Children who struggle at school with reading and spelling may have dyslexia; if they struggle with maths they may have dyscalculia; and if they struggle with co-ordination they may have dyspraxia. Any of these problems can co-exist with a visual problem. In such cases, treatment of the visual problem will help the visual component of the child’s difficulties but should not be expected to address other factors, such as dyslexia. Dyslexia is the commonest specific learning difficulty and the main cause of dyslexia is known to be a deficit of phonological skills. This is a problem with the ability to process the sound structure of words and is not a problem with vision.
If children struggle at school, then ideally, they should have an eye examination with an optometrist who has specialised in vision and learning to rule out visual factors that may co-occur with the dyslexia. However, the child should also be assessed by an educational psychologist or special needs teacher who can carry out educational tests to detect other problems (e.g., dyslexia). Your child’s school may be able to arrange for this educational testing, but most schools only have a budget to fund this testing for severe cases. Specialist assessments can also be arranged privately.
The British Dyslexia Association (BDA) is a support group which can give information on the legal situation concerning learning difficulties and legislation on education. Their helpline number is 0333 405 4567, firstname.lastname@example.org
BDA also have local associations around the country who can provide information on services in your area and provide support for families dealing with dyslexia. The BDA website is www.bdadyslexia.org.uk.
updated November 2021