Coloured Overlays/ Colorimetry
Visual stress (Mears-Irlen syndrome), coloured overlays and colorimetry.
Many children and adults suffer from visual discomfort when reading. Approximately 5% of the population are severely affected by Visual Stress and 20% to a lesser degree.This can affect reading fluency, concentration and comprehension and can cause rapid fatigue. This Visual Stress can cause symptoms such as movement of print, rivers running through the print and headaches/eyestrain. At Broadhurst Optometrists, we have over a decade of experience in using this system to assess both children and adults for visual stress and in providing Cerium tinted lenses where beneficial.
Visual stress is found to exist in many conditions including:
- Photosensitive Migraine
- Photosensitive Epilepsy
- Head Injuries
- Multiple Sclerosis
Colour has been found to be hugely beneficial in alleviating the symptoms caused by Visual Stress for many years. This has been confirmed by the evidence based research carried out by Clinical Psychologist Professor Arnold Wilkins and the Medical Council, the leading Government funded research body in theUK. In order to carry out this research Prof. Wilkins developed the Intuitive Colorimeter to prescribe Precision Tinted Lenses.
What is Visual Stress?
A condition contributing to reading difficulties, eye strain and headaches when reading. It can be responsible for light sensitivity, appearance of patterns in the text and glare effect.
What causes the Visual Stress?
The hypothesis is that the stress is due to a hyper excitability of the neurons in the visual cortex, an area of the brain at the back of the head, which fire inappropriately. In other words these cells kind of work a bit too fast which causes the disturbances in the text.
Is visual stress the same as Dyslexia?
Visual stress can be due to a number of conditions including Dyslexia, but is not the same. Dyslexia is a term used to describe various specific learning difficulties that affect the ability to learn to read and spell correctly. Visual Stress is NOT Dyslexia but can be particularly prevalent in Dyslexic individuals. If Visual Stress is identified and colour is used to alleviative some of the symptoms then other learning difficulties such as Dyslexia are easier to cope with.
Many people with Dyslexia may also suffer with visual stress and can therefore be helped by colour. Equally there are a large percentage of children and indeed adults who are not identified as being Dyslexic but still suffer with these symptoms. The appropriate coloured overlay or Precision Tinted Lenses can also help this group of individuals.
It is therefore important that overlays should not be reserved only for those pupils who have been “statemented” or identified as being in need of specific help. They should be available to any child who does not naturally like to look at books.
What are the signs of Visual Stress?
- rubbing eyes
- increased blink rate
- poor concentration
- using finger as marker
- low self esteem
Can adults be affected?
As people get older and text is not such a meaningless group of words, Visual Stress can be less pronounced, but still there. In a lot of cases the syndrome goes undiagnosed and untreated until adult life.
Can you have perfect eyesight and still experience visual stress?
YES, perfect eyesight means you can read all of the letters on the chart without glasses and both of your eyes work together in the way they should. Visual stress can come from a binocular anomaly, but this will be corrected before any colour is used. If Visual Stress is still occurring after all binocular problems have been sorted the cause is likely not to be due to the eyes but the visual cortex part of the brain. Colour is likely to help on these cases.
What are coloured overlays?
Sheets of transparent coloured plastic, to be placed over the required text. Used as a screening tool to determine if colour will be of benefit to each patient. They can alleviate some of the visual stress, making reading more comfortable. Each child will benefit from a different colour. To assess the benefit with the chosen colour the Wilkins Rate of Reading test can be carried out.
What if overlays are helpful?
If the child continues to use the overlay, unprompted, or the teacher/parent reports an improvement it has most likely been beneficial. The overlay is usually given as a trial period for approx. 6 weeks to rule out novelty factors. Glasses with coloured lenses can then be prescribed. These are more convenient as they can be used with board work. The tint is a much more precise tint as many more colours combinations are used. Again the tint will vary from person to person.
How can I get coloured lenses?
The colour of the lenses can only be assessed by using The Intuitive Colorimeter, which uses a much larger range of colour combinations than used with the overlay assessment. This therefore gives a much more accurate colour specific to each patient. One of our trained optometrists will conduct the assessment. When you wear glasses the whole of your visual field is coloured ie you are fully adapted to that colour. The Intuitive colorimeter takes account of this and tests in the same way so that no other colour of light is involved. Overlays on the other hand only cover part of your visual field therefore white light plays a big part. The colour of the lenses is therefore different to that of the overlays due to the colour adaptation factor
Where can I get assessed for coloured lenses?
At Broadhurst Optometrists we have been conducting coloured overlay and colorimetry assessments for over a decade with some graet success stories. Details of exactly what our assessments entail are detailed below.
What is involved in the assessment?
The appointment will usually consist of three parts.
1) An eye examination with the optometrist
The optometrist will carry out a series of tests to check for any visual or eye health problems. These tests help to rule out any other causes of symptoms such as needing spectacles, or a binocular vision (eye muscle) problem. The optometrist will also look at the eye in detail to make sure it is healthy. This part is essential even if a recent eye examination has been carried out elsewhere as it contains tests that may have not been performed as part of the standard eye examination.
2) An overlay assessment
This appointment is usually carried out by a dispensing optician. We have a range of overlays (coloured perspex sheets) to try. Each sheet is tried in turn to determine which gives the most comfortable vision. The best overlays are then used with a Wilkins rate of reading test. This is a test to measure the reading speed with and without the overlay to see if any benefit is obtained. At the end of this appointment cycloplegic drops are often instilled into the patient’s eyes, particularly in children and young adults. These drops relax the accommodation and take about thirty minutes to work.
3) A cycloplegic refraction with the optometrist (not always necessary with adults, the optometrist will advise)
After thirty minutes have passed, the patient will see the optometrist again for a short eye test to see whether there is any increased prescription with the accommodation relaxed. This is necessary as the symptoms of eyestrain and slow reading may be caused by an undetected need for spectacles. As children have a lot of natural focus they sometimes over focus during the normal eye test and therefore are found to have normal vision, when in fact they need spectacles. With the accommodation relaxed this can easily be determined and spectacles can be prescribed if necessary. The optometrist will go through the results of all the tests following discussion with the patient, or parent, the course of action can be determined.
Will I need glasses?
Following the eye test the patient may be prescribed with spectacles, or an overlay. In this case there will usually be another appointment arranged for six weeks time to see if there has been any improvement. Patients who are still getting a benefit from their overlay at this point should consider precision tinted spectacles. We also supply Chromagen contact lenses as an alternative to tinted glasses.
What are the benefits of precision tinted spectacle lenses?
An overlay can only be placed over written text. Coloured spectacles provide a tint for all tasks, such as reading the schoolboard, using a computer and writing. There is also a much larger choice of colours, so the exact specific tint may be selected. This is done using an instrument called the Intuitive Colorimeter, which allows the correct shade and intensity of colour to be chosen. Several studies have shown that the colour sometimes has to be very specific to work therefore coloured spectacles often work better than overlays.
Are there any other benefits to coloured spectacles?
Several studies have found that some individuals get a reduction in migraine frequency by wearing coloured spectacles. There is also some evidence that there may be a benefit in some epilepsy sufferers who have a visual trigger to their attacks, although this is not well understood.
If you would like an information pack, or to book an assessment, call the practice or complete our ‘quick contact’ form and we will be happy to help.