Our research base and other questions

What is the theory behind our Visual Stress Products?

Our overlays and reading rulers were developed according to the research done by Bruce Evans, of the Institute of Ophthalmic Opticians and Arnold Wilkins of Essex University.     Their research is now supported by many other peer reviewed papers.   (See link to Prof. Wilkins’s site below.     Arnold Wilkins now has 184 peer reviewed papers on his site at Essex University and has received several prestigious awards for his work on defining Visual Stress and pattern glare. 

We follow Arnold’s research to determine the correct amount of colours to cover the spectrum of hues at a defined depth and saturation.  This includes colours that are not often used but are needed to ensure that when testing no student is missed.    

Why do we claim that our rulers and overlays are among the best on the market?   

All our reading rulers and overlays are made using eco-friendly PET.    This is one of the most ultra clear plastics available and it provides a smoother substrate for colour printing than commonly used PVC.    Cerium use an acrylic substrate which is also very clear.     Most of the overlays on Amazon as we write are PVC, which has less clarity, a slight yellow tint and an uneven surface making it impossible to guarantee the end colour batch on batch. 

Our colour integrity:     Our first small batches of visual stress products were quite variable in different batches because of the printing process.     However as the popularity of the overlays grew we were able to change to a bigger company who had state of the art printing presses costing well over $3 million each.     These printing presses can be adjusted every inch of a sheet to ensure colour consistency.       In an adjoining factory our suppliers actually manufacture from oil the PET they use for us, which they produce with a priority on clarity and strength of scratch resistance.    They work on this spec to improve it with each batch.      Every batch is checked on production to have a variance from the original colour sample (created from Professor Wilkins’s research statistics) of no more than Delta 3.  Most, if not all, are below Delta 2, and some are under Delta 1.

Where do our products stand with the BDA (British Dyslexia Association)?

Our latest batch of page overlays and reading rulers and some of our marketing statements carry the “BDA Assured” badge. BDA Assured was a programme run by the BDA from 2019-2021 which gave the “BDA Assured” badge to resources that were recognised by the BDA as being helpful to people with dyslexia.  During that time, Crossbow reading rulers and coloured overlays were part of the scheme.  This programme has now been discontinued, and will be replaced early in 2022 by a new page of useful resources.

Climate and sustainability considerations:

We consider our responsibilities to the earth we live on in the development of every new product we make.    All our exercise books are printed on Carbon Capture paper and printed in the UK by a company with a Green Achiever Certificate.       We do not use PVC in our overlays and reading rulers: we only use recyclable PET. All the production processes, from the oil received to the final printing on the clear PET sheets is done by the same company and properly audited to continually improve sustainability.  

The directors of Crossbow Education Ltd have personally visited the factory on three separate occasions, and we have seen for ourselves that employee working conditions are good.   

Crossbow and Other bodies of Peer reviewed research:
As is the case with most bodies of scientific research, there are peer reviewed studies on visual stress and coloured overlays that contradict each other.     We enjoy keeping an eye on the development of new angles of research.    We follow well-documented peer-reviewed research and will adapt as it becomes clear what is the best practice. 

This leads us to the SASC report in 2018
that advised against using a system that did not advise check ups with an optometrist as a normal rule.    In order to make this clear they advised teachers to just do the pattern glare test then send children to an optometrist for colour testing.    This meant The Assessment Pack was also not advised as a rule of thumb.  However later in the report it was acknowledged there might be a place for testing using the Assessment Pack.

It obviously makes a lot of sense to emphasise the importance of a medical professional making the final diagnosis.       However much of what was discussed on a suitable path to getting this professional diagnosis was in the form of suggestions only, and there are many instances where it would not be possible to implement them immediately, if at all.    As the report says there is much to be thought out before a cohesive pupil path is set out.    The report was 34 pages long so we cannot summarize it here, but we will talk briefly about the  aspects that particularly concern The Assessment Pack.    

1.     In the SASC report, Travers 2017 is quoted as saying that it is important to follow a conservative path of risk for children, ie take as safe a path as possible.  However there is much discussion as what the safest path is, and whether all children will even know there is a specific problem without seeing the difference colour makes.    The pattern glare test is not available in all schools.   Even if children do a pattern glare test and are referred for colour testing,  it can be a problem to find an optometrist who specialises in colour.     Optometrists are not obliged to test for visual stress.     It is not an eye problem, so much as a problem with the way the brain reacts to pattern glare.   “Vision and Reading Difficulties” (Allen, Evan, Wilkins, 2010) suggests that only about 30% of difficulties affecting reading are disorders of the eye (such as Binocular instability) and  these are not covered in the standard eye test.     If someone goes for a test after being referred to an optometrist, there is a likelihood that they forget the specific wording and just ask for an eye test.   This is a taste of many problems in actually implementing a report like this.     We would like to ask if the optometrist is even the right professional to go to if the problem is in the brain: for example, would an optometrist testing the eye find any evidence of a brain tumour?     Or if there are other brain problem like depression or sleeplessness, would a GP be better?    We at Crossbow are interested and are willing to adapt and change the method of testing in the assessment pack, but will not rush into the implementation suggested in one report, that as yet shows only a little actual practical evidence that using just the pattern glare test is in fact the safest practise to impose on UK teachers.   

2.    It has been suggested that too many teachers jumped straight to the conclusion that if colour helped it was Visual Stress.    We have discussed this with other professionals and believe we could help here.  We could change the wording in some places to say ‘Visual Difficulties’ rather than Visual Stress, so that the top thought assessors come away with is ‘Visual Difficulties’.        The revised book will be available in February 2022.     The functionality of the book will remain the same.   We will also change the name,  probably to ‘The Colour Assessment Pack.

A Bit of Background History on visual stress:  

Research into how colour helps was originally done by Olive Meares and Helen Irlen in the early 1980s, working independently and unknown to each other in different parts of the world.     Helen Irlen in California went on to trialling tinted lenses and set up Irlen® centres initially in America but now all over the world.  She called the condition “Irlen® syndrome.”  Her work did not lead her to work with mainstream optometrists.     She preferred to use her special practitioners and only the colours the Irlen® centres decided on.   We follow a different process and use different hues in seeking to address the needs of people with visual stress. Crossbow do not have practitioners providing tinted lenses.  

Professor Wilkins describes how he became interested in what he now calls visual stress in his book Reading Through Colour (Wiley 2003).     He was at the time a professor at Cambridge University and as a scientist with the Medical Research Council he had spent 10 years researching photosensitive epilepsy.    During this time he used electrodes to measure the electrical activity of the brain in people presenting with photosensitive epilepsy.     This led to the discovery that there were geometric patterns with very specific characteristics that enhanced the risk of a seizure.   He then noticed that some friends and colleagues commented that they would get headaches if they looked too long at the patterns he was using.    He conducted further experiments on these people and then others who said they got headaches from reading.   Noting results and varying the patterns.     He describes the process in “Reading Through Colour.    He records how in 1985 he found an article about colours and helping children to read and built an instrument to test children.      This developed later into the colorimeter now used in many optometrists’ practices.      

While Arnold was developing his theory of Visual Stress The Irlen® institute was developing the Irlen® centres.     However they did not end up moving in the same direction.     Irlen concentrated on setting up the Irlen® centres to help children in mostly educational environments.     Arnold Wilkins started to work with Optometrists and became very involved in establishing a scientific validation of the principals behind the Colorimeter.

How did Crossbow Education get involved with visual stress?

Crossbow was founded in 1993 by SEN teacher Bob Hext  to produce multisensory resources to help with reading and spelling, based on his own work with dyslexic children.  In 2004, a teacher in America sent him a  yellow – edged plastic strip that she said worked to help children track when reading.     We found this to be very helpful for tracking as it highlighted just one line in yellow or blue so children found it easy to keep their place. The transparent tints also seemed to make the words clearer for some children.  Anne Hext contacted Mark College, a beacon dyslexia school in Somerset, and asked them to look at some designs she had done to develop something in the UK that would help with clarity and tracking.    They said it would be much more useful if it had the possibility of using it to read a paragraph at a time as well as a single line.      Anne and Bob worked on a suitable design and had them made. A patent was granted for their design, which they called the “Eye Level Reading Ruler.”

By this time Arnold and the Optometrists he worked with had started to publish peer to peer validated research on reading through colour.     Anne and Bob met Arnold and have followed his research ever since, and he has advised us on colours and shapes. He is not too keen on the small reading ruler as the bigger A4 overlay does a more comprehensive  job at screening out the high contrast pattern glare.      However, children find the reading ruler is less intrusive and  more often have the courage to use it  in the classroom.    Peer-reviewed research in 2019 has shown that the use of a reading ruler increased reading speed by  an average of 20% (as opposed to 22% with the larger overlays).

Where does Crossbow fit in the pupil path?

Our process is to inform people about visual stress and other visual difficulties and help them egonomically,  both in schools and workplaces.   We advise the teachers or assessors to actively encourage students and people who find they are helped by colour that the next step is to go and see an optometrist and explain that we only test for which colours might be helpful;  we cannot test for what underlying condition is causing the problem.    

We believe that just as the first discovery of colours helping people read was made by actually putting a colour on a page, the same is true today.   Many people who are up to date with their optometrist tests come to us and discover they are really helped by reading with colours. They often don’t realise there may be a visual difficulty: they just assume they are being “thick” or “slow” until they see the difference a specific colour can make.      We direct them back to an optometrist to re-check for general eye health.   Sometimes they take a reading ruler to the optometrist and if the optometrist specialises in Visual Stress they will take further action as the patient requires.    Some pupils go on to have tinted lenses and we have photocopiable leaflets in the Assessment Pack  to give out, telling people where and how to find an optometrist and what could be available.     We have an opticians list on our website  (we are currently working to improve it, so it may be down at the moment) giving the various qualifications and specialisms each one offers.    

 What is Visual Stress and Why don’t all optometrists test for it?

Visual Stress is at present the name Arnold Wilkins suggested for the over-reaction that can be recorded in the brain,  not the eye,  when looking at certain repetitive geometric patterns.    Text at certain sizes has been shown to trigger this over-reaction in some people, thus causing the text to appear to float, or move or blur.    The optometrist is of course testing the eyes, so this would not be apparent from a standard NHS eye test.   Children going in with reading rulers and overlays has prompted some optometrists to take an interest and add this specialism to their offering.   Some had seen ‘the colorimeter’ and lately ‘the curve’ and looked at testing visual stress from seeing these instruments.   It remains entirely the optometrists’ choice whether or not they go into testing for a brain problem like visual stress.   

Why do we not just advise testing for pattern glare?

Many people we ask, including teachers, have never heard of a pattern glare test.   Similarly, unless the problem is so severe that the teacher is actively needing to find out what is wrong, the child will not even realise there is a problem and will not go forward for a pattern glare test even if it is offered.    On the other hand, the reading ruler is used extensively  in classrooms, giving some children the opportunity to read more easily and start on the path to uncover whatever it is causing the visual difficulty.