What is the Difference Between Dyslexia and Irlen Syndrome?

February 27, 2023

You’re in class, staring at the test your teacher just handed out. But something’s wrong – you can’t understand the words. You know they’re supposed to mean sounds, but you have no idea which sounds.

And as you keep staring at them, things get worse. The bright white of the page strains your eyes. You feel a migraine coming on. The words move around, shaking, reversing, fading away.

You know something’s wrong, but here’s the question that could save your life: is this dyslexia, Irlen Syndrome, or both?

What is Dyslexia?

Dyslexia refers to a cluster of symptoms forming a language-based learning disorder that causes great difficulty reading, spelling, and recognizing words. It affects an estimated 5% to 11% of the population.

What is Irlen Syndrome?

Irlen Syndrome (also known as Meares-Irlen Syndrome, Scotopic Sensitivity Syndrome, or simply visual stress) is a perceptual processing disorder that increases an individual’s sensitivity to light. It may affect up to 14% of the population.

Irlen syndrome was discovered relatively recently, first identified by New Zealand teacher Olive Meares and American psychologist Helen Irlen in the 1980s.

Key symptoms of Irlen Syndrome include:

Headaches/migraines in bright light (including fluorescent light and sunlight).
Eye pain/watering.
Attention difficulties.
Fatigue when reading.
Poor depth perception.
Visual distortions.

For most, these symptoms are worsened when reading; black text on a white background is especially difficult for someone with Irlen Syndrome, the white glare being particularly uncomfortable. This means that reading is where most with Irlen first become aware of their disorder, and, as a result, mistake it for dyslexia. Not only does this keep them from receiving the proper treatment, but it also keeps them from being aware of how Irlen affects the rest of their lives.

To informally screen yourself for both conditions, please try our brief tests for dyslexia and Irlen Syndrome. But to learn how to tell the two apart so you can better help yourself and others affected, keep reading.

What are the Similarities Between Irlen Syndrome and Dyslexia?

In both dyslexia and Irlen Syndrome, an individual will experience some similar symptoms when reading, such as fatigue, attention trouble, and headaches. Research also suggests Irlen Syndrome is commonly comorbid with dyslexia (as well as autism, ADHD, and brain trauma). This comorbidity and symptomatic overlap has caused some to use both terms synonymously, leading to a regular misdiagnosis of Irlen Syndrome as dyslexia.

Importantly, neither dyslexia nor Irlen Syndrome are exactly visual problems. Rather, both are differences in the way the brain processes language and visual cues, respectively. Both appear to have a genetic cause, though not exclusively, and both are spectrum disorders with symptoms ranging from mild to severe.

Image by Andrea Piacquadio, Pexels

Each requires structured and early intervention to ensure that neither affect a person’s life too deeply. Because both conditions are stigmatised and popularly misunderstood, children with Irlen or dyslexia are often dubbed ‘difficult’, ‘lazy’, or even ‘unintelligent’. This means that with enough neglect, Irlen and dyslexia can lead to illiteracy, devastating your chances of social mobility.

What are the Differences Between Irlen Syndrome and Dyslexia?

While there is some overlap and conflation between the two, it is necessary to remember that they are distinct conditions.

Irlen Syndrome appears to be caused by an interruption between the synaptic path from the eyes to the brain. Dyslexia, on the other hand, disrupts communication between pathways connecting the auditory, visual, and language centres in the brain. So while dyslexia is purely a problem of phonetic/language processing, Irlen syndrome is a problem of perception processing. Or in other words, dyslexia means you don’t have the key to the code; Irlen Syndrome means you can’t see the code properly.

Most with Irlen Syndrome can process words perfectly well, but find themselves lacking concentration, losing their place on the page, developing headaches or becoming quickly fatigued, and having visual distortions when reading. In contrast, a dyslexic might experience some of these symptoms, but they’ll stem from significant trouble decoding written words into the appropriate sounds.

Dyslexia does not cause visual disturbances to the same extent as Irlen Syndrome. Just a few common visual distortions include:

Fuzzy text.
Letters moving on the page.
Words being reversed – back to front or upside down.
A ‘halo effect’, with words doubling over themselves or being surrounded by an outline.
A ‘whirlpool effect’, the words swirling in your peripheral vision.
A ‘washout’, where the white background bleeds into the black text.

Irlen Syndrome stretches across your life. The impaired depth perception caused by Irlen can affect driving, sports performance, balance, etc.

And perhaps the most important difference between the two is in treatment. A dyslexic needs a multisensory approach that helps their brains forge neural pathways connecting the symbol to the sound. This often means phonics intervention involving breaking letters into individual sounds and physically drawing these out or rearranging them on cards, for example.

The main treatment for Irlen Syndrome is much simpler. Dr. Helen Irlen discovered that processing can be made much easier by changing the colour of a text background using visual overlays. Each individual would choose from one of ten overlay colours tints that helps them best – purple, yellow, aqua, rose, etc. For somebody with severe Irlen syndrome, tinted glasses can also aid day-to-day functioning (though the tint of your glasses would differ from that of your overlay).

Image by Skitterphoto, Pexels

Can you have Both Irlen Syndrome and Dyslexia?

While both are entirely separate conditions, research suggests that dyslexics have a 50% chance of also having Irlen Syndrome (though this number may not be exact, as both have been historically conflated).

If you have both dyslexia and Irlen, not only will you have severe difficulty decoding words phonetically, but you’ll experience constant visual distortions and migraines when trying to – written language will seem virtually incomprehensible.

If left untreated, both conditions can make reading a nightmare, even leading to illiteracy. Reading is absolutely necessary to navigate our world; job applications, important emails, whole career paths, even restaurant menus and train timetables require you to read. As a result, illiteracy can isolate you socially and paralyse you professionally, putting you at much higher risk of poverty.

It is important to know if you have either Irlen or dyslexia, or both, as they require different interventions. Treating dyslexia will not cure Irlen Syndrome, and vice versa, though it may make treating the other easier.