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Investigating the Possible Overlap Between Dyslexia and Irlen Syndrome

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by Mag. Nina Čelešnik, teacher in Elementary school in Ljubljana, Slovenia, and certified Irlen Screener
Email correspondence to celesniknina@gmail.com

 

Abstract

While dyslexia has long been recognized in Slovenia, Irlen syndrome only began to receive attention in 2015. Due to overlapping symptoms, these two conditions are often mistakenly conflated by both professionals and the general public. This misunderstanding can have significant consequences, including the mislabeling of individuals as lazy, incompetent, or unintelligent, and more critically, the denial of appropriate interventions. Through a review of existing literature, we aim to delineate dyslexia and Irlen syndrome as distinct conditions requiring separate diagnostic and treatment approaches. We present a comparative table that outlines the unique and overlapping characteristics of each condition and propose an evidence-based sequence of interventions for individuals, particularly children, presenting with reading-related difficulties.

Keywords: Irlen syndrome, dyslexia, visual processing, reading difficulties, diagnostic protocol

 

Introduction

Dyslexia is a well-documented condition in Slovenia, whereas Irlen syndrome was only formally recognized in 2015. The symptom overlap between the two disorders frequently leads to the incorrect assumption that they are identical. However, this is a misconception. Such confusion may result in individuals being unfairly labeled as unmotivated or lacking intelligence, and more importantly, it may prevent them from receiving appropriate and effective support.

This paper outlines the similarities and differences between dyslexia and Irlen syndrome, and emphasizes the necessity of distinguishing between the two in both diagnosis and intervention.

 

Overview of Irlen Syndrome

Irlen syndrome, often confused with dyslexia due to shared symptoms affecting reading, is a distinct condition with a neurological basis. Dyslexia is primarily a language-processing disorder, typically characterized by phonemic awareness deficits and associated with underactivity in the left temporal lobe. Irlen syndrome, by contrast, is a visual processing disorder resulting from hyperactivity in the visual cortex. This difference in underlying cause leads to distinct symptom profiles.

Irlen syndrome is a sensory regulation disorder marked by difficulties in processing visual stimuli, often exacerbated by sensitivity to specific wavelengths of light. This can lead to symptoms such as visual distortions (e.g., letters appearing to move or fade), headaches, nausea, and fatigue.1-3 These symptoms can impair concentration and reading fluency, potentially affecting academic performance and emotional well-being.

When individuals with Irlen syndrome engage in visually intensive tasks, such as reading, listening, or sports, the brain is subjected to heightened visual stress. This results in a range of physical and cognitive symptoms, including eye strain, sleepiness, and poor reading comprehension. Long-term consequences may include increased restlessness, reduced self-confidence, and elevated stress levels.4, 5

Custom-tinted lenses tailored to an individual’s specific needs can significantly alleviate these symptoms and contribute to improved overall functioning. Positive outcomes have been observed in areas such as anxiety, sleep regulation, interpersonal relationships, and self-esteem.1, 5-6

 

Overview of Dyslexia

Dyslexia is a neurodevelopmental disorder that manifests as difficulty acquiring reading skills despite adequate instruction, intelligence, and socio-cultural opportunity.7  It is the most prevalent learning difficulty, affecting approximately 80% of individuals with learning disabilities.

Studies indicate a significant overlap between dyslexia and Irlen syndrome: Irlen reports that 33% of individuals with dyslexia also present with Irlen syndrome,1 while others place this figure at 41%.8 Given dyslexia’s pervasive impact on academic performance, especially in reading and language-based tasks, early recognition and multidisciplinary intervention are crucial.

Wajuihian and Naidoo emphasize the vital role of optometrists as frontline professionals in identifying reading difficulties, advocating for their inclusion in multidisciplinary teams.7 Slovenian educational guidelines (2018) further describe dyslexia as a neurophysiologically determined disorder involving disruptions in various cognitive functions, particularly phonological processing. This results in challenges with sound recognition, decoding, and word retrieval, which compromise reading fluency and comprehension. Affected students may experience heightened cognitive load, particularly under stress or fatigue.

 

Research Distinguishing Dyslexia and Irlen Syndrome

A considerable body of independent research supports the classification of dyslexia and Irlen syndrome (also referred to as scotopic sensitivity syndrome) as distinct conditions. Key studies include Helen Irlen’s foundational study introducing Irlen Syndrome as a perceptual processing disorder and highlighting that the related reading difficulties stem from visual distortions rather than phonological deficits,9 and more recent contributions by Čelešnik.5, 10-12 These studies demonstrate distinct etiologies, symptomatology, and treatment pathways for each condition.13-22

As outlined in The Concepts of Work – Program of Elementary School Education (2018),16 individuals may exhibit only a subset of symptoms associated with either disorder. This underlines the need for careful, individualized assessment, especially when addressing learning and reading difficulties in children.

 

Synthesis of Findings

Drawing upon literature and clinical experience, we present a synthesized understanding of dyslexia and Irlen syndrome as separate yet sometimes comorbid conditions. Table 1 below delineates the unique and shared characteristics of each.

 

Table 1: Characteristics of Dyslexia and Irlen Syndrome

Source: Maja Volk, Petra Vovk, and Nina Čelešnik

 

Despite shared reading challenges, the table demonstrates that dyslexia predominantly involves language processing deficits, while Irlen syndrome presents with sensory-visual disturbances. Awareness of these differences enables accurate diagnosis and effective intervention.

 

Proposed Diagnostic and Treatment Sequence:

  1. Comprehensive Vision Examination – by an optometrist familiar with Irlen syndrome, and if necessary, an ophthalmologist.
  2. Irlen Self-Test – followed by screening with a certified Irlen screener if warranted, using Irlen overlays.
  3. Irlen Diagnostic Assessment – to determine suitability for customized Irlen spectral filters.
  4. Formal Assessment for Dyslexia
  5. Targeted Intervention for Dyslexia

 

Conclusion

The literature supports the understanding that dyslexia and Irlen syndrome are distinct disorders, despite overlapping symptoms. Accurate identification of each condition is critical for implementing effective and timely interventions.

Educators, particularly classroom teachers, play a pivotal role in the early identification of students with learning difficulties. They must advocate for these students by involving counseling services and maintaining consistent communication with families. Children benefit greatly from the support of compassionate, informed adults throughout the diagnostic and intervention process. Trust, patience, and ongoing guidance are foundational to fostering successful outcomes for students facing dyslexia, Irlen syndrome, or both.

 

References

  1. Irlen, H. (2005). Reading by the colors. Overcoming dyslexia and other reading disabilities through the Irlen method. New York: Penguin Group.
  2. Irlen, H. (2010). The Irlen revolution. USA: SquereOne Publishers.
  3. Irlen, H. (2017). Sports concussions and getting back in the game of life. USA: Helen Irlen.
  4. Robinson, G. L. in Conway, R. N. F. (1996). Irlen lenses and adults: Preliminary results of a controlled study of reading speed, accuracy and comprehension. Conference papers. Irlen Institute Fourth International Conference, New Orleans, 27–30.
  5. Čelešnik Kozamernik, N. (2021). Učinki nošenja očal z barvnimi filtri Irlen na samospoštovanje, zadovoljstvo v partnerskem odnosu, zadovoljstvo z življenjem, izgorelost in na druga področja težav pri odrasli slepi osebi z dojemom svetlobe in s skotopičnim sindromom – študija primera. Kairos, Slovenska revija za psihoterapijo, 2021, 15, no. 1–2: 259–279, https://www.skzp.si/2021/07/15/izsla-je-nova-stevilka-revije-kairos-4/
  6. Whiting, P. in Robinson, G. L. (1988). Using Irlen coloured lenses for reading: A clinical study. Australian Educational and Developmental Psychologist, 5, 7–10.
  7. Wajuihian, S. O. in Naidoo, K. S. (2012). Dyslexia: An overview. Optometry & Vision Development, 24–33.
  8. Singleton, C. in Henderson I. (2007). Computerized screening for visual stress in children with dyslexia. Dyslexia, 13, 130–151.
  9. Irlen, H. (1983, August). Successful treatment of learning disabilities. In 91st annual convention of the American Psychological Association, Anaheim, CA(Vol. 5).
  10. Čelešnik, N. (2022). Skotopični sindrom oz. sindrom Helen Irlen: vpliv na življenje posameznikov in pomen ustrezne oftalmološke/optometristične diagnostike vida. Mednarodna konferenca EDUvision 2022, 916–931, Ljubljana, 2022. http://www.eduvision.si/zbornik-prispevkov (15th February 2023).
  11. Čelešnik, N. (2023a). Skotopični sindrom oz. sindrom Helen Irlen in disleksija v slovenski otroški literaturi. Razredni pouk, Strokovna revija za raziskovanje in razvoj področja razrednega pouka, XXV, 2023, no. 1, p. 43 to 48.
  12. Čelešnik, N. (2023b). Disleksija in skotopični sindrom oz. sindrom Helen Irlen – 2 težavi, ki se lahko prekrivata. Mednarodna konferenca EDUvision 2023, 1162–1173, Ljubljana, 2023. https://www.eduvision.si/Content/Docs/Zbornik_EDUvision_23_splet.pdf (15th January 2024).
  13. Wesson, M. D. (1993). Diagnosis and management of reading dysfunction by the primary care optometrist. Optom Vis Sci, 70, 357–368.
  14. Carroll T. A., Mullaney P. in Eustace P. (1994). Dark adaptation in disabled readers screened for Scotopic Sensitivity Syndrome. Perceptual Motor Skills, 131–141.
  15. Evans B. J. W., Cook A., Richards I. L. in Drasdo N. (1994). Effect of pattern glare and colored overlays on a simulated-reading task in dyslexics and normal readers. Optom Vis Sci 71(10):619–628.
  16. Kriss, I., & Evans, B. J. W. (2005). The relationship between dyslexia and Meares-Irlen syndrome. Clinical and Experimental Optometry, 88(1), 5–12. https://doi.org/10.1111/j.1444-0938.2005.tb06643.x
  17. Singleton, C., & Henderson, L. M. (2007). Computerized screening for visual stress in children with dyslexia. Dyslexia, 13(2), 130–151. https://doi.org/10.1002/dys.331
  18. Nandakumar, K., & Leat, S. J. (2008). Dyslexia: A review of two theories. Clinical and Experimental Optometry, 91(3), 333–340. https://doi.org/10.1111/j.1444-0938.2008.00263.x
  19. Evans, B. J. W., & Allen, P. M. (2016). A systematic review of controlled trials on visual stress using Intuitive Overlays or the Intuitive Colorimeter. Journal of Optometry, 9(4), 205–218. https://doi.org/10.1016/j.optom.2016.07.001
  20. Uccula, A., Enna, M., & Mulatti, C. (2014). Colors, colored overlays, and reading skills. Frontiers in Psychology, 5, 833. https://doi.org/10.3389/fpsyg.2014.00833
  21. Chouinard, B. D., Zhou, C., Hrybouski, S., & McQuarrie, L. (2012). Distinct neural correlates of dyslexia and visual stress in children: An fMRI study. NeuroImage, 60(Supplement 1), S69. (Note: Abstract only; for full citation, see conference proceedings.)
  22. Robinson, G. L., Foreman, P. J., Dear, K. G. B., & Sparkes, D. (2004). The familial incidence of symptoms of Scotopic Sensitivity/Irlen Syndrome and its association with dyslexia. Journal of Learning Disabilities, 37(2), 131–137. https://doi.org/10.1177/00222194040370020401
  23. Magajna, L., Kavkler, M., Čečinovič Vogrinčič, G., Pečjak, S. in Bregar Golobič, K. (2018). Koncept dela – program osnovnošolskega izobraževanja, učne težave v osnovni šoli. Ljubljana: Zavod Republike Slovenija za šolstvo.
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