Irlen syndrome: systematic review and level of evidence analysis

Scotopic sensitivity syndrome, later called Meares-Irlen syndrome or simply Irlen syndrome (IS) has been described as symptoms of poor reading ability due to poor color matching and distorted graphic images. Individuals with this syndrome are considered slow, ineffective readers with low comprehension and visual fatigue. It is still uncertain whether the disease pathophysiology is an independent entity or part of the dyslexia spectrum. Nevertheless, treatments with lenses and colored filters have been proposed to alleviate the effect of the luminous contrast and improve patients’ reading performance. However, no evidence of treatment effectiveness has been achieved.

Objective:

The aim of the present study was to obtain evidence about IS etiology, diagnosis and intervention efficacy.

Methods:

A systematic review was performed covering the available studies on IS, assessing the available data according to their level of evidence, focusing on diagnostic tools, proposed interventions and related outcomes.

Results:

The data showed high heterogeneity among studies, and lack of evidence on the existence of IS and treatment effectiveness.

Conclusion:

The syndrome as described, as well as its treatments, require further strong evidence.

Keywords:
Reading disorders; systematic review; evidence-based medicine; meares-irlen syndrome; colored lenses

Reference	Population		Study type	Diagnostic tool	Intervention	Main findings	Level of evidence
Reference	Population	Comparison group	Study type	Diagnostic tool	Intervention	Main findings	Level of evidence
O'Connor et al. 1990¹⁴14 O'Connor PD, Sofo F, Kendall L, Olsen G. Reading disabilities and the effects of colored filters. J Learn Disabil. 1990;23(10):597-603. DOI:10.1177/002221949002301006 https://doi.org/10.1177/0022219490023010...	92 Children	Non-scotopic	CC	IDPS NARA FRI	PCOF DCOF	More visual comfort. Gained reading rate. Filter improved reading.	3
Scheiman et al. 1990¹⁵15 Scheiman M, Blaskey P, Ciner EB, Gallaway M, Parisi M, Pollack K, Selznick R. Vision characteristics of individuals identified as Irlen Filter candidates. J Am Optom Assoc. 1990; 61(8): 600-5. PMID: 2394899	Varied (age 10 to 49) n = 39	No control	CH	IDPS		More visual comfort. Gained reading rate. Filter improved reading.	4
Blaskey et al. 1990¹⁶16 Blaskey P, Scheiman M, Parisi M, Ciner EB, Gallaway M, Selznick R. The effectiveness of Irlen filters for improving reading performance: a pilot study. J Learn Disabil.1990;23(10):604-12. DOI:10.1177/002221949002301007 https://doi.org/10.1177/0022219490023010...	Varied (age 9 to 51) 12 male; 18 female	Non-scotopic	CCH	IDPS	IF	Self-declared more comfort. No gain in reading. Irlen filter group showed no significant gains.	4
Robinson, Conway 1990¹⁷17 Robinson GL, Conway RN. The effects of Irlen colored lenses on students' specific reading skills and their perception of ability: A 12-month validity study. J Learning Disabil. 1990;23(10):589-596. DOI:10.1177/002221949002301005 https://doi.org/10.1177/0022219490023010...	Varied (age 9 to 15) 33 males, 11 female	No control	CH	IDPS NARA SPAS	IF	Improvements on Irlen tests. No improvements on NARA and SPAS. Filter improved reading accuracy and comprehension, but not rate.	4
Martin et al. 1993¹⁸18 Martin F, Mackenzie B, Lovegrove W, McNicol D. Irlen lenses in the treatment of specific reading disability: An evaluation of outcomes and processes. Australian J Psychol 1993; 45(3): 141-150. DOI:10.1080/00049539308259131 https://doi.org/10.1080/0004953930825913...	7th graders n = 60	Normal readers	CCH	LILP NARA RPM NWT	IL/COF	No difference among groups. No gain in reading. No improvement with IL/COF.	4
Carrol et al. 1994¹⁹19 Carroll TA, Mullaney P, Eustace P. Dark adaptation in disabled readers screened for Scotopic Sensitivity Syndrome. Percept Mot Skills. 1994; 78(1):131-41. DOI: 10.2466/pms.1994.78.1.131 https://doi.org/10.2466/pms.1994.78.1.13...	Varied (age 10 to 20) n = 64	23 normal readers	CC	IDPS	Dark adaptation	No difference among groups. Inconclusive.	4
Evans et al. 1994²⁰20 Evans BJ, Cook A, Richards IL, Drasdo N. Effect of pattern glare and colored overlays on a stimulated-reading task in dyslexics and normal readers. Optom Vis Sci 1994; 71(10): 619-28. DOI: 10.1097/00006324-199410000-00004 https://doi.org/10.1097/00006324-1994100...	Varied (mean age 22; age 7 to 12) n = 82	11 normal readers	CC	PGT SRVST	COF	No difference with lenses. No differences in PGT among groups.	4
				NARA		Borderline significance supporting lenses.
Lopez et al. 1994²¹21 Lopez R, Yolton RL, Kohl P, Smith DL, Saxerud MH. Comparison of Irlen scotopic sensitivity syndrome test results to academic and visual performance data. J Am Optom Assoc. 1994; 65(10): 705-14. PMID: 7995893	Varied (children) 39	15 with “academic problems”	CC	ISSST	PCOF	No difference in PCOF users. No difference in academic performance. More research needed.	4
Sawyer et al. 1994²²22 Sawyer C, Taylor S, Willcocks S. Transparent coloured overlays and specific learning difficulties. AEP (Association of Educational Psychologists) Journal. 1994;(4), 217-220. DOI:10.1080/0266736940090404. https://doi.org/10.1080/0266736940090404...	Varied (age 7 to 15) n = 271	86 children without referred reading problems	CC	SRTa	PCOF	Differences inside the instrument variation. No improvement in reading. Very low effect; other refractive problems as the cause; more investigation needed.	4
Wilkins et al. 1994²³23 Wilkins AJ, Evans BJW, Brown JA, Busby AE, Wingfield AE, Jeanes RJ, Bald J. Double masked placebo controlled trial of precision spectral filters in children who use coloured overlays. Ophthal Physiol Opt 1994;14:365-370. DOI:10.1111/j.1475-1313.1994.tb00126.x https://doi.org/10.1111/j.1475-1313.1994...	Varied (age 9 to 15) n = 37	Children with reported failing in reading, with and without lenses.	PCT	ISSST NARA	Intuitive Colorimeter®	No differences on NARA and other symptoms evaluated. No gain in reading. Lenses ameliorate symptoms of IS.	2
Evans et al. 1995²⁴24 Evans BJW, Busby A, Jeanes R, Wilkins AJ. Optometric correlates of Meares-Irlen Syndrome: a Matched group study. Ophthal Physiol Opt 1995; 15(5): 481-7. DOI:10.1046/j.1475-1313.1995.9500063j.x https://doi.org/10.1046/j.1475-1313.1995...	Children aged 12 n = 42	26 nonresponsive to COF	CC	ISSST SRTb NARA PGT	Intuitive Colorimeter®	No differences on NARA or symptoms. No gain in reading. Suggests caution on data interpretation due to high similarity among case and control groups.	4
	Adult and children			Interview		No differences on WRAT-R.
Spafford et al. 1995²⁵25 Spafford CS, Grosser GS, Donatelle JR, Squillace SR, Dana JP. Contrast sensitivity differences between proficient and disabled readers using colored lenses. J Learn Disabil. 1995;28(4):240-52. DOI:10.1177/002221949502800406 https://doi.org/10.1177/0022219495028004...	4 children, 4 adults	8 matched controls	CC	WRAT-R	COF	Lens color not critical for reading. Inconclusive; use of any unproven therapy could delay appropriate treatment.	4
Evans et al. 1996²⁶26 Evans BJW, Wilkins AJ, Brown J, Busby A, Wingfield A, Jeanes R, Bald J. A preliminary investigation into the aetiology of Meares-Irlen syndrome. Ophthal Physiol Opt 1996; 16(4): 286-96. https://doi.org/10.1046/j.1475-1313.1996.95001190.x https://doi.org/10.1046/j.1475-1313.1996...	Reports on sample from previous study (25)	Participants report failing in reading, with/ without lenses.	CC	ISSST PGT Optometrics	COF	No difference in pattern glare and IS. Ocular motor anomalies correlate to IS. Method psychophysically primitive; optometric anomalies are priority in treatment.	4
Ciuffreda et al. 1997²⁷27 Ciuffreda KJ, Scheiman M, Ong E, Rosenfield M, Solan HA. Irlen lenses do not improve accommodative accuracy at near. Optom Vis Sci. 1997;74(5):298-302. DOI: 10.1097/00006324-199705000-00026 https://doi.org/10.1097/00006324-1997050...	Adults (age 18 to 39) 2 males; 6 females	No	OB/CR	LILP	COF	No positive effect on steady-state accommodation. No improvement on accuracy; participants in fact needed other vision intervention.	4
Evans et al 1999²⁸28 Evans BJ, Patel R, Wilkins AJ, Lightstone A, Eperjesi F, Speedwell L, Duffy J. A review of the management of 323 consecutive patients seen in a specific learning difficulties clinic. Ophthalmic Physiol Opt. 1999;19(6):454-66. DOI:10.1111/j.1475-1313.1999.00465.x https://doi.org/10.1111/j.1475-1313.1999...	Varied (age 4 to 73) N=323	No	RP/EP	ISSST IO IC	PCOF	Patient perception of improvement. 73% still wearing tinted lenses 1,5 yrs after.	4
Robinson, Foreman 1999²⁹29 Robinson GL, Foreman PJ. Scotopic sensitivity/Irlen syndrome and the use of coloured filters: a long-term placebo-controlled study of reading strategies using analysis of miscue. Percept Mot Skills 1999;88(1):35-52. DOI:10.2466/pms.1999.88.1.35 https://doi.org/10.2466/pms.1999.88.1.35...	Children (age 9 to 13) n = 113	35 controls with reading problems	PCT	ISSST/LILP NARA	IL	No difference among groups. No modification related to other groups. No improvements at all.	2
Robinson, Foreman 1999³⁰30 Robinson GL, Foreman PJ. Scotopic sensitivity/Irlen syndrome and the use of coloured filters: a long-term placebo controlled and masked study of reading achievement and perception of ability. Percept Mot Skills.1999;89(1): 83-113. DOI:10.2466/pms.1999.89.1.83 https://doi.org/10.2466/pms.1999.89.1.83...	Same as previous (32) n = 88	28 controls from previous study (32)	PCT	ISSST/LILP NARA	IL	Statistical difference among selected groups. Improvements on some tasks.	2
Robinson et al 2000³¹31 Robinson GL, Foreman PJ, Dear KB. The familial incidence of symptoms of scotopic sensitivity/Irlen syndrome: comparison of referred and mass-screened groups. Percept Mot Skills. 2000;91(3):707-24. DOI:10.2466/pms.2000.91.3.707 https://doi.org/10.2466/pms.2000.91.3.70...	Varied (age 9 to 13) n = 158	125 referred 33 screening	PP	ISSST IS	-	84% of parents with IS No difference among groups Prevalence of symptoms on males	4
Bouldoukian et al. 2002³²32 Bouldoukian J, Wilkins AJ, Evans BJW. Randomised controlled trial of the effect of coloured overlays on the rate of reading of people with specific learning difficulties. Ophthalmic Physiol Optics. 2002;22(1):55-60. DOI:10.1046/j.1475-1313.2002.00002.x https://doi.org/10.1046/j.1475-1313.2002...	Varied (age 7 to 40) n = 33	With/without overlay	CC	IO WRRT	IO	Increased reading rate due to IO. Increased rate due to practice on same test. IO improved rate of reading. No placebo effect.	2
Evans, Joseph 2002³³33 Evans BJ, Joseph F. The effect of coloured filters on the rate of reading in an adult student population. Ophthalmic Physiol Opt. 2002;22(6):535-45. DOI:10.1046/j.1475-1313.2002.00071.x https://doi.org/10.1046/j.1475-1313.2002...	University students n = 113	13 participants without complaints	CC	IO WRRT	IO	More than 90% was 3,8% faster with IO. 21 participants stated that IO worsened perception. One-third of the sample shows benefit on reading (>5%) with colored lenses. Prevalence in adults equal in children.	4
Scott et al. 2002³⁴34 Scott L, McWhinnie H, Taylor L, Stevenson N, Irons P, Lewis E, Evans M, Evans B, Wilkins A. Coloured overlays in schools: Orthoptic and optometric findings. Ophthalmic Physiol Opt. 2002;22(2):156-165. DOI: 10.1046/j.1475-1313.2002.00009.x https://doi.org/10.1046/j.1475-1313.2002...	Children (age 10 to 12) n = 94	63 without IS criterion	CC	IO, WRRT, LRT	IO	No difference among groups with and without IO. Supports the beneficial effects of IO.	4
	Children					No significant difference among groups; no increase in reading speed.
Northway, 2003³⁵35 Northway N. Predicting the continued use of overlays in school children - A comparison of the Developmental Eye Movement test and the Rate of Reading test. Ophthalmic Physiol Opt. 2003;23(5):457-464. https://doi.org/10.1046/j.1475-1313.2003.00144.x https://doi.org/10.1046/j.1475-1313.2003...	(age 9 to 15) n = 64	With/without lenses	OB/RP	IO, WRRT, DEM	IO	Improvement only on WRRT, not DEM. Visual symptomatic children found a preferred colored overlay of benefit.	4
Waldie, Wilkins, 2004³⁶36 Waldie M, Wilkins A. How big does a coloured overlay have to be? Ophthalmic Physiol Opt. 2004;24(1):57-60. DOI:10.1046/j.1475-1313.2003.00169.x https://doi.org/10.1046/j.1475-1313.2003...	Children (age mean = 9.4) n = 23	-	OB	IO	IO	No significant difference among groups	4
Kriss, Evans, 2005³⁷37 Kriss I, Evans BJW. The Relationship between Dyslexia and Meares-Irlen Syndrome. J Res Reading. 2005;28(3):350-364. DOI:10.1111/j.1467-9817.2005.00274.x https://doi.org/10.1111/j.1467-9817.2005...	Children (age 7 to 12) n = 64 dyslexic	32 dyslexic; with / without IO	CC with 2x2 mixed factorial	IO, WRRT	IO	Control group w. higher scores in WRRT; 34% of dyslexic group up to 8% faster on WRRT with IO. IS affected normal readers. Although no significant difference in prevalence, more IS in dyslexic children.	4
Hollis, Allen, 2006³⁸38 Hollis J, Allen PM. Screening for Meares-Irlen sensitivity in adults: can assessment methods predict changes in reading speed? Ophthalmic Physiol Opt. 2006;26(6):566-71. DOI:10.1111/j.1475-1313.2006.00401.x https://doi.org/10.1111/j.1475-1313.2006...	Adults (age 18 to 58) n = 58	-	OB/PP	IO WRRT PGT	IO	No benefit of IO for normal. Self reported symptom. Reading speed test recommended.	4
Riddel et al. 2006³⁹39 Riddell PM, Wilkins A, Hainline L. The effect of coloured lenses on the visual evoked response in children with visual stress. Optometry Vision Sci. 2006;83(5):299-305. DOI:10.1097/01.opx.0000216125.83236.af https://doi.org/10.1097/01.opx.000021612...	Children (age 9 to 16) 10 (6 male; 4 female)	-	OB/CS	Previous IO users; VEP	IO	No significant differences among groups. No objective VEP differences can be measured in all children who claim benefit from the use of colored lenses.	4
Kruk et al. 2008⁴⁰40 Kruk R, Sumbler K, Willows D. Visual processing characteristics of children with Meares-Irlen syndrome. Ophthalmic Physiol Opt 2008; 28(1): 35-46. DOI:10.1111/j.1475-1313.2007.00532.x https://doi.org/10.1111/j.1475-1313.2007...	Children (age 9 to 10) n = 36	18 non-dyslexic	OB/PP	IRPS, LILP, WRAT	No intervention	No difference among normal readers and dyslexic. IS diagnosis was not an indicator of visual deficit subtype of dyslexia. No relationship between IS and reading performance.	4
	Children					NARA and SDMT improved in all groups.
	(age 7 to 11)					IDPS improved in placebo and experimental, and decreased in control.
Mitchell et al. 2008¹⁰10 Mitchell C, Mansfield D, Rautenbach S. Coloured filters and reading accuracy, comprehension and rate: A placebocontrolled study. Perceptual Motor Skills. 2008;106(2):517-532. DOI:10.2466/PMS.106.2.517-532 https://doi.org/10.2466/PMS.106.2.517-53... .	n = 49 (35 male, 14 female)	With/without lenses	PCT	IDPS, NARA, SDMT, IC	IO	No difference among placebo and experimental groups.	2
						Clear definition of visuoperceptual reading disabilities impaired the possible conclusion and experimental design.
Nichols et al. 2009⁴¹41 Nichols SA, McLeod JS, Holder RL, McLeod HS. Screening for dyslexia, dyspraxia and Meares-Irlen syndrome in higher education. Dyslexia 2009;15(1): 42-60. DOI:10.1002/dys.382 https://doi.org/10.1002/dys.382...	University students (mean age 23.4) n = 74 (7 male)	-	OB/PP	IO, WRRT, LADS	-	24% revealed IS. LADS occurred within IS. More research is needed.	4
	Adults					No improvement in reading.
Taub et al. 2009⁴²42 Taub MB, Shallo-Hoffmann J, Steinman S, Steinman B. The effect of colored overlays on reading eye movements in adults. J Behav Optometry. 2009;20(6), 143-149.	N = 60	No referred symptoms of IS	OB/PP	Visagraph®	Colored lenses	No difference among groups. The IS symptoms were related to binocular/accommodative vision disorder.	4
Ritchie et al. 2011⁴³43 Ritchie SJ, Della Sala S, McIntosh RD. Irlen colored overlays do not alleviate reading difficulties. Pediatrics 2011;128(4):932-8. DOI:10.1542/peds.2011-0314 https://doi.org/10.1542/peds.2011-0314...	Children (primary school) n = 75	-	OB/PP	LILT, WRRT, MMSE, GORT	IO	No gain in reading. No difference among groups for all tests. More orthoptic problem in IS group.	3
Vidal-López 2011⁴⁴44 Vidal-López J. The role of attributional bias and visual stress on the improvement of reading speed using colored filters. Percept Mot Skills. 2011;112(3):770-82. DOI: 10.2466/15.19.24.PMS.112.3.770-782 https://doi.org/10.2466/15.19.24.PMS.112...	Secondary students (mean age 12) n = 54 (28 males)	27 paired individuals without IS	CC	PGT, IO, ISSST, PROLEC, SI, VS-SDT	IO	No differences with IO users. Attributional bias. Did not support the visual stress theory. Suggested strong motivational effects.	3
Ritchie et al. 2012⁴⁵45 Ritchie SJ, Della Sala S, McIntosh RD. Irlen colored filters in the classroom: A 1-year follow-up. Mind Brain Educ. 2012;6(2):74-80. DOI:10.1111/j.1751-228X.2012.01139.x https://doi.org/10.1111/j.1751-228X.2012...	IS children (mean age 9) n = 18	10 non-IS	CC/CH (1yr)	WRRT, MMSE, GORT	IO	No difference among groups. No improvements with IO after 1yr. No benefits to reading. No effects in short or long term.	4
Chang et al. 2014⁴⁶46 Chang M, Kim SH, Kim JY, Cho YA. Specific visual symptoms and signs of Meares-Irlen syndrome in Korean. Korean J Ophthalmol. 2014; 28(2):159-63. DOI:10.3341/kjo.2014.28.2.159 https://doi.org/10.3341/kjo.2014.28.2.15...	IS students (age 8 to 34) n = 34	11 dyslexic	CC	Not specified	IO Korea	Improvement needed on IS diagnosis. Lenses efficacy should be measured. Objectively testing for the syndrome. Further studies required.	4
Kim et al. 2015⁴⁷47 Kim JH, Seo HJ, Ha SG, Kim SH. Functional magnetic resonance imaging findings in Meares-Irlen syndrome: a pilot sudy. Korean J Ophthalmol. 2015;29(2):121-5. DOI:10.3341/kjo.2015.29.2.121 https://doi.org/10.3341/kjo.2015.29.2.12...	Varied (age 13 to 41) n = 15	-	OB/PP	Self-reported IS	IO	Brain reacts different with and without lenses. Temporal regions activate after lenses.	4
Loew et al. 2015⁴⁸48 Loew SJ, Rodríguez C, Marsh NV, Jones GL, Núñez JC, Watson K. Levels of Visual Stress in Proficient Readers: Effects of Spectral Filtering of Fluorescent Lighting on Reading Discomfort. Span J Psychol. 2015;10(18):E58. DOI:10.1017/sjp.2015.59 https://doi.org/10.1017/sjp.2015.59...	Non-clinical samples (age 21 to 60) n = 24 (9 males, 15 females)	With/without lenses.	OB	Self-reported; WRRT; PROLEC; IO	Tinted lenses	No differences in reading speeds among participants with and without lenses. Fluorescent lighting can affect readers at all levels of proficiency.	4
Alanazi et al. 2016⁴⁹49 Alanazi MA, Alanazi SA, Osuagwu UL. Evaluation of visual stress symptoms in age-matched dyslexic, Meares-Irlen Syndrome and normal adults. Int J Ophthalmol 2016; 9(4): 617-24. DOI: 10.18240/ijo.2016.04.24 https://doi.org/10.18240/ijo.2016.04.24...	Varied (age 18 to 30) n = 450	Female medical students	EP	Self-reported	Not defined	2% dyslexic 6% IS 33% dyslexic and IS	4
Garcia et al. 2017⁵⁰50 Garcia ACO, Momensohn-Santos TM, Vilhena DA. Effects of Spectral Overlays on Reading Performance of Brazilian Elementary School Children. Folia Phoniatr Logop. 2017;69(5-6):219-225. DOI: 10.1159/000484139. https://doi.org/10.1159/000484139....	Children (age 9 to 12) n = 68 (36 male, 32 female)	-	OB/PP	IRPS/OO, WRRT	ISOs	No significant gain in reading. 9 individuals reported 6% increase in reading speed on WRRT. Filters improved reading rate.	4

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[1] Correspondence: Erik Montagna; Faculdade de Medicina do ABC - Pós-Graduação; Av Lauro Gomes, 2000; 09060-870 Santo Andre SP, Brasil; E-mail: erik. montagna@fmabc.br