Tuesday, October 05, 2004

An increase in the number of children and adults who have difficulty reading has become a serious social and workplace problem. The etiology of reading disorders is not completely understood and the causes are multifactorial, as are the treatment methodologies. Recent evidence suggests that physiological and visual deficits exist in the majority of reading disabled individuals.1
One method proposed to address the problem of reading difficulty, dyslexia or other related reading or learning problems is the use of specially tinted lenses or colored filters. These lenses and/or filters are purported to improve reading ability and visual perception, increase sustained reading time, and eliminate symptoms associated with reading such as light sensitivity, headaches, blurring of print, and watery eyes. These symptoms and reading problems are reportedly due to an underlying visual perception dysfunction described by Irlen as "scotopic sensitivity syndrome"(SSS).2,3
A comprehensive review of the available scientific literature regarding the effectiveness of tinted lenses or filters revealed the following:
1. Current research does not support the validity or presence of an actual visual perceptual dysfunction termed "scotopic sensitivity syndrome." Therefore the use of this term is meaningless.
2. Results of testing utilized to determine the most appropriate color or filter are not repeatable.4,5
3. There is evidence that the underlying symptoms associated with SSS are related to identifiable vision anomalies, e.g., accommodative and convergence dysfunctions, in the majority of patients.6,7,8 Reduced amplitudes of accommodation and vergence and poor visual acuities are factors correlating with SSS but they may not be the underlying cause.3,9 Such conditions return to normal function when appropriately treated with vision therapy.10 When patients exhibiting SSS were treated with vision therapy, their symptoms were relieved, they no longer demonstrated a need for the tinted lenses, and they were no longer classified as exhibiting SSS.4
4. The results of research on the effectiveness of tinted lenses or filters vary. One randomized controlled trial has demonstrated that children with reading difficulties who were prescribed colored filters did experience reduced symptoms of asthenopia; however, the filters may need to be individually and precisely prescribed and the mechanism for the benefit from colored filters is not solely a placebo effect.11 Colored filters, overlays or lenses,12 may be regarded as a reading aid useful for some dyslexic children rather than a cure for dyslexia.13 Other researchers failed to find improvement in comprehension scores in readers using tinted lenses.14,15 Additionally, researchers have found no improvement in accommodative accuracy at nearpoint when using tinted lenses or filters.16
Until more carefully controlled clinical research studies are conducted, reading and learning disabled individuals, parents and the professionals who work with them should remain skeptical of the efficacy of any undocumented claims. Future research must address the sub-typing of reading disabilities and the differential response to different treatments.17,18 Therefore, it is the position of the American Optometric Association that:
1. There is currently no scientific research to support the "scotopic sensitivity syndrome" hypothesis.
2. Undetected binocular vision problems may be a factor in individuals who exhibit the symptoms of the so-called "scotopic sensitivity syndrome." A comprehensive eye/vision examination with particular emphasis on binocular vision function is recommended for all individuals experiencing reading or learning difficulties, as well as those showing signs and symptoms of visual efficiency problems.
3. The American Optometric Association encourages and supports further research to investigate the effect that specifically tinted lenses and filters may have on a person's visual function related to reading performance.
4. Finally, optometrists must contribute to the multidisciplinary approach for the diagnosis and management of reading and learning disorders.

1. A Joint Organizational Policy Statement on Vision, Learning and Dyslexia. J Am Optom Assoc, 1997; 68(5):284-5.
2. Irlen HL. Scotopic sensitivity/Irlen syndrome. Hypothesis and explanation of the syndrome. J Behav Opt, 1994; 5:62-6.
3. Evans BJW, Wilkins AJ, Busby A, et al. A preliminary investigation into the aetiology of Meares-Irlen syndrome. Ophthal Physiol Opt, 1996; 16(4):286-96.
4. Blaskey P, Scheiman M, Parisi M, et al. The effectiveness of Irlen lenses for improving reading performance: A pilot study. J. Learn Disabil, 1990; 23(10):604-12.
5. Solan HA, Richman J. Irlen lenses: A critical appraisal. J Am Optom Assoc, 1990; 61:789-96.
6. Scheiman MM, Blasky P, Ciner EB, et al. Vision characteristics of individuals identified as Irlen Filter candidates. J Am Optom Assoc, 1990; 61:600-5.
7. Hoyt CS. Irlen lenses and reading difficulties. J Learn Disabil, 1990; 23(10):624-6.
8. Lopez R, Yolton RL, Kohl P, et al. Comparison of Irlen Scotopic Sensitivity Syndrome test results to academic and visual performance data. J Am Optom Assoc, 1994; 65:705-14.
9. Solan HA, Brannon JR, Ficarra AP, et al. Transient and sustained processing: Effects of varying luminance and wavelength on reading comprehension. J Am Optom Assoc, 1997; 68:503-10.
10. Special Report. The efficacy of optometric vision therapy. J Am Optom Assoc, 1988; 59:95-105.
11. Wilkins AJ, Evans BJW, Brown J, et al. Double-masked placebo-controlled trial of precision spectral filters for children who use coloured overlays. Ophthal Physiol Opt, 1994; 14:365-70.
12. Wilkins AJ. Technical note: Overlays for classroom and optometric use. Ophthal Physiol Opt, 1994; 14:97-9.
13. Gordon GC. Visual Anomalies in dyslexia: a review of the literature. Br Orthopt J, 1997; 54:34-9.
14. Fletcher J, Martinez G. An eye-movement analysis of the effect of Scotopic Sensitivity Correction of Parsing and Comprehension. J Learn Disab, 1994; 27(1):67-70.
15. Menacker SJ, Breton ME, Brenton ML, et al. Do tinted lenses improve the reading performance of dyslexic children? A cohort study. Arch Ophthalmol, 1993; 111:213-8.
16. Ciuffreda KJ, Scheiman M, Ong E, et al. Irlen lenses do not improve accommodative accuracy at near. Opt Vis Sci, 1997; 74(5):298-302.
17. Ridder W, Borsting E, Cooper M, et al. Not all dyslexics are created equal. Optom Vis Sci, 1997; 74:99-104.
18. Garzia RP, Nicholson SB. Vision function and reading disability: an optometric viewpoint. J Am Optom Assoc, 1990; 61:88-97.


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