Pritam Dutta, M.Optom, FAAO

Instructor Neuro-Optometry, Vision Science Academy



Meares–Irlen (MI) syndrome or visual stress syndrome is a perceptual processing difficulty characterized by difficulties with reading and symptoms of eye strain and headaches. It is accompanied with visual perceptual distortions such as blurring, double patterns and movement of print on the page. Meares–Irlen syndrome (previously known as scotopic Sensitivity syndrome) is more likely prevalent in dyslexics.(1) However the symptoms would also include lack of concentration while reading along with page text appearing too bright, pattern distraction from space between the lines and the words, slow in reading fluency after a prolonged exposure, headaches on viewing text with pattern or flickering lights, visual fatigue with prolonged exposure to reading, colours and shapes pattern appearing on the reading page. (2) Changes in the visual cortex as deficits in the magnocellular system (responsible for reading and coordinating the visual cortex information on movements) are the underlying pathophysiology of MI syndrome. (3)

Role of coloured lenses in Meares-Irlen syndrome

Existing literature suggest that the symptoms mitigate with usage of coloured filters of a specific tint (Table 1). Filters and coloured lenses are generally recommended for transforming the light spectrum and reducing the intensity between light and dark to aid visual and retinal photoreceptor adaptation. Moreover, since coloured lenses were one of the recognition methods proposed to evaluate MI syndrome, it was indeed a confusing factor.

Table 1: Recent research on Meares–Irlen syndrome and coloured lenses using variable mode of intervention

Study Purpose Intervention Findings
Chang et al. (2014) (4) Discrimination of visual signs and symptoms of MI syndrome and non-specific dyslexia from other eye diseases Intuitive Overlays Common symptoms in MI subjects included doubling, difficulty in bright lights and moving lines. 3/4th of the subjects improved in symptoms using tinted lenses.
Kim et al. (2015)(5) Investigating the pattern of functional MRI while reading sentences before and after using coloured tinted lenses Intuitive overlays Activation in the left middle and supero-temporal gyrus while reading using coloured lenses leading to improvement in the reading speed more than 20 % compared to before lens session.
Loew et al. (2015) (6) Investigating visual discomfort in expert readers under standard and spectrally filtered fluorescent lighting Tinted lenses Visual stress symptoms might occur in proficient readers; not confining it to MI syndrome.
Alanazi et al. (2016)(7) Determining the level of visual stress in MI syndrome and normal subjects Not defined MI subjects showed significant higher TVSS scores (p=0.002), NCQ (p=0.006) and CQ (p=0.008) visual stress scores than controlled arm
Garcia et al. (2017)(8) Examining the effects of spectral overlays on reading performance Irlen Spectral Overlays set Spectral overlays improve the reading performance especially in individuals with severe visual discomfort
* TVSS: Total visual stress score; CQ: Critical questions; NCQ: Non-critical questions

It is hypothesized that the pyramidal neurons share inhibitory interneurons and a strong stimulation to it might lead to local depletion, resulting a spread of excitation.(9) This spread of excitation leads to inappropriate firing of cortical neurons causing perception of illusions and distortions. Therefore, by means of topographic encoding of chromaticity in the cortical areas, the colours reorganize excitation with large deviation in spectral sensitivity of cortical neurons. Thus, colours that are comfortable reduce the excitation in hyper-excitable areas. (10) Moreover, apart from colours, few modifications in the working environment can also be made to enhance their daily activities (Table 2).  

Colour selection using Intuitive colorimeter

The colour of the lens could be selected using an instrument called Intuitive colorimeter (Figure 1) that illuminates the text page with coloured light permitting the saturation, hue and luminance to vary self-sufficiently.(11,12) The optimum amount of tint required can be matched using the trial-coloured lenses. These lenses do have a property of smoothly varying spectral transmission, minimizing metamerism under various lighting condition. (13) However, the detailed steps of examining with intuitive colorimeter are as follows: (13)

(i) The optimal chromaticity is selected using the Intuitive Colorimeter. At first, 12 different hues are compared. The saturation of the hues that enhance vision is optimized, and the results are compared. Although hue and saturation are alternately changed by small amounts to find the best chromaticity, the eyes remain colour adapted.

(ii) A computer programme is used to determine the best tinted trial lens combination.

(iii) The patient is given the trial lenses and the combination is changed if desired.

(iv) The (calculated) colour prescription is comprised of a series of lenses that is sent to a dyeing company.

(v) To attain the ideal spectral transmission, spectacle lenses are submerged in two dyes.

(vi) A Spectroradiometer and computer software monitors the transmission and then provides the prescribing practitioner and patient with customized details.

(vii) The practitioner visually inspects the colour of the supplied spectacle lenses using trial lenses.


Figure 1: The Intuitive colorimeter


Table 2: Methods of adapting modifications in school environment for MI individuals

Lighting -Turning off fluorescent lights and allowing the child to sit near window or natural light source. -Placing coloured gels over fluorescent lights
Chalkboards -using brown or grey board -Avoiding coloured markers/chalk
Contrast -Avoiding bright coloured papers/cloths that the child wear -Allowing the child to wear a dark brimmed hat to protect from bright light overhead
Computer -Using of coloured overlays to change screen color -Changing the background color of computer to either gray or brown
Reading -Irlen spectral filters and coloured overlays -using magnifying bar/visor/bookstand



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