Reducing visual stress for the dyslexic learner with coloured overlays

Criona Leahy Optometrist performs a coloured overlay assessment for dyslexic readers on a Cerium machine
Of the school population experience distortion, discomfort or visual stress while reading
Of those suffering from these symptoms may benefit from coloured overlays
Of an increase in reading rate is shown for those that benefit from coloured overlays
The problem for dyslexic readers

Visual stress & discomfort experienced by dyslexic readers varies but can include:

  • Movement or merging of print
  • Fatigue while reading
  • Losing the line
  • Seeing patterns within the print
  • Blurring, fading, flickering of the print
  • Changing shapes of letters or words
  • Jumping, doubling or skipping of print

These symptoms fall into visual stress, visual dyslexia or scotopic sensitivity syndrome. 

How coloured overlays can help dyslexic readers

In many cases the symptoms experience by dyslexic readers may be remedied by reading through coloured overlays that filter out certain wavelengths of light.

This is done by placing coloured plastic overlayed on the print.

Coloured Overlays

Not everyone is comfortable with black & white text.

If you filter out the light wavelength that dyslexic readers are sensitive to, the visual stress is reduced & the rate of reading improves.

Colorimetry exam being performed by Optometrist Criona Leahy


For each individual, there is a specific hue (colour) & saturation (strength) that will work best.

Colorimetry will strive to identify the precise colour that is most effective in reducing the visual stress & increase the reading speed & comfort.

Criona Leahy Optometrist selecting a coloured overlay to help dyslexic readers

Coloured Overlay Assessment

A Coloured Overlay assessment takes up to 1 hour.

It is not an eye examination & anyone over the age of 7 is suitable.

What’s involved in a Coloured Overlay Assessment

History of Symptoms
Vision Testing
Muscle Balance
Eye Dominance
Rate of Reading Test
Pattern Glare Test
Coloured Overlays
Coloured overlay assessment for dyslexic readers suffering from visual stress
“5% of children in mainstream education read at least 25% more quickly with an overlay”
Professor Arnold Wilkins
Coloured overlays & their effects on reading speed (2002)
Years experience

Close up shot of the Cerium logo on coloured overlay assessment machine

Criona Leahy

I’m a qualified Optometrist since 1990, registered with CORU. I’ve practiced in private practice, in large multiples & I’ve taught Optometry students in TUD for over 12 years.

I know firsthand that routine eye examinations do not cater for the symptoms experienced by the dyslexic learner when reading.

I’ve a special interest in Visual Stress experienced by dyslexic learners & I’m passionate about the benefits of coloured overlays.

Consultation prices

Coloured Overlay Consultations & Costs



One hour sessions

  • Available 11am to 3:30pm
  • Contact to book
  • 15 Baggot Street Upper, Dublin 4



Per one hour session

  • One session required
  • Qualified Optometrist
  • 30+ years experience

Coloured Overlays


Per coloured overlay

  • Easy to use
  • Reduces visual stress
  • Can improve rate of reading by 25%