How Contrast Sensitivity Affects Learning | Irlen SyndromeTo read well your eyes must work well. Unfortunately most people think this means if text looks blurry, you need an eye exam. The truth is, there is more that goes on with eye function than just visual acuity. This is why it is very important to have your child examined by a board certified BEHAVIORAL optometrist, not just a regular optometrist.

But even then, there is a syndrome that some optometrists may not check for, where the eye is sensitive to the contrast of a pure black on a white background. It is a bit like blue on red for the rest of us. Try to read the following sentence, and see how it is hard to read and may even hurt your eyes. This is an example of what contrast sensitivity could be like.

For me the red on blue text is very hard to read. Some people have the same difficulty with black text on a white background. If your child complains of “the text moving around” on the page, or that the white on the page hurts the eyes, that may be the reason.

One of the most important elements of processing that happens in the eye is to look for shapes and the edges of shapes. There are around 100 million rods and cones in each retina and only 1 million neurons in each optic nerve. So the eye is aggregating the individual rods and cones and it is in the aggregating process that the eye is very sensitive to changes in intensity.

If it is too sensitive to a black/white contrast, you will get this effect, known as contrast sensitivity. It is also called Scotopic Sensitivity or Irlen Syndrome, after Helen Irlen who first discovered it in the 1980’s.

Key Symptoms of Contrast Sensitivity

  • Sensitivity to strong sunlight and fluorescent lights
  • Complaining about the text moving
  • Complaining about distortions of the page
  • Finding larger text easier (this can be related to eye-tracking too)
  • Eyes watering while staring at computer screens
  • Getting headaches while trying to read or do mathematics
  • Prefers to read in dim light
  • Gets tired quickly when reading

Keep in mind that all these symptoms could also be related to a visual processing issue, so a child should be checked by a behavioral optometrist, as well as screened for Irlen Syndrome, if it is not obvious which problem may be involved. Also, the symptoms could be related to location. For example, if a child tends to do worse with schoolwork at school but does fine at home, it could be the fluorescent lighting at school that is effecting him or her.

How Reading is Effected by Contrast Sensitivity

A child who had this visual issue may not realize they do not see letters on the page as most people do. Often they will see distortions on the page which make it almost impossible to focus and read individual words. Here are some examples of those distortions:

Copyright 1987 by Perceptual Development Corp/Helen Irlen. All rights reserved.

The Solution To Contrast Sensitivity

If you feel that your child may be suffering from this issue, it is essential to get an Irlen screening done. As part of the screening processing, color overlays are chosen to eliminate distortions and provide immediate relief from the symptoms. If you feel your child may be having contrast issues, please contact me and we can decide if your child needs to be screened for Irlen Syndrome.

Once the screening is done, if contrast sensitivity is found, then the child would be referred to a specialist who can assist in creating tinted glasses which can rectify the contrast sensitivity in all situations.


Bonnie Landau
Bonnie Landau
Bonnie Landau is a special education advocate and educational consultant in Ventura County, California. Her goal is to help parents find strategies and solutions to help their children succeed in school and in life. Bonnie is the author of Special Ed Mom Survival Guide: How to Prevail in the Special Education Process and Find Life-long Strategies for You and Your Child.