About Irlen® Syndrome

What is Irlen® Syndrome (IS)?
Irlen® Syndrome (also referred to at times as Meares-Irlen® Syndrome, Scotopic Sensitivity Syndrome, and Visual Stress) is a perceptual processing disorder. It is not an optical problem. It is a problem with the brain’s ability to process visual information.  Please visit the main Irlen® website for more detailed information on Irlen® Syndrome and it's effects on learning, reading and living.

What causes Irlen® Syndrome?
Research shows that these perception problems appear to be caused by a defect in one of the visual pathways that carry messages from the eye to the brain. This defect causes a timing difficulty in the processing of visual information. Irlen® Lenses filter out specific wavelengths of light, which changes the way the brain processes visual information, resulting in the pathway from the eye to the brain functioning normally.

How common is Irlen® Syndrome?
Studies indicate that approximately 12% of the general population has Irlen® Syndrome. Around 50% of children and adults with reading problems have Irlen® Syndrome (IS). For some, IS will be just part of the puzzle, as they may have other learning problems in addition to IS. Using Irlen® Filters will make the page more comfortable to look at by allowing the print to remain clear & stable, thus reducing the strain involved in reading. Sometimes, Irlen® Syndrome is the main problem and the reading problems disappear with Irlen® Filters. Individuals without reading difficulties who suffer from light sensitivity and other visual stress can also be helped.

Has there been research on Irlen® Syndrome?
Yes! Starting with the positive feedback from those wearing Irlen® filters for at least 30 years! Research has shown that Irlen® Syndrome is equally common in males and females. Irlen® Syndrome has been determined to be hereditary, but similar symptoms can also acquired through disease, PTSD, or traumatic brain injury (TBI).  One study of 751 children with IS found that 84% of them had at least one parent who also has Irlen® Syndrome. Please click here to visit the Irlen® for additional research information.

Can everyone with reading problems benefit from Irlen® Spectral Filters?
No. There are children and adults who have other reasons for reading difficulties. The Irlen® screening identifies those who will be able to benefit from this method and the changes can be immediate. These children and adults go on testing to determine their unique and individualized Irlen® Spectral Filters worn as glasses. Please follow this link for detailed information on who we help.

Would colored sunglasses or tinted lenses from an optometrist help?
Not for those with Irlen® Syndrome. What makes Irlen® Spectral Filters so effective is the careful identification of the person's symptoms and the creation of a color that will eliminate them. Only a qualified Irlen® diagnostician can carry out this testing process to determine what color or color combination needs to be worn on each individual.

Meet the diagnostician


Terry Carlson, M. Ed.


Terry Carlson, owner of Irlen® Services Northwest, has a Masters in Special Education/Endorsement in Reading and had been teaching in the public school systems; in secondary Special Education Literacy Programs; for over 20 years. While teaching in the public school system, Terry was introduced to Irlen® overlays by the literacy coach while searching for specific interventions when student’s progress had stalled. She noticed an immediate improvement with reading comprehension. Students often told her, “the words don’t move anymore, I can see the words clearly now.”

Encouraged by the results with her students and realizing their potential once this visual barrier was removed, Terry elected to be trained as an Irlen® Screener in 2008. In 2011, she trained as an Irlen® Diagnostician, which enabled her to administer Irlen® Spectral Filters, as well as train other educators and care givers as Irlen® Screeners. Terry has since retired from the public school system to dedicate her work to identifying and supporting clients who will benefit from the Irlen® Method. Her passion for learning and teaching continues to serve her in this new chapter of her career.

In her free time, Terry enjoys spending time hiking, bicycling, snow shoeing, cross country skiing and relaxing in Eastern Washington with her husband, two boys and grandchildren. Terry enjoys staying physically fit and can often be found at the gym almost every morning. She’s also a voracious reader and loves candy corn.