A MAGNETOENCEPHALOGRAPHIC INVESTIGATION OF VISUAL INFORMATION PROCESSING IN

IRLEN’S SCOTOPIC SENSITIVITY SYNDROME

by Jeffrey David Lewine, Ph.D, John Davis, Ph.D., Sherri Provencal, M.A.,

James Edgar, M.A., and William Orrison, Jr., M.D.

Conducted at The Center for Advanced Medical Technologies, The University of Utah School of Medicine,

Salt Lake City, Utah, and Department of Psychology, The University of New Mexico, Albuquerque, New Mexico

Many persons with poor reading skills and habits demonstrate significant visual fatigue and discomfort when

observing high contrast, high luminance stimuli. Dizziness, headaches, strain or fatigue are some of the

ancillary findings in Scotopic Sensitivity/Irlen Syndrome (SSS) that compound reading difficulties. Under high

luminance conditions, words distort. They may float above the page or jumble into a wavy, incomprehensible

tangle. The background may pulsate or eradicate parts of letters. Several behavioral studies demonstrate that

many of the deleterious aspects of the condition can be alleviated by wearing colored Irlen lenses, the best color

being different for each patient.

At present, the relevant physiological mechanisms are unknown; but presumably they are related to altered

visual information processing. In this study, magnetoencephalography (MEG) was used to characterize visual

responses in conditions with and without lenses. Steady-state visual evoked magnetic fields were recorded from

8 subjects with SSS and 8 normal control subjects using a 122-channel, whole-head biomagnetometer. During

the testing, subjects fixated the center of a 4 square checker board that contrast reversed every 200 msec. There

was a small black circle at fixation that briefly flashed white every 1-2 seconds, and subjects were instructed to

count flashes.

For the SSS group, each subject was evaluated with and without custom colored Irlen lenses. Control subjects

were tested without lenses and with a lens pair that caused the maximum change in luminance. In all cases, the

evoked magnetic signal reflected a complicated pattern of bilateral activation of multiple cortical generators. A

major difference in with and without lens conditions was seen between 170 and 200 msec post-stimulus.

For normal subjects, without lenses, the field pattern at this time was mostly dipolar and reflected midline

calcarine activity. When lenses were on, the pattern was much more complex, reflecting multiple generators.

The reverse situation was seen for 6 or 8 subjects with SSS. That is, a complex field pattern was seen without

lenses, whereas an organized dipolar pattern was seen with lenses.

Note: Sorry, but I could not get the formatting  resolved.  Roger Wheaton