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Hereford Independent School District

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Response to Intervention (RTI)/Multi-Tiered System of Support (MTSS) » Irlen Syndrome (Sensory Processing Deficit)

Irlen Syndrome (Sensory Processing Deficit)

Irlen Syndrome

(or Sensory Processing Deficit)


  • A problem with the brain's ability to process visual information. This difficulty is associated with light induced visual perceptual difficulties. 
  • Scotopic Sensitivity Syndrome is not associated with visual acuity (glasses or contacts) or intelligence; it is a neurological problem. 
  • This syndrome may affect performance in reading, math, writing, behavior, attention and concentration. 
  • Scotopic Sensitivity can cause discomfort such as headaches, migraines, severe fatigue, light sensitivity, depth perception and other environmental issues. 
  • Factors of Scotopic Sensitivity Syndrome 
  1. Light sensitivity
  2. Inadequate background accommodation
  3. Poor print resolution
  4. Restricted span of recognition
  5. Lack of sustained attention


  • Things to watch for in the classroom:
  1. Students report that the letters or words are moving or “falling off the page”.
  2. Students say that the background of the page is bright, uncomfortable, flashing or twinkling.
  3. Their reading is slow and inefficient.
  4. They are unable to do continuous reading..
  5. The student may tire or fall asleep while reading.
  6. The student may experience reading-induced headaches or nausea.



Be sure to rule out vision problems before referring for Scotopic Sensitivity screening.