Clinical Trial: Visual Discomfort and Reading

Study Status: Completed
Recruit Status: Completed
Study Type: Observational

Official Title: Visual Discomfort and Reading

Brief Summary: Reading can be an uncomfortable and difficult task for some people. Symptoms include unpleasant somatic and perceptual effects, such as eye-strain, headache, and blurred text, despite normal visual acuity. This condition has been called Visual Discomfort, but little is known about the symptoms and frequency of reading problems associated with this disorder. Several studies have proposed that Visual Discomfort is caused by increased noise in the visual system due to spreading cortical activation across different spatial frequency channels. This study examines the prevalence and severity of visual discomfort in a college student population and tests the noisy visual system hypothesis.

Detailed Summary:

Wilkins et al (1980) found that paroxysmal activity in photosensitive epileptic patients can be triggered by binocular viewing of a large repetitive striped pattern with a spatial frequency of 1-4 cycles deg-1, a contrast of 10% or more, and a duty cycle of 50%. Sensitivity to this visual pattern varies in the non-epileptic population (Wilkins et al, 1984) but can produce unpleasant somatic (e.g., eye-strain, headache) and perceptual effects (e.g., flicker, color illusions). This condition has been termed visual discomfort (Wilkins et al., 1984) or visual stress (Wilkins, 1995).

Reading can be especially difficult for those with visual discomfort because most printed text is a repetitive striped pattern with the same characteristics that cause visual discomfort; that is, spatial frequencies between 1-6 cycles deg-1 (Legge et al., 1985), high contrast, and 50% duty cycle (Wilkins & Nimmo-Smith, 1984; 1987). Those with visual discomfort report a variety of symptoms when they read, such as, movement of print, blurring, letter distortion (size, doubling, fading or darkening), patterns appearing in white spaces, color illusions as letter highlights or moving blobs, nausea, dizziness, headache, eye-strain, and glare discomfort (Wilkins, 2003). One study (Wilkins & Nimmo-Smith, 1987) found that decreasing the duty cycle (double or triple spacing the lines of text) was sufficient to reduce or eliminate most of the unpleasant symptoms.

Symptom frequency while reading appears to vary with a person's sensitivity to the striped pattern (Conlon et al., 1998) and is more common among those who suffer from headaches or migraines (Wilkins et al, 1984; Conlon et al., 1999). Effective reading time is considerably reduced by visual discomfort symptoms (Conlon et al, 1998; Conlon et al, 1999, Wilkins, 2003). Most college students with
Sponsor: Southern California College of Optometry

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Information By: Southern California College of Optometry

Dates:
Date Received: November 17, 2006
Date Started: July 2004
Date Completion:
Last Updated: November 11, 2009
Last Verified: January 2009