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C. Chase, W.H. Ridder, III, E. Borsting; Visual Discomfort and Reading . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4591.
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Purpose: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 examined the prevalence and severity of visual discomfort in a college student population and tested the noisy visual system hypothesis. Methods: Conlon's (1999) survey of visual discomfort symptoms was administered to 130 randomly recruited college students. Results showed a bimodal distribution with 21% of the student 1 s.d. above the mean. 35% of the high discomfort group reported having to frequently re–read text; 38% said they were almost always reading slowly because of their discomfort symptoms; and 34% said bright lighting conditions were almost always disruptive. 14 students with high discomfort were compared to 14 with low discomfort on reading skills and verbal fluency. Detection thresholds and point of subjective equality on a speed judgment task also were made using cone–isolating stimuli to estimate L/M ratios. Results: There were no significant differences between the groups in their reading skills or verbal fluency under viewing conditions that minimize visual symptoms. The low discomfort group had a modest correlation (R2 = .28) and slope = .38 between detection L/M ratios and speed judgment L/M ratios. Their group average L/M ratio decreased from 2.5 for detection to 2.0 for speed judgment. The high discomfort group had a very high correlation (R2 = .91) and a slope = 1.35. Their group average L/M ratio remained steady at 2.0 for both detection and speed judgment. Conclusions: Visual discomfort during reading is a significant problem in a college student population. These symptoms are not the result of poor reading or verbal fluency skills. High visual discomfort students maintained strong L/M–cone ratio correlations between stimulus detection and speed judgment thresholds, suggesting L– and M–cone signal strengths remained relatively constant in their visual systems. These results are inconsistent with the noisy visual system hypothesis of visual discomfort.
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