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Use of Visual Search in the Assessment of Pattern-Related Visual Stress (PRVS) and Its Alleviation by Colored Filters

¹From the Myopia and Visual Function Group, Department of Optometry and Ophthalmic Dispensing, Anglia Ruskin University, Cambridge, United Kingdom; and the ²School of Optometry and Vision Science, University of Bradford, Bradford, United Kingdom.

PURPOSE. Visual search measures have been used to evaluate the effects of pattern-related visual stress (PRVS), and its alleviation by colored filters, but tasks and results have varied between studies. Performance on a high-difficulty search task was measured in individuals having low- and high-PRVS susceptibility.

METHODS. Two PRVS groups (low and high) were formed on the basis of participants’ responses to a visual symptoms questionnaire and perceptions of a high-contrast grating pattern. Each participant searched for multiple instances of a single-digit number (target) within an array of similar numbers (distractors). Performance was measured by response time and error count. A three-factor, mixed-factorial ANOVA design was used to investigate the effects of PRVS group, a high-contrast background PATTERN, an overlay of an individually-selected COLOR.

RESULTS. Individuals classified with high visual stress were found to experience significantly greater improvement in reading performance (F_(1,26) = 24.579, P < 0.001) and reduction in the number of errors (F_(1,26) = 9.502, P = 0.005) when performing the Wilkins Rate of Reading Test with a colored overlay than those with low visual stress. Error count was significantly higher in the high-PRVS group, when subjects were performing a visual search task, in the absence of either PATTERN or COLOR, but response time was not significantly different. Neither response time nor error count was significantly affected by background PATTERN and/or colored overlay.

CONCLUSIONS. Results of this and previous studies confirm that visual search measures may be helpful in the assessment of PRVS, but several important methodological issues may limit their application in this context.