Use of visual search in the assessment of pattern-related visual stress (PRVS) and its alleviation by coloured filters
Peter M. Allen 1*,
James M. Gilchrist 2,
and
Jarrod Hollis 1
1 Department of Optometry and Ophthalmic Dispensing, Anglia Ruskin University, Cambridge, United Kingdom
2 Department of Optometry, University of Bradford, Bradford, United Kingdom
* To whom correspondence should be addressed. E-mail: peter.allen{at}anglia.ac.uk.
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Abstract |
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Purpose: Visual search measures have been used to evaluate the effects of pattern-related visual stress (PRVS), and its alleviation by coloured filters, but tasks and results have varied between studies. We measure performance with a high-difficulty search task in individuals having low- and high-PRVS susceptibility.
Methods: Two PRVS groups (low & 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 3-factor mixed factorial ANOVA design was employed to investigate the effects of: i) PRVS GROUP, ii) a high-contrast background PATTERN, iii) an overlay of an individually-selected COLOUR.
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 using a coloured overlay than those with low visual stress. When performing a visual search task Error Count was significantly higher in the high-PRVS group in the absence of either PATTERN or COLOUR, but Response Time was not significantly different. Neither Response Time nor Error Count was significantly affected by background PATTERN and/or COLOURed overlay.
Conclusions: Results of this and previous studies confirm that visual search measures may be helpful in the assessment of PRVS, but a number of important methodological issues may limit their application in this context.
Key Words:
visual search, visual stress, coloured overlays
