Susceptibility to pattern glare following stroke

Ian G Beasley,Leon N Davies

doi:10.1007/s00415-012-6418-5

Abstract

The aim of this work was to measure susceptibility to pattern glare within a stroke group, employing a direct method of assessment. Twenty stroke subjects, aged 38–85 years, were recruited, along with an age-matched control group (n = 20). Assessment of pattern glare susceptibility was undertaken using the pattern glare test. An abnormal degree of pattern glare is present when individuals score >1 on the mid-high spatial frequency difference variable, a relative score that allows for normalization of the subject, or >3 when viewing the mid spatial frequency grating. Stroke subjects demonstrate elevated levels of pattern glare compared to normative data values and a control population, as determined using the pattern glare test. This was most notable when considering the output measure for the mid-high difference variable. The mean score for the mid-high difference variable was 2.15 SD 1.27 for the stroke subjects versus 0.10 SD 1.12 for the control subjects. When considering the mid-high difference variable, 75% of the stroke group recorded an abnormal level of pattern glare compared to 5% in the control group. This study demonstrates an association between stroke subjects and elevated levels of pattern glare. Cortical hyperexcitability has been shown to present following stroke, and this has been proposed as a plausible explanation for the perceptual distortions experienced by individuals susceptible to pattern glare. Further work to assess the benefits of spectral filters in reducing perceptual distortions in stroke patients is currently underway.

Highlights

Ocular discomfort often manifests when viewing certain image types, such as repetitive striped patterns [1]
This study demonstrates an association between stroke subjects and elevated levels of pattern glare
The present study has demonstrated that stroke subjects respond with significantly higher pattern glare scores than a control population when undertaking the pattern glare test; this elevation in scores being most notable for the mid-high difference variable, a relative score that allows for normalization of the subject by taking into account suggestibility

Summary

Introduction

Ocular discomfort often manifests when viewing certain image types, such as repetitive striped patterns [1] The intensity of these effects will vary according to individual susceptibility and the precise nature of the pattern, most notably, its spatial frequency and contrast level [2]. An adverse response when viewing stimuli of this type, i.e., striped patterns, has been termed ‘patterned glare’ [3] and latterly ‘pattern glare’ [4] For susceptible individuals, this can result in visual stress, giving rise to symptoms of eyestrain, headaches and glare, along with illusions of colors, shapes, and motion [3]. The spatial frequency of this alternating high contrast pattern, formed by text, has been shown to fall within the range known to generate pattern glare symptoms [11]. The origins of pattern glare and visual stress are equivocal, it is thought that these effects arise due to cortical hyper-excitability [2, 7, 12,13,14]

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