J Neurol (2012) 259:1832–1839 DOI 10.1007/s00415-012-6418-5 O R I G I N A L C O M M U N I C A T I O N Susceptibility to pattern glare following stroke Ian G. Beasley • Leon N. Davies Received: 1 December 2011 / Revised: 9 January 2012 / Accepted: 10 January 2012 / Published online: 31 January 2012 The Author(s) 2012. This article is published with open access at Springerlink.com Abstract The aim of this work was to measure suscep- tibility 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 sus- ceptibility was undertaken using the pattern glare test. An abnormal degree of pattern glare is present when individ- uals 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 explana- tion for the perceptual distortions experienced by individ- uals susceptible to pattern glare. Further work to assess the I. G. Beasley L. N. Davies (&) Ophthalmic Research Group, Life and Health Sciences, Aston University, Birmingham B4 7ET, UK e-mail: l.n.davies@aston.ac.uk L. N. Davies Aston Research Centre for Healthy Ageing (ARCHA), Aston University, Birmingham, UK 123 beneﬁts of spectral ﬁlters in reducing perceptual distortions in stroke patients is currently underway. Keywords Stroke Pattern glare Cortical hyperexcitability 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 symptoms that arise from pattern glare susceptibility, resulting in visual stress, are often referred to by their historically derived terms, Meares–Irlen syndrome and scotopic sensitivity syndrome [5] and more recently referred to by the acronym MISViS, which denotes the title Meares–Irlen syndrome/visual stress [6]. The characteristics of the visual stimulus, which cause (or at least contribute in generating visual stress) is sensory in origin [7] and therefore distinguishable from factors of motor origin, such as oculomotor balance, bin- ocular vergence, and accommodation [8]. The visual per- ceptual distortions that are generated by susceptibility to pattern glare is maximal when the spatial frequency of the stimulus is around three cycles per degree, with a pattern of even width and spacing, high contrast and viewed binoc- ularly [1, 2]. Many of the attributes necessary to generate