1834 epilepsy. One stroke participant (subject 2), had reported using a colored overlay and latterly, precision tinted lenses, on a regular basis, since having her stroke a few years prior, although these were not used whilst undertaking the pattern glare test. The pattern glare test is designed to induce visual per- ceptual distortions in susceptible subjects and is now considered to be an established, efﬁcient way to identify individuals with visual stress [6]. It is a simple test, con- sisting of three high-contrast gratings, each subtending 13.63 at the eye when viewed at 40 cm. Each pattern has a duty cycle of 50% with their grating orientation set hori- zontally to mimic text. The ﬁrst pattern has a low spatial frequency (low-SF) of 0.3 cycles per degree (cpd), designed to trigger relatively few distortions and unlikely to have an association with headaches and eyestrain [3]; this ﬁrst pattern, therefore, serves as a useful control for suggestive individuals. The second pattern is designed to elicit maximum distortions, with a mid-spatial frequency (mid-SF) of 2.3 cpd and those who respond adversely to this pattern are likely to experience symptoms of visual stress in their everyday environment. The third high-con- trast grating serves as another control with a higher spatial frequency (high-SF) of 9.4 cpd and it would be expected that this would generate fewer symptoms than the second pattern. The patterns are viewed in succession and the numbers of symptoms generated are summed to give a pattern glare score for each of the gratings. Pattern glare would be suggested if the patient responds with a high score on the mid-SF grating and/or a score with the mid-SF pattern, which is greater that the score with the high-SF grating, the so-called ‘mid-high difference’ variable. This relative, rather than absolute, mid-high difference measure allows for normalization of the subject by accounting for suggestive individuals. Normative values for the pattern glare test have been established [6], taking into account that only a high test score should be regarded as clinically signiﬁcant [34]. The normal range for the mid-SF pattern has been shown as a pattern glare score of \4, and an upper limit of the normal range for the mid-high difference var- iable as being 1. In other words, those with a pattern glare test Score of [3 on the mid-SF grating, or a score of [1 on the mid-high difference variable demonstrate an abnormal degree of pattern glare. The literature also shows that individuals with relatively low visual discomfort are more likely to report distortions with the high-SF than the mid- SF grating; this is attributable to a greater inﬂuence of optical factors when viewing this ﬁner grating rather than symptoms of neurological origin. These individuals are also more likely to report fewer distortions overall [35]. It has been shown that pattern glare scores are similar in males and females. When considering age, younger par- ticipants were found to report more distortions on the mid- 123 J Neurol (2012) 259:1832–1839 SF and the high-SF gratings than older subjects. Overall, with advancing age, there was found to be a greater decrease with the high-SF grating than the mid-SF grating which in turn, results in a small overall increase in the ‘mid-high difference’ variable, although this was not found to be of statistical signiﬁcance. Migraine sufferers were found to score similarly to a control population when viewing each grating in turn, however they were found to score signiﬁcantly higher when considering the mid-high difference variable [6]. All subjects were asked to perform the pattern glare test in line with the developer’s instructions [34]. The subjects were asked to view pattern 1 at 40 cm (low-SF), concen- trating on the central square in the pattern for 5 s. They were then asked to report if any of the following effects were noticed: (1) colors, (2) bending of lines, (3) blurring of lines, (4) shimmering or ﬂickering, (5) fading, (6) shadowy shapes (7) any other effects (to be speciﬁed). The subjects were also asked to specify if any of these effects were more noticeable mainly on the left side, right side or both sides of the pattern. The process was then repeated for pattern 2 (mid-SF) and ﬁnally for pattern 3 (high-SF). The numbers of symptoms reported were then added to give an individual pattern glare score for each of the three patterns. The scores for the high-SF grating were subtracted from the mid-SF grating to determine the mid-high difference variable. Statistical analysis All data were analyzed using the commercially available software (PASW, v. 18, IBM, New York, USA). Data distributions were evaluated using the Kolmogorov–Smir- nov test. A signiﬁcance level of a = 0.05 was used throughout the analysis. Results A summary of the data from the questionnaire and pattern glare test for the stroke and control participants can be seen in Tables 1 and 2, respectively. Data for the mid-SF pattern were found to be normally distributed for the stroke participants (p = 0.579) and also for the control subjects (p = 0.219). For the relative score of the mid-high cpd difference, the data were also normally distributed for the stroke subjects (p = 0.174) as well as the control participants (p = 0.202). Data for the stroke participants’ responses to the high-SF pattern were not found to exhibit a normal distribution (p = 0.045). How- ever, for the control subjects these data were normally distributed (p = 0.271). Statistical analysis of the pattern glare scores (see Table 3; Fig. 1) showed signiﬁcantly higher values for the