Abstract
Background and Purpose: Visual Snow (VS) is a disorder characterised by the subjective perception of black-and-white visual static. The aetiology of this condition is not known. In our previous work we suggested that there is a link between short-wave (S or “blue” cone) signals and severity of visual snow symptoms. Therefore we aimed to further characterise this potential link.Methods: Patients (n = 22) with classic VS based on the diagnostic criteria and healthy controls (n = 12), underwent Intuitive Colorimetry (IC) testing (Cerium Visual Technologies). Twelve hue directions (expressed as angle in CIE 1976 LUV space relative to D65) were rated on a five-point scale from preferred (relieving, positive score) to non-preferred (exacerbating, negative score), and overall preferred and non-preferred angles were chosen.Results: A non-preferred violet region near the tritanopic confusion line / S-cone axis (267 deg.) was strongly associated with exacerbation of VS symptoms (range 250–310 deg, mean 276 ± 16, n = 20, Rayleigh p < 0.001). Two subjects with non-preferred region > 90 deg from mean were considered as outliers. Median rank at hue angle 270 deg was significantly lower than at angle 90 (−1.5 vs. 0.0, p < 0.001, Wilcoxon non-parametric rank-sum test). Patients showed preference for one of two spectral regions which relieved VS symptoms: orange-yellow (range 50–110 deg., mean 79 ± 24, n = 14) and turquoise-blue (range (210–250 deg., mean 234 ± 27, n = 8).Conclusion: Our results show that visual snow symptoms are exacerbated by colour modulation that selectively increased levels of S-cone excitation. Because S-cone signals travel on primordial brain pathways that regulate cortical rhythms (koniocellular pathways) we hypothesis that these pathways contribute to the pathogenesis of this disorder.
Highlights
Visual Snow (VS) refers to the persistent visual experience of static in the whole visual field of both eyes likened to “static analogue television noise” [1] and was originally reported as a positive visual phenomena experienced by patients with migraine [2]
It is clear from all these studies that VS and visual snow syndrome (VSS) exists as a continuum and the frequency of associated non-visual symptoms often carries a higher symptom severity and burden of disease [5, 9, 10]
The VS cohort consisted of 9 female and 13 male patients with a mean age of 31.8 ± 11.3 years
Summary
Visual Snow (VS) refers to the persistent visual experience of static in the whole visual field of both eyes likened to “static analogue television noise” [1] and was originally reported as a positive visual phenomena experienced by patients with migraine [2]. The visual snow syndrome (VSS) is classified based on a set of diagnostic criteria which capture the spectrum of pathology of this condition [3, 4]. Their study confirmed several aspects of VSS that had previously been characterised in smaller cohorts including the lack of gender prevalence, onset early in life and absence of relationship to prior psychotropic substance use [6,7,8] It is clear from all these studies that VS and VSS exists as a continuum and the frequency of associated non-visual symptoms often carries a higher symptom severity and burden of disease [5, 9, 10].
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