Abstract

Volume.125 Number.4

Original article : Clinical science

Clinical Characteristics of Visual Snow Syndrome in 21 Japanese Patients
Mizuho Mitsuhata1, Masato Wakakura1, Mayumi Iwasa1, Akiko Yamagami1, Kenji Inoue1, Yukihisa Suzuki2,3, Kenji Ishii3
1 Inouye Eye Hospital
2 Department of Ophthalmology, Japan Community Health care Organization Mishima General Hospital
3 Team for Neuroimaging Research, Tokyo Metropolitan Institute of Gerontology

Purpose: Since 2005, we have been accumulating cases involving complaints of innumerable small dots persistently appearing throughout the visual field and other such phenomena. In the recent years, similar cases of snow noise have been reported as "visual snow syndrome (VSS)". We report 21 cases examined by us to compare our cases with those previously reported as VSS.
Methods: We retrospectively collected data on sex, age at initial visit, age at onset, subjective symptoms, backgrounds, ophthalmologic findings, course, therapeutic details, factors associated with remission and exacerbation, and outcomes of the visual phenomenon related to the patients in 21 cases. These data were compared with the diagnostic criteria reported by Shankin et al. Moreover, 18F-fluorodeoxy glucose positron emission tomography (FDG-PET) results corresponding to 6 cases were examined.
Results: We included 9 male and 12 female patients. Mean age at onset was 27.3±13.2 years. Regarding subjective symptoms other than continuous snow noise (visual snow), palinopsia in 17 of 20 cases (85.0%), exacerbation of entoptic phenomenon in 12 of 12 cases (100%), and photophobia in 9 of 11 cases (81.8%) were observed. A history of migraines was noted in 12 of the 21 cases (57.1%), and self-history or family history of migraines was observed in 18 of the 21 cases (85.7%). Complete agreement was obtained between 17 of the 21 present cases (81.0%) and the diagnostic criteria reported by Schankin, et al previously. FDG-PET examinations showed hypometabolism in the visual association cortex in 4 of the 6 cases (66.7%).
Conclusions: The clinical manifestations in the 21 Japanese cases included in this study were similar to those of the previously reported overseas VSS cases. Although this visual phenomenon impacts daily life, ophthalmologists often regard it as a psychogenic disorder caused by the lack of knowledge on this syndrome. VSS is not rare; therefore, ophthalmologists should have a better awareness of this condition.
Nippon Ganka Gakkai Zasshi (J Jpn Ophthalmol Soc) 125: 438-445, 2021.

Key words
Visual snow syndrome, Snow noise, Migraine, Persistent visual positive phenomenon, 18F-fluorodeoxy glucose positron emission tomography
Reprint requests to
Mizuho Mitsuhata, M. D. Inouye Eye Hospital. 4-3 Kandasurugadai, Chiyoda-ku, Tokyo 101-0062, Japan