LAUSR

Background The symptom "visual snow" describes the continuous perception of tiny flickering dots within the whole visual field of both eyes. The diagnosis of a visual snow syndrome requires the appearance of typical additional visual symptoms and the exclusion of ophthalmological or neurological causes, or pharmacological influences. Patients and Methods Three male and four female subjects between 13 and 36 years of age referred with visual snow were investigated and asked about their symptoms. A complete ophthalmological investigation, including binocular fundoscopy, was performed in all patients. Furthermore, best corrected visual acuity, perimetry, binocular functions, colour vision (D15-test), full-field ERG, pattern-reversal VEP and SD-OCT images of macula and optic nerve (RNFL) were analysed. Results Visual acuity of at least 1.0 and normal findings for all further investigations were observed in all patients. The following additional visual symptoms were identified: illusionary palinopsia (n = 6), disturbance of night vision (n = 5), positive light phenomena (n = 7). A history of migraine with aura was reported in five patients. The intake of hallucinogenic drugs or centrally active pharmaceuticals was denied by all patients. The findings of available or initiated neurological investigations were normal. Conclusions The visual snow syndrome has to be regarded as a diagnosis of exclusion. Visual function parameters are not impaired. Apart from eye diseases, a persistent migraine aura as well as neurological diseases or the intake of hallucinogenic drugs must be excluded as possible causes of visual snow and palinopsia.