The authors present a case series of individuals referred to an electroretinography (ERG) lab for assessment due to abnormal vision symptoms, over a two year period. Cases with visual snow syndrome (VSS) or isolated visual snow (VS) were included. All other ocular pathology were excluded. Of 11 potential cases, eight were included. The following data was extracted from medical records: demographics, medical history, visual acuity, stereoacuity, perimetry, colour vision, OCT and brain imaging. ERG using the standard protocol of the International Society for Clinical Electrophysiology of Vision was performed. An age and sex matched control group was identified for comparison of the full field ERG and visually evoked potentials (VEP). Of the cases identified seven were VSS and one VS. Fifty percent were female and the mean age was 24 years. All cases had good visual acuity, stereoacuity and a normal OCT, perimetry and MRI. Three quarters had received a diagnosis of a mental health disorder. Migraine had also been diagnosed in 75%. No significant difference was noted between individuals with VS and controls on VEP. On full field ERG however, individuals with VS had a mean b-wave and flicker wave amplitude (light-adapted, 3.0 stimuli) that was greater than controls in the right eye. Mean b-wave amplitude (dark adapted, 10.0 stimuli) was significantly different in the left eye on removal of outliers. Despite this study being small and retrospective it has highlighted areas of retinal signal processing which are abnormal in individuals with VS for the focus of future studies.
A case series of electroretinography findings in visual snow syndrome
Reviewed by Lauren Hepworth
Analysis of retinal structure and electrophysiological function in visual snow syndrome: an exploratory case series.
CONTRIBUTOR
Lauren R Hepworth
University of Liverpool; Honorary Stroke Specialist Clinical Orthoptist, Northern Care Alliance NHS Foundation Trust; St Helen’s and Knowsley NHS Foundation Trust, UK.
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