Neuro-ophthalmologic Findings in Visual Snow Syndrome

Abstract

Background and Purpose The findings of ophthalmic examinations have not been systematically investigated in visual snow syndrome. This study reviewed the abnormal neuroophthalmologic findings in a patient cohort with symptoms of visual snow syndrome. Methods We retrospectively reviewed 28 patients who were referred for symptoms of visual snow to a tertiary referral hospital from November 2016 to October 2019. We defined the findings of best corrected visual acuity (BCVA), visual field testing, pupillary light reflex, contrast sensitivity, full-field and multifocal electroretinography, and optical coherence tomography. Results Twenty patients (71%) were finally diagnosed as visual snow syndrome. Their additional visual symptoms included illusionary palinopsia (61%), enhanced entoptic phenomenon (65%), disturbance of night vision (44%), and photophobia (65%). A history of migraine was identified in ten patients (50%). The mean BCVA was less than 0.1 logarithm of the minimum angle of resolution, and electrophysiology showed normal retinal function in all patients. Contrast sensitivity was decreased in two of the seven patients tested. Medical treatment was applied to five patients which all turned out to be ineffective. Among the eight patients who were excluded, one was diagnosed with rod-cone dystrophy and another with idiopathic intracranial hypertension. Conclusions Neuro-ophthalmologic findings are mostly normal in patients with visual snow syndrome. Retinal or neurological diseases must be excluded as possible causes of visual snow.

Visual Snow Syndrome as a Network Disorder: A Systematic Review

“…Ophthalmological or radiological routine findings are without pathological findings in most cases ( 4 , 11 , 16 , 17 , 39 ). There are some case reports of patients with positive visual phenomena similar to those in VS, which turned out to be caused by ocular pathology, such as birdshot retinopathia ( 16 , 40 ), but also diseases leading to an extensive visual impairment like in a patient described by Mehta et al who had advanced macular atrophy with cystic retinal degeneration and developed Charles-Bonnet syndrome with VS in addition ( 16 ).…”

“…Several studies have collected data on the prevalence of symptoms in groups of patients with VSS or VS, either in online surveys ( 4 , 11 , 12 ) or in interviews at headache centers or neuro-ophthalmologic departments ( 4 , 13 – 17 ). Per definition, patients with VS experience a visual static, similar to the flickering of an old TV, with many, moving colored or black-and-white dots in the entire visual field.…”

“…There are single case reports of a decrease in symptom severity after the use of mydriatics ( 53 ) and a remission under amitriptyline ( 54 ). Antipsychotic drugs ( 55 ), glucocorticoids, beta-blocker, acetazolamide ( 17 ), other antidepressants ( 56 ) and antiseizure medications, benzodiazepines, migraine prophylaxis, and even ketamine were tried with a few cases of partial improvement, but mostly no benefit ( 16 ).…”

“…Three groups examined visual perception thresholds in VSS patients demonstrating decreased spatial contrast sensitivity ( 17 ), reduced center-surround contrast suppression, elevated luminance increment thresholds on a textured background ( 58 ), and significantly more difficulties recognizing image orientations specifically at a flickering frequency of 15 Hz ( 59 ).…”

“…In another study, VS patients showed normal color and rapid flicker sensitivity but a delayed dilatation after the initial constriction of the pupil after the presentation of a chromatic stimulus ( 60 ). The latter could indicate a longer afferent stimulus persistence ( 60 ) or an autonomic dysregulation ( 17 ). A limitation of this study ( 60 ) was the small number of patients and controls included.…”