Abstract
Objective: To confirm the presence of visual snow syndrome (VS) in the individual patient. We tested the hypothesis that patients with VS have an increased threshold for detecting visual contrasts.
Background: Patients with VS suffer from a continuous TV snow-like visual disturbance in the entire visual field that might reduce the contrast perceived. Currently, the only objective measure is hypermetabolism of the lingual gyrus found at the group level. In clinical practice, however, individual patients present with subjective symptoms, and objective measures are lacking to confirm the diagnosis.
Design/Methods: Twenty patients with VS were compared to 20 age-, gender-, migraine- and aura-matched controls. Subjects were randomly presented vertically left or right tilted bars flickering at six different frequencies (15Hz, 20Hz, 25Hz, 30Hz, 35Hz, 40Hz). The contrast threshold was measured in a two-alternative adaptive forced-choice procedure (QUEST) for the discrimination between the two image orientations. The threshold was defined as the log10 (Michelson-Contrast) necessary to achieve the correct response in 75% of the cases.
Results: The 75% contrast threshold at 15 Hz was significantly higher in VS patients compared to controls (0.601 Wilks-Lambda p=0.007; −1.94±0.13 vs. −2.26±0.37, T=−3.71, p=0.001, MANOVA). The AUC for the ROC curve of 75% contrast threshold at 15 Hz was 0.73±0.09. A contrast threshold of −2,00 is able to support the diagnosis of VS in an individual patient with a sensitivity of 80% and a specificity of 70%.
Conclusions: The visual 75% contrast threshold measured at 15 Hz is the first technical test that might be able to confirm the hitherto purely subjective and history-driven diagnosis of VS in an individual patient.
Disclosure: Dr. Eren has nothing to disclose. Dr. Eggert has nothing to disclose. Dr. Ruscheweyh has nothing to disclose. Dr. Straube has nothing to disclose. Dr. Schankin has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Novartis Pharmaceuticals, Almirall, Eli Lilly, and Allergan.
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