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Correct determination of critical flicker frequency is mandatory when comparisons to other tests are made
  1. Gerald Kircheis1,
  2. Norbert Hilger2,
  3. Dieter Häussinger1
  1. 1 Department of Gastroenterology, Hepatology and Infectious Diseases, Liver Center Düsseldorf, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
  2. 2 Institute of Psychology, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
  1. Correspondence to Dr Gerald Kircheis, Department of Gastroenterology, Hepatology and Infectious Diseases, Heinrich Heine University Düsseldorf, Moorenstrasse 5, Düsseldorf 40225, Germany; kircheis{at}

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Dear Sirs,

There are many situations in daily life where we are exposed to flickering light. This is normally not appreciated because the flicker is so rapid that it is perceived as continuous light. The ability of the human visual system to identify flicker is dependent on the luminance and the chroma of the used stimulating light. The temporal resolution of the human photoreceptors in the central retina, where spatial resolution is optimal, is limited to critical flicker frequencies (CFF) below 50 Hz. Higher CFF values cannot be sensed and therefore are invisible to the naked eye due to the inertia of the human photoreceptors.1

Goldbecker et al 2 compared the four most favoured methods for diagnosing Hepatic Encephalopathy, including CFF. Their results suggest a low diagnostic value of CFF for detection and …

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  • Contributors GK and NH: Conception, design, analysis, interpretation of data and drafting the article. DH: Interpretation of data, critical revision of the article for important intellectual content, and final approval of the version to be published.

  • Competing interests The authors (GK and DH) belong to a group of patent holders for a portable bedside device for critical-flicker-frequency analysis.

  • Ethics approval There was approval by the Ethics Committee of the Medical Faculty of Heinrich Heine University Düsseldorf for all single studies in Hepatic Encephalopathy including CFF measurements.

  • Provenance and peer review Not commissioned; internally peer reviewed.

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