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Correctness is mandatory in science: response to ‘correct determination of Critical Flicker Frequency is mandatory when comparisons to other tests are made’
  1. Anita Blanka Tryc1,2,
  2. Karin Weissenborn1,2
  1. 1 Integrated Research and Treatment Center Transplantation (IFB-Tx), Hannover, Germany
  2. 2 Clinic for Neurology and Neurophysiology, Hannover Medical School, Hannover, Germany
  1. Correspondence to Dr Anita Blanka Tryc, Hannover Medical School, Clinic for Neurology and Neurophysiology, Hannover 30623, Germany; tryc.anita{at}

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Kircheis and coauthors suggest ‘inadequate handling of the test’ as reason for the worse sensitivity of the Critical Flicker Frequency (CFF) for diagnosing hepatic encephalopathy (HE) compared with other methods evaluated in our study.1 ,2 Their main criticism aims at our finding of CFF above 50 Hz in healthy controls. They argue that flicker frequencies above 50 Hz ‘cannot be sensed and therefore are invisible for the naked eye …’ referring to a review by Shady et al 3 In fact, Shady et al do not give a clear cut-off at 50 Hz but indicate that ‘… the temporal resolution of a typical observer is limited to a CFF of ≈50 for luminance flicker’. CFF depends on several parameters, such as luminance, wavelength and luminous intensity. In everyday life, the experience of CFF thresholds above …

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  • Contributors ABT and KW wrote the manuscript.

  • Competing interests None.

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

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