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Masking is better than blinding

BMJ 2007; 334 doi: (Published 12 April 2007) Cite this as: BMJ 2007;334:799
  1. Daniel Morris, specialist registrar1,
  2. Scott Fraser, consultant ophthalmologist (,
  3. Richard Wormald, coordinating editor2
  1. 1Sunderland Eye Infirmary
  2. 2Cochrane Eyes and Vision Group, International Centre for Eye Health, London School of Hygiene and Tropical Medicine

    Why the term “blinding” should not be used in clinical trials

    Consider this scenario. An elderly woman has agreed to be part of a clinical trial testing a new drug for age related macular degeneration. Her left eye has very poor vision, and the sight in her previously good right eye is rapidly declining. She is told that she is part of a double blind trial in which she and the doctor will be blinded to the treatment. Taking fright, she withdraws her consent and goes home, terrified that this “blinding” experiment may deprive her of what little vision she has left.

    The term “blinding”—commonly used in clinical trials—is particularly inappropriate in the ophthalmological setting, not least because an outcome measure of a particular trial could indeed be blindness. What an odd situation when the word used to describe trial allocation is also used to describe one of the trial outcomes. As a medical term blindness does not really have a strict definition, but it has a much greater resonance in its sociocultural meaning. This common meaning is emotive enough outside eye care services, but within them the word is rarely used by practitioners and dreaded by patients.

    Although it is …

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