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Follicle size in trachoma: assessment of a well-known trachoma grading diagram
  1. Daniel P Morberg1,
  2. Abdou Amza2,3,
  3. Sintayehu Gebresillasie4,
  4. Zerihun Tadesse4,
  5. Sun N Yu1,
  6. Nicole E Stoller1,
  7. Paul M Emerson5,
  8. Bruce D Gaynor1,6,
  9. Thomas M Lietman1,6,7,8,
  10. Jeremy D Keenan1,6
  1. 1 Francis I. Proctor Foundation, University of California, San Francisco, USA
  2. 2 Faculté des Sciences de la Santé, Université Abdou Moumouni de Niamey, Niamey, Niger
  3. 3 Programme National de Santé Oculaire, Niamey, Niger
  4. 4 The Carter Center Ethiopia, Addis Ababa, Ethiopia
  5. 5 The Carter Center, Atlanta, USA
  6. 6 Department of Ophthalmology, University of California, San Francisco, California, USA
  7. 7 Department of Epidemiology & Biostatistics
  8. 8 Institute for Global Health, University of California, San Francisco, USA
  1. Correspondence to Dr Jeremy Keenan, 513 Parnassus Avenue, Box 0412, University of California, San Francisco, San Francisco, CA 94143, USA; jeremy.keenan{at}

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Trachoma remains the world's leading infectious cause of blindness.1 Trachoma control programmes determine when to start and stop mass antibiotic treatments based on the prevalence of follicular trachoma (TF) in children aged 1–9 years, as assessed by examination of the upper tarsal conjunctiva using the WHO simplified grading system.2 According to the WHO classification, TF is defined as the presence of ≥5 follicles at least 0.5 mm in diameter. The original paper describing the WHO simplified grading system included a diagram of the everted conjunctiva with examples of follicles that were 0.5 mm in diameter.2 However, in our clinical experience, the follicles in this diagram seem to be less than 0.5 mm when considered relative to the size of the conjunctiva. In this article, we measured the size of the follicles on the WHO diagram relative to photographs of everted conjunctivae from clinical trials in Niger and Ethiopia in order to determine whether the follicles in the diagram meet the WHO threshold of 0.5 mm.


Trained photographers used Nikon D-series digital SLR cameras with Micro-Nikkor 105 mm f/2.8 …

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  • Contributors DM performed all measurements and wrote the first draft of the manuscript, AA, SG, ZT and PME organised field photography and organised the photographs; SNY, NES, BDG, TML and JDK administered training for the photographers and organised field activities in Niger and Ethiopia; SNY and JDK selected a random subset of photographs and TML and JDK performed statistical analyses. All authors edited the manuscript.

  • Funding The primary funders for this study were the Bill and Melinda Gates Foundation (grant number 48027) and the National Institutes of Health—National Eye Institute (grant number EY016214). The study also received support from the Bernard Osher Foundation, That Man May See, the Harper Inglis Trust, the Bodri Foundation, the South Asia Research Fund and Research to Prevent Blindness.

  • Competing interests None.

  • Ethics approval University of California, San Francisco Committee on Human Research, Emory University Institutional Review Board, Ethiopian Ministry of Science and Technology and the ethical committee of the Niger Ministry of Health.

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