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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. 1Francis I. Proctor Foundation, University of California, San Francisco, USA
  2. 2Faculté des Sciences de la Santé, Université Abdou Moumouni de Niamey, Niamey, Niger
  3. 3Programme National de Santé Oculaire, Niamey, Niger
  4. 4The Carter Center Ethiopia, Addis Ababa, Ethiopia
  5. 5The Carter Center, Atlanta, USA
  6. 6Department of Ophthalmology, University of California, San Francisco, California, USA
  7. 7Department of Epidemiology & Biostatistics
  8. 8Institute 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}ucsf.edu

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Introduction

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.

Methods

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

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