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Survey of blindness and visual impairment in Bioko, Equatorial Guinea
  1. C L Moser1,
  2. M Martín-Baranera2,
  3. F Vega3,
  4. V Draper4,
  5. J Gutiérrez4,
  6. J Mas5
  1. 1Ophthalmology Unit, Consorci Sanitari de la Creu Roja a Catalunya, Hospital de l'Hospitalet, L'Hospitalet de Llobregat (Barcelona), Spain
  2. 2Epidemiology Unit, Consorci Sanitari de la Creu Roja a Catalunya, Hospital de l'Hospitalet, L'Hospitalet de Llobregat (Barcelona), Spain
  3. 3Fundació Bosch i Gimpera, Barcelona, Spain
  4. 4Hospital Germans Trias i Pujol, Badalona, Spain
  5. 5Microbiology and Parasitology Department, Universitat de Barcelona, Agencia Española de Cooperación Internacional. Fundación Hospitalaria de la Orden de Malta, Spain
  1. Correspondence to: Dr Carlos L Moser, Av Josep Molins 29-41, E-08906 L'Hospitalet de Llobregat (Barcelona), Spain; cluis.moser{at}


Aims: This study was designed to estimate the prevalence of blindness and its main aetiologies in Bioko, an onchocerciasis endemic zone of Equatorial Guinea.

Methods: Random sampling was applied, proportionally to population distribution into urban or rural areas. All the subjects underwent a basic eye examination by trained nurses. In the presence of any ocular affection or a visual acuity of less than 0.3, the subject was visited by the ophthalmologist. This visit included direct and indirect ophthalmoscopy, anterior segment examination with a slit lamp, and intraocular pressure recording. Blindness and visual impairment were defined by using the WHO criteria.

Results: 3218 subjects were screened, with a mean age of 34.1 (SD 21.6) years, ranging from 1 month to 102 years (median 34 years). The overall prevalence of blindness was 3.2% (95% CI: 2.6% to 3.9%). Unilateral blindness was present in 4.2%. Visual impairment was diagnosed in 200 patients (6.8%). More than 20% of the acuities inferior to 0.7 improved when explored with a pinhole. The main causes of blindness were cataracts (61.3%); macular affection (25.3%), optic atrophy (16%), and glaucoma (13.3%). Ocular onchocerciasis was detected in 12 cases (0.4%).

Conclusion: Ocular onchocerciasis was very uncommon in an area of high endemicity. Results also pointed at the lack of basic ophthalmologist eye care and optician resources in the island.

  • blindness
  • Equatorial Guinea
  • onchocerciasis

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  • Series editors: W V good and S Ruit