National RAAB; Sample size: 3164; Reference: Müller A1, Zerom M, Limburg H, Ghebrat Y, Meresie G, Fessahazion K, Beyene K, Mathenge W, Mebrahtu G. Results of a rapid assessment of avoidable blindness (RAAB) in Eritrea. Ophthalmic Epidemiol. 2011 Jun;18(3):103-8. doi: 10.3109/09286586.2010.545932.