National RAAB; Sample size: 3397; Reference: Rius A, Guisasola L, Sabidó M, Leasher JL, Moriña D, Villalobos A, et al. Prevalence of visual impairment in El Salvador: inequalities in educational level and occupational status. Rev Panam Salud Publica. 2014;36(5):290–9. and Silva, J. National surveys of avoidable blindness and visual impairment in Argentina, El Salvador, Honduras, Panama, Peru, and Uruguay. Rev Panam Salud Publica 2014;36(4):214–8.