National RAAB; Sample size: 2862; Reference: Duerksen R1, Limburg H, Lansingh VC, Silva JC. Review of blindness and visual impairment in Paraguay: changes between 1999 and 2011. Ophthalmic Epidemiol. 2013 Oct;20(5):301-7. doi: 10.3109/09286586.2013.821497.