Operational Definitions

The World health organization (WHO) definitions’ of visual impairment was used to defined blindness; Blindness was defined as presenting visual acuity of less than 3/60 in the better eye.¹² The International Society of Geographical and Epidemiological Ophthalmology classification was used to diagnose glaucoma.¹³ Age-related macular degeneration (AMD) was diagnosed based on the International ARMD Epidemiological Study Group.¹⁴ Whether the presence or absence of Diabetic retinopathy in diabetic patients was assessed based on the Early Treatment Diabetic Retinopathy Study definition.¹⁵ Refractive error was considered when the spherical equivalent (SE) was ≥±0.50DS following full refraction. Hypertension and/or diabetes were assigned to the participants based on referring their medical folder and from their response whether confirmed diagnosis of these conditions and their respective medications are present.

Education status was categorized as non-formal education (illiterate, able to write and read with no formal schooling) and formal education (from primary school to university).