Based on standard WHO definition, visual impairment reported as presenting visual acuity (PVA). The PVA was considered the uncorrected VA for subjects who do not have corrective eyeglasses. Presenting visual acuity impairment (PVAI) was classified as mild visual impairment, moderate visual impairment and severe visual impairment. Mild visual impairment, Moderate visual impairment and severe visual impairment were defined as presenting visual acuity between 6/12 to 6/18, 6/18 to 6/60, and 6/60 to 3/60 in the better eye.
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