Table 1
Definitions and assumptions associated with blindness, low vision, vision impairment, unmet and met refractive error and presbyopic need, and refractive error and presbyopia coverage rates
| MPN, met presbyopic need; MREN, met refractive error need; PCC, presbyopic correction coverage; RECC, refractive error correction coverage; UPN, unmet presbyopic need; UREN, unmet refractive error need. | |
| Vision | |
| Blindness | Presenting distance vision worse than 6/60 in the better eye |
| Low vision | Presenting distance vision worse than 6/18, but at least 6/60, in the better eye |
| Vision impairment | Presenting distance vision worse than 6/18 in the better eye (being the combination of low vision and blindness) |
| Refractive error | |
| Refractive error requiring correction | Assumptions |
| Individuals with distance vision worse than 6/18 in the better eye, who do improve to at least 6/18 with pinhole, will benefit from refractive error correction | • Individuals with uncorrected vision of 6/18 or better in the better eye, do not have vision-impairing refractive error and do not require refractive error correction |
| • Individuals with uncorrected vision of worse than 6/18 in the better eye, with vision that does not improve to at least 6/18 with pinhole, will not benefit from refractive error correction | |
| • Individuals with uncorrected vision of worse than 6/18 in the better eye, with vision that does improve to at least 6/18 with pinhole, will require refractive error correction | |
| • Individuals with corrected vision of worse than 6/18 in the better eye, improving to at least 6/18 with pinhole, have undercorrected refractive error and will require replacement spectacles | |
| • Individuals wearing distance spectacles that provide vision of 6/18 or better in the better eye have a visually significant refractive error and require those spectacles to achieve this vision | |
| UREN | |
| A measure of the combined uncorrected and undercorrected refractive error in a defined population | UREN = number with refractive error and presenting vision, with correction if used, of worse than 6/18 in the better eye |
 | |
| MREN | |
| A measure of the penetration of correction of refractive error to 6/18 or better in a defined population | MREN = number with vision-impairing refractive error who wear distance spectacles and have presenting corrected vision of 6/18 or better in the better eye |
 | |
| RECC | |
| A measure of vision-impairing refractive error that is corrected to 6/18 or better |  |
| Presbyopia | |
| Presbyopia requiring correction: | Assumptions: |
| Individuals aged ⩾40 years with binocular near vision of worse than N8, who have at least 6/18 distance vision with pinhole, will benefit from presbyopic correction | • Individuals <40 years who cannot see N8 unaided binocularly may have a refractive error but not presbyopia |
| • Individuals aged ⩾40 years who do not see N8 binocularly and have distance vision worse than 6/18 in the better eye with pinhole will not benefit from presbyopic correction | |
| • Individuals aged ⩾40 years who see N8 unaided binocularly do not require presbyopic correction | |
| • Individuals aged ⩾40 years with no near correction and who cannot see N8 binocularly have presbyopia requiring correction | |
| • Individuals aged ⩾40 years wearing near correction who cannot see N8 binocularly have presbyopia requiring correction | |
| • Individuals aged ⩾40 years and wearing near correction that provide vision of N8 or better binocularly have vision-impairing presbyopia and require spectacles to achieve this vision | |
| UPN | |
| A measure of the combined uncorrected and undercorrected presbyopia in a defined population | UPN = number aged ⩾40 years and presenting near vision, with correction if used, of worse than N8 binocularly |
 | |
| MPN | |
| A measure of the penetration of correction of presbyopia to N8 or better binocularly in a defined population | MPN = number aged ⩾40 years with vision impairing presbyopia who wear near spectacles and have presenting corrected vision of N8 or better binocularly |
 | |
| PCC | |
| A measure of presbyopia requiring correction that is corrected to N8 or better binocularly in those aged ⩾40 years |  |