Socioeconomic position and eye health outcomes: identifying inequality in rapid population-based surveys

OBJECTIVE: Monitoring health outcomes disaggregated by socioeconomic position (SEP) is crucial to ensure no one is left behind in efforts to achieve universal health coverage. In eye health planning, rapid population surveys are most commonly implemented; these need an SEP measure that is feasible to collect within the constraints of a streamlined examination protocol. We aimed to assess whether each of four SEP measures identified inequality-an underserved group or socioeconomic gradient-in key eye health outcomes. DESIGN: Population-based cross-sectional survey. PARTICIPANTS: A subset of 4020 adults 50 years and older from a nationally representative sample of 9188 adults aged 35 years and older in The Gambia. OUTCOME MEASURES: Blindness (presenting visual acuity (PVA) <3/60), any vision impairment (VI) (PVA <6/12), cataract surgical coverage (CSC) and effective cataract surgical coverage (eCSC) at two operable cataract thresholds (<6/12 and <6/60) analysed by one objective asset-based measure (EquityTool) and three subjective measures of relative SEP (a self-reported economic ladder question and self-reported household food adequacy and income sufficiency). RESULTS: Subjective household food adequacy and income sufficiency demonstrated a socioeconomic gradient (queuing pattern) in point estimates of any VI and CSC and eCSC at both operable cataract thresholds. Any VI, CSC <6/60 and eCSC <6/60 were worse among people who reported inadequate household food compared with those with just adequate food. Any VI and CSC <6/60 were worse among people who reported not enough household income compared with those with just enough income. Neither the subjective economic ladder question nor the objective asset-wealth measure demonstrated any socioeconomic gradient or pattern of inequality in any of the eye health outcomes. CONCLUSION: We recommend pilot-testing self-reported food adequacy and income sufficiency as SEP variables in vision and eye health surveys in other locations, including assessing the acceptability, reliability and repeatability of each question.