An evaluation of a community-based vision care programme for the elderly

Background

This study evaluated the real-world effectiveness and potential cost-effectiveness of a community-based vision care programme for the elderly population aged 60 years or above.

Methods

Data from a total of 8899 subjects participating in a community-based comprehensive vision care programme from 2015 to 2019 were analysed to evaluate the effectiveness of the programme in terms of the prevalence of distance visual impairment (VI), the change in the prevalence of distance VI after refractive error correction, and the types of ocular disorders suspected. Distance VI was defined as a) visual acuity (VA) worse than 6/18 in any eye (worse eye) and b) VA worse than 6/18 in the better eye. The cost-effectiveness from the funder’s perspective was also estimated in terms of cost per distance VI avoided.

Results

Based on the presenting vision of the worse eye, the prevalence of distance VI was 39.1% (3482/8899, 95% CI: 38.1%-40.1%) and reduced to 13.8% (1227/8899, 95% CI: 13.1%-14.5%) based on best-corrected VA. Referenced to the presenting vision of the better eye, the prevalence of distance VI was 17.3% (1539/8899, 95% CI: 16.5%-18.1%) and decreased to 4.2% (373/8899, 95% CI: 3.8%-4.6%) with best optical correction. Uncorrected refractive error was the major cause of presenting distance VI. From the funder’s perspective, the cost per distance VI case prevented was HK$1921 based on VA in the worse eye and HK$3715 based on the better eye.

Conclusion

This community-based programme identified distance VI in the best eye of 17 out of every 100 subjects. With appropriate new or updated distance optical corrections, distance VI was reduced to about 4 in 100 subjects. Visual impairment in the elderly is common even in a relatively affluent city. A model of care which could minimise avoidable distance VI would bring benefits at individual and societal levels.

The nature of the oil phase and the release of solutes from multiple (w/o/w) emulsions

The effect of the nature of the oil phase of w/o/w emulsions stabilized by interfacial complexation between span 80 (sorbitan mono-oleate) and albumin has been studied. The long-term stability of the systems has been assessed by photomicrography and by measuring the quantity of an internal marker (NaCl) remaining entrapped with time. The number of multiple oil drops and the diameters of the internal aqueous droplets were determined over 6 weeks, and the amounts of NaCl entrapped over the same period were followed. There were no significant changes in w/o/w emulsions prepared with a range of hydrocarbons (octane, dodecane, hexadecane, toluene and cyclohexane), indicating stable multiple emulsions. The release of NaCl and 5-fluorouracil (5-FU) separately entrapped in the internal aqueous phase of w/o/w emulsions was measured. Diffusion of the un-ionized species of 5-FU across the oil phase or through localized thin oil lamellae is the primary transport mechanism. In the presence of surface active agents, water is solubilized in inverse micelles which would possess the ability to solubilize other water-soluble components, such as NaCl and 5-FU. The mixed inverse micellar units of Span 80 and polysorbate (Tween) 80 therefore act as solute carriers across the liquid hydrocarbon membrane separating the two aqueous phases of the emulsions. The main factor in determining the differences in rates of release from the hydrocarbon emulsions appears to be the droplet size of the internal aqueous phase.