EDITOR-Reidy et al found that 6% (92 of 1547) of an elderly population had serious and potentially remediable visual impairment (<6/60) and far higher numbers had less serious impairment.1 Since many of these people were not in touch with eye services it would be easy to conclude that, for example, the volume of cataract surgery should be substantially increased. The findings are important but caution is needed in drawing conclusions for service provision. Case definitions are critical in epidemiological investigations. The …