advertisement
Yip et al. (118) have documented an association with IOP and self-reported income and level of educational at-tainment in an analysis of a population-based study of older Chinese residents of Singapore Persons in the lowest income bracket had an IOP that was 1.3 mmHg higher than those in the highest income bracket. Adjusting for age and central corneal thickness reduced the magnitude of this effect to 0.97 mmHg, and further adjustment for systolic blood pressure and body mass index reduced this further to 0.72 mmHg, or about a 5% lower IOP in the left eye of the wealthiest persons. The findings were of a lesser magnitude and not statistically significant in the right eye. Similarly, those with the highest educational level had lower IOP which was of borderline significance in one eye in the adjusted models. While the authors state that 'socioeconomic status' (SES) is associated with IOP in the title and the conclusions, they have in fact found associations with self-reported monthly income (which does not fully capture family wealth) and with level of educational attainment. These are elements of SES, but the categorization of persons in this fashion is incomplete. The now famous Whitehall study of British civil servants showed an increase in mortality and illness when comparing those of a lower grade of employment to those of a higher one, even when employees differed by a single grade. SES is a complex phenomenon that likely affects health through varied mechanisms. The authors are to be commended on demon-strating a possible link with income and educational level and IOP. This finding raises the important question of what other unmeasured factors influence IOP, and what are the IOP regulatory mechanisms that are affected.