LAUSR

Objectives Two epidemiologic studies have found evidence of increasing risk of retinal detachment (RD) with increasing occupational lifting and related physical efforts. Beyond case reports, there is little evidence to explain this association. We hypothesise two alternative mechanisms and explore their implications for epidemiology. Methods Through literature review and discussions with retinologists, we developed hypotheses that predict different etiologic time windows for an effect of lifting on RD. The role of myopia in RD is better-understood, and provides important clues about possible roles of physical activity. Inter-ocular pressure (IOP) is likely to play a mediating role, and there are experimental studies of the effects of physical activity on IOP that may also provide useful evidence for understanding RD. Results and Conclusions Hypothesis 1: brief increases in IOP caused by lifting increase the risk of retinal tears during posterior vitreous detachment (PVD) - a normal ageing process. This suggests that there may be an elevated risk of retinal tear in the weeks following PVD. If this is correct, lifting during other times may not increase risk. Hypothesis 2: A long, slow pattern of increases in IOP from regular heavy lifting accelerates vitreous liquefaction, so that retinal tears are more likely to occur. Under this hypothesis, changes in IOP don’t cause tears directly, but instead a long-term pattern of ”peaks” in IOP may increase the chances of an RD. If this is correct, risk of RD would be associated with a longer history of heavy lifting.