To the Editor In their article on geographic variation in the rate and timing of cataract surgery in US communities, Kauh et al1 analyzed beneficiary records from a nationwide managed-care network provided by OptumInsight, a subsidiary of UnitedHealth Corp. The authors found considerable variation in age at first cataract surgery and the median time between diagnosis and actual surgery. Analysis was conducted with regression modeling that included a host of patient, environmental, and socioeconomic variables. What may influence the rate of discretionary surgery more than any of the factors in their model, however, is local competition among managed-care organizations. As a remedy to control the rising cost of health care, managed care has developed a number of strategies that effectively alter medical utilization.2 Market forces dictate what tools managed-care organizations select to regulate consumption. It would seem crucial in any study assessing variation of cataract surgery among managed-care groups to adjust for the effects that factors such as balancing billing or capitation arrangements (to name just a few) have on surgery. Although these contractual agreements are likely important determinants of use, we realize the improbability of accessing this proprietary information. Seasoned health policy researchers have tried and then lamented that “rationing within managed care is a complex, heterogeneous, and poorly understood business. It involves hundreds of decision points within managed care organizations, making direct regulation of these practices costly, complex, and difficult to monitor.”3 On the other hand, it seems that unless we acknowledge the influence that competition among managed-care organizations has on discretionary surgery, a true understanding of geographic variation of cataract surgery will remain elusive.