In Reply We agree that market forces and contractual arrangements can contribute to some of the geographic variation noted in our study. All of the data to which we had access for our study came from patients who were receiving their care from the same managed-care network. We did not have access to data capturing the care of patients with other forms of health insurance. Because the US health care system has many different public and private health care insurers and there is not yet a single data source that captures care of patients across insurance plans (although the American Academy of Ophthalmology Intelligent Research in Sight [IRIS] Registry may address this in the future), it is challenging for researchers to fully capture the extent by which market forces are driving the geographic variation in care noted. For now, we welcome other researchers to replicate our study using other data sources to help answer this important question.