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July 18, 2012

Retinal Detachment and Fluoroquinolones—Reply

Author Affiliations

Letters Section Editor: Jody W. Zylke, MD, Senior Editor.

Author Affiliations: Therapeutic Evaluation Unit, Child and Family Research Institute of British Columbia, Vancouver, Canada (Dr Etminan; metminan@popi.ubc.ca); Department of Epidemiology, Biostatistics and Medicine, McGill University, Montreal, Canada (Dr Brophy); and Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, Canada (Dr Maberley).

JAMA. 2012;308(3):233. doi:10.1001/jama.2012.6634

In Reply: Dr Nowroozzadeh requests information on the study power. For past use, the relatively narrow confidence interval (RR, 1.03; 95% CI, 0.89-1.19) indicates sufficient power; however, the wider confidence interval with recent use (RR, 0.92; 95% CI, 0.45-1.87) reveals less power to reliably estimate an association with retinal detachment. This is not surprising given the short exposure window for recent use (7 days) compared with that for past use (8 to 365 days prior to index date). Nowroozzadeh also suggests examining the effect of cumulative dose. The small number of exposed cases did not allow us to adequately examine the effect of dose. We agree that future studies should examine this question.