1. Veterans Affairs Boston Healthcare System, Surgical Service, Boston, Massachusetts, USA
2. Massachusetts Eye and Ear, Harvard Medical School, Department of Ophthalmology, Boston, Massachusetts, USA
3. Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, USA
4. Center for Preventive Ophthalmology and Biostatistics, University of Pennsylvania, Philadelphia, Pennsylvania, USA
5. Leonard Davis Institute, University of Pennsylvania, Philadelphia, Pennsylvania, USA
6. Center for Pharmacoepidemiology Research and Training, University of Pennsylvania, Philadelphia, Pennsylvania, USA