Error in Conversions. In the article titled"Retinal Microvascular Abnormalities in Patients Treated With External Radiation for Graves Ophthalmopathy, " published in the May issue of the ARCHIVES (2003;121:652-657), the conversions from rad to gray and centigray were incorrect. The correct conversions are as follows: 2500 rad (or 2500 cGy) = 25 Gy; 2000 rad (or 2000 cGy) = 20 Gy; 200 rad (or 200 cGy) = 2 Gy; 160 rad = 1.6 Gy; 40 rad = 0.4 Gy; 1 rad = 0.01 Gy. The ARCHIVES regrets the error.