Petri M, et al. - A total of 537 individuals with SLE in a large clinical cohort were repeatedly evaluated for hydroxychloroquine blood levels and tested for hydroxychloroquine retinopathy in order to address the frequency of hydroxychloroquine retinopathy and the role of hydroxychloroquine blood levels to recognize those at greater future risk of retinopathy. The overall prevalence of retinopathy was 4.3%. In the first 5 years, from 6 to 10 years, from 11 to 15 years, from 16 to 20 years and subsequent to 21 years of use, there was 1%, 1.8%, 3.3%, 11.5%, and 8.0% risk of retinopathy, respectively. Elderly people, higher BMI and longer term of hydroxychloroquine consumption were correlated with a higher risk of hydroxychloroquine toxicity. Moreover, higher hydroxychloroquine blood levels prognosticated later hydroxychloroquine retinopathy. Therefore, this data proves the use of hydroxychloroquine blood levels in prognosticating retinopathy, which, in turn, would allow clinicians to either reduce the dose or extend monitoring in those with high blood levels.