Insulin-like Growth Factors and Diabetic Retinopathy

To the Editor: The cautious hypothesis of Merimee et al. (Sept. 1 issue) that high levels of insulin-like growth factor (IGF) I contribute to or cause accelerated proliferation of new vessels is not warranted on the basis of their data.¹ First of all, this was a cross-sectional analysis; patients were not studied prospectively to determine whether IGF levels could predict which patients were at high risk of proliferation. An association, if indeed there was one, is therefore weakened. Secondly, one would like to be given information on factors known to be associated with retinopathy, such as the duration of disease.