The effect of fenofibrate therapy on laser treatment for diabetic retinopathy. O–E, observed–expected. Var, variance. For each trial, O−E is calculated from 2 × 2 contingency tables. OR is calculated by taking ln(OR) to be (O−E)/V with normal variance 1/V, where V = Var (O–E). Totals of (O−E) and of V yield inverse-variance–weighted averages of the ln(OR) values. For the FIELD trial, digitization software was used to extract numbers of events in the first year vs. later years.