In the trial, 4mg and 1mg doses will be evaluated. The former will be used because it is the dose that is currently most commonly used in clinical practice and the latter because there is reasonable evidence for efficacy and the potential for lower risk. Although there is good reason to believe that a 1mg dose will reduce the macular edema, it is possible that the retreatment rate will be higher with this dose compared with 4mg since the latter will remain active in the eye for a longer duration than the former. Insufficient data are available to warrant evaluating a dose higher than 4mg at this time.