DEC 11, 2012
Three-year study results from the Diabetic Retinopathy Clinical Research Network show that focal/grid laser treatment at the introduction of intravitreal ranibizumab is no better, and possibly worse, for vision outcomes than deferring laser treatment for at least 24 weeks in diabetic macular edema (DME) involving the fovea and with vision impairment.
Investigators reviewed the three-year outcomes of 361 patients with diabetic macular edema (DME) who received 0.5 mg ranibizumab combined with prompt or deferred (≥24 weeks) focal/grid laser treatment as part of a previously conducted randomized trial.
At three years, the mean improvement in visual acuity change was 2.9 letters greater with deferred laser treatment compared with prompt laser treatment. More patients in the deferred laser group had a ≥10 letter gain (56 percent vs. 42 percent), and fewer had a ≥10 letter loss (5 percent vs. 10 percent). The authors noted that some of the differences in visual acuity may be due to the fewer ranibizumab injections in the prompt laser group (12) than the deferred group (15).
They write that the continued beneficial effect on visual acuity seen in the first six months through at least three years of follow-up despite a steadily decreasing number of injections of ranibizumab suggests that this treatment protocol is not just transiently blocking the effects of VEGF on macular edema. Rather, it may be having a more fundamental effect on the basic mechanism(s) of the disease. Another possibility is that DME resulting from VEGF has a limited life span of activity and can resolve after one to two years in many cases.
They conclude that further studies are necessary to evaluate whether this is a drug-specific drug effect on the disease or a difference in the natural history of retinal vascular diseases.