Teacher:In this task, you are given a passage which has a question and the context. You have to generate an answer to the question based on the information present in the context.
Teacher: Now, understand the problem? Solve this instance: Context: To determine the effect of suppression of vascular endothelial growth factor (VEGF) by monthly injection of ranibizumab on posterior retinal nonperfusion (RNP) in patients with diabetic macular edema (DME).', 'Unplanned retrospective analysis of prospectively collected data from 2 randomized, sham injection-controlled, double-masked, multicenter clinical trials.', 'Six hundred sixty-six patients with DME.', 'An independent reading center measured the area of RNP on fluorescein angiograms obtained in the phase 3 RISE and RIDE trials.', 'The percentage of patients with no posterior RNP.', 'The percentage of patients with no posterior RNP decreased in the sham group between baseline and month 24, but remained relatively stable in the 2 ranibizumab groups. After month 24, the sham group crossed over to receive monthly injections of ranibizumab 0.5 mg, and the differences between the sham and ranibizumab groups were reduced. The percentage of patients who showed an increase in posterior RNP from baseline increased over time in all 3 groups, but at a faster rate in the sham group, resulting in statistically significant differences at every time point between months 3 (9.6% vs. 18.5%; P = 0.016) and 24 (16.1% vs. 37.6%; P<0.0001) for ranibizumab 0.5 mg versus sham and from months 6 (12.3% vs. 23.0%; P = 0.013) through 24 (15.0% vs. 37.6%; P<0.0001) for ranibizumab 0.3 mg. Initiation of ranibizumab in the sham group at month 24 was followed by reduction in the percentage of patients with an increase in posterior RNP from baseline at months 30 and 36, whereas the 2 ranibizumab groups continued their gradual rise.\Question: Does neutralization of vascular endothelial growth factor slow progression of retinal nonperfusion in patients with diabetic macular edema?
Student:
Just as high VEGF levels contribute to progression of retinal nonperfusion in retinal vein occlusion, the same is true in patients with DME, suggesting that regardless of the underlying disease process, high levels of VEGF can cause closure of retinal vessels. However, our data also suggest that VEGF-induced worsening of retinal perfusion in DME is superimposed on another cause of more gradually worsening perfusion, possibly glucotoxicity. Thus, monthly injections of ranibizumab can slow, but not completely prevent, retinal capillary closure in patients with DME.