| Diabetic retinopathy(DR) is one of the serious diabetic complications which can lead to blindness.As rapidly increasing of the incidence rate of diabetes mellitus in recent years,the prevention and treatment of diabetic retinopathy is becoming a tough challenge. Renin-angiotensin system is a typical endocrine system.Some researches show that there also is renin-angiotensin system in eye tissue which dose not belong to blood circulation system.Renin mRNA, angiotensin mRNA and angiotensin-converting enzyme mRNA can be expressed in human retina.When diabetic retinopathy occurs,the local renin-angiotensin system of eyes is activated, and participate in the progression of diabetic retinopathy.If angiotensin-converting enzyme inhibitors(ACEI) can play the same role of protection as in the case of patients with diabetic nephropathy not depending on the action of controlling blood pressure is becoming one of the focal points.The alleged evidence-based medicine is the clinical medicine followed evidence,which utilizes the best evidence at present to constitute the scheme of diagnosis and treatment on patients consciously,definitely and prudently. Evidence-based medicine which provides reliable and scientific evidendes for clinical research and health decision covered the medical fields of diagnosis, treatment,prevention and so on. Meta-analysis method is the core of evidence-based medicine.As a reliable, feasible,literature reviewed method, Meta-analysis can increase sample size, reduce bias and error, enhance the effectiveness of testing and finally produce reliable conclusions. As the researches going on, some controlled clinical researches about the effect of ACEI drugs on diabetic retinopathy in normotensive people with diabetes mellitus have been done.But the results are not adequate to provide an effectiveness test because of inconsistency of the results and small size of many samples.But until now there is still not relevant Meta-analysis or systematic review about these clinical studies, and it still lack of evidence-based medicine to support.In this study we are going to collect all relevantcontrolled randomized clinical trials, analyse and evaluate the effect of ACEI drugs on retinopathy in normotensive people with diabetes mellitus,so that we can increase sample sizes and testing efficiency, and then come to more reliable comprehensive conclusions.We hope to judge whether ACEI drugs can protect retina without depending on the action of controlling blood pressure,and at the same time provide a scientific evidence for the prevention and treatment of DR.Through computer,we searched the relevant literatures published in Cochrane Controlled Trials Registe, Ovid-medline Full Text Datebase,Embase Datebase,CBMdisc Datebase.At the same time we inspected the relevant ophthalmologic magazines,the proceedings of academic meeting and the references of related papers and reviews by hand.We also searched the Pubmed Datebase,Internet,Wanfang Datebase and China National Knowledge Infrastructure and so on and tried to find the literatures omitted.Finally,there are 862 papers are obtained.According to the including and excluding standards,there are 7 randomized controlled trails involved in this study. On the basis of Jadad scale,five papers are 3 points(high-quailty study) and the other two ones are 1-2 points(low-quailty study).In this study,the Meta-analysis software package RevManManage4.2 Which the Cochrane Collaboration provide to compute statistically is used to complete the statistical analysis. The targets type of this study is two sort variable,so OR is selected as pooled variable.According to the result of heterogeneity test ,7 recearches which have homogeneity are carried on by fixed effects model (Peto method) combining variables and the test of combining impact variables are made through forest plot.Because there are 5 involved studies mentioned the cases lost and withdrawed from them,I do the per protocol analysis(PP analysis) and intention to treat analysis (ITT analysis) and compare the two results to determine the reliability of the conclusion.By excluding the study which dose not use blind method and exchanging fixed effects model and random effects model and amount of effect varied(OR and RR),the sensitiveness analysis are made.Then we analyse the publication bias through estimating funnel plot.The result shows that in PP analysis OR(fixed)95%CI 0.38[0.29 , 0.51]<1,overall effectZ=6.59(P<0.00001);in ITT analysis OR(fixed)95%CI 0.45[0.35 ,0.58]<1,overall effect Z=6.20(P<0.00001).There is little distinction between the results of PP analysis and ITT analysis.So it can be explaind that the cases lost and withdrawed from the five studies included do not chage the fanal conclusion of this Meta-analysis.In sensitiveness analysis,we get OR(fixed)95%CI0.37[0.27,0.49] through excluding the study which dose not use blind method.By exchanging fixed effects model and random effects model and amount of effect varied (OR and RR),wen get RR(fixed)95%CI0.50[0.41,0.62],RR(random)95%CI0.51[0.41,0.63], OR(fixed)95%CI0.38[0.29,0.51],OR(random)95%CI0.38[0.29,0.51],which shows slight diversities of all the results.It proves that the analysis result is relatively steady. The funnel plot of this sdudy show a little asymmetric,which demonstrate that there is potential publication bias of the included literatures .From above results, we can draw such conclusion : ACEI drugs can effectively control occurrence and progression of diabetic retinopathy in the normotensive people with diabetes mellitus,and the effect dose not depend on its own role in lowering blood pressure. However, because of the small size in some samples,low quality of the individual trails,potential publication bias, limitation of the number of randomized controlled trials especially in China,and the existence of individual confounding factors in this study, completely accurate conclusions can not been drawn.So we still need to launch a series of large-scale, multi-center, prospective, double-blind, randomized controlled clinical trials so as to expand the sample size and then to provide sufficient evidence for ACEI drugs in ophthalmology for clinical practice. |
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