Change Of Choroidal Thickness In Diabetic Retinopathy By Using Enhanced Depth Imaging Optical Coherence Tomography

Research backgroundAs the prevalence of diabetes mellitus increased around the world,diabetic retinopathy,which is one of the main complication of diabetes,is getting more and more attention,and has become the key aspect of prevention and treatment of blindness in 21st century.Diabetic retinopathy is actually microvascular lesion caused by diabetes.Choroid is a layer consisting of vascularized tissue and its blood flow accounts for 90%of the whole intraocular blood,of which about 70%concentrated in the choroidal capillary layer.Choroid plays an important role in the blood-supply for the retinal outer layer(including retinal pigment epithelial cells and photoreceptor cells).At the same time,choroidal capillaries are an important component of the blood retinal barrier,its lesion can directly affect the function of the extra blood retinal barrier,and ultimately may accelerate the occurrence of diabetic retinopathy and diabetic macular edema.However,the current international problems on the incidence of diabetic choroidopathy and diabetic retinopathy as well as the relationship between them has not yet been concluded.Choroidal thickness can indirectly reflect the blood perfusion and tissue metabolic status of choroid.With the development and improvement of inspection techniques,the measurement of choroid thickness in live eye has become possible.Using the enhanced depth imaging optical coherence tomography can clearly show the whole layer of choroid and its thickness quantitative measurement.The results of the studies on change of choroid thickness in diabetic retinopathy is still a big controversy.Therefore,our study intends to use EDI-OCT measurement to figure out the change of subfoveal choroidal thickness in diabetic retinopathy,to analyze the relationship between choroidal thickness and diabetic retinopathy,and to provide a basis for further study of the relationship between diabetic choroidopathy and diabetic retinopathy.Part 1 Change of choroidal thickness in different stages of diabetic retinopathy by using enhanced depth imaging optical coherence tomographyObjective:To study the relationship between the choroidal thickness and diabetic retinopathy(DR)by using optical coherence tomography(OCT)to measure and compare the subfoveal choroidal thickness(SFCT)of patients who are in different stages of DR.Method:137 patients(250 eyes)with diabetes were included in this project and were divided into three groups according to the international clinical classification standard of diabetic retinopathy:non-diabetic retinopathy(NDR),non-proliferative diabetic retinopathy(NPDR)and proliferative diabetic retinopathy(PDR).In addition,23 cases(42 eyes)of normal volunteers constituted the Normal group.All the objects accepted an optical coherence tomography enhance depth imaging(EDI)examination and the SFCT was measured and analyzed.Result:The average SFCT of Normal,NDR,NPDR and PDR groups would like to be(332.54±13.77)?m,(270.84±20.84)?m,(313.26±47.82)?m and(321.27±83.36)?m.Significant difference was found between these four groups(P=0.03).Among them SFCT of NDR group was lowest and was significantly thinner than that of Normal group(P<0.05)and that of NPDR group(P<0.05),while no significant difference was found between NDR and PDR groups,and either did between Normal group,NPDR and PDR groups.Conclusion:The SFCT of diabetics are probably becoming thinner before they have diabetic retinopathy.SFCT of NPDR was much thicker than that of NDR while the difference between NPDR,PDR and Normal group is not significant.Part 2 Change of choroidal thickness and photoreceptor layer continuity in diabetic macular edema by using enhanced depth imaging optical coherence tomographyObjective:To observe the change of subfoveal choroidal thickness(SFCT)and the integrity of external limiting membrane(ELM)as well as ellipsoidal zone(EZ)of diabetic macular edema(DME)by using enhanced depth imaging optical coherence tomography.Method:100 patients(162 eyes)with diabetic retinopathy were included in this project and were divided into two groups according to the present of diabetic macular edema by fundus fluorescein angiography:non-DME group and DME group.In addition,23 cases(42 eyes)of normal volunteers constituted the Normal group.All the objects accepted an OCT examination and indexes above were measured and analyzed.Result:Mean SFCT between Normal(332.54±13.77pm),non-DME(309.68±17.54?m)and DME(319.59±33.00?m)groups had no statistical significance(P=0.67).Correlation analysis showed that there was a negative correlation between SFCT and CRT in patients with DME(r=-0.537,P<0.05),while there was no correlation between SFCT and CRT in Normal and non-DME patients(P = 0.12,P = 0.09).There were 7 eyes with disrupted ELM in the non-DME group and 31 eyes in the DME group.Difference between them had been proved to be significant(P<0.05).Similarly,the integrity of EZ had significant difference between non-DME group(with 12 eyes disrupted)and DME group(with 37 eyes disrupted)(P<0.05).Conclusion:There is no difference of SFCT between DME,non-DME and normal people.The SFCT of patients with diabetic macular edema is gradually thinning with the increase of CRT.Compared with non-DME,patients with DME have higher incidencein of ELM and EZ damage.