The Relevance Study Between Diabetic Corneal Neuropathy And Diabetic Retinopathy

Background and objective:Diabetes is one of the global public health problems.Diabetic retinopathy(DR)and Diabetic corneal neuropathy(DCN)respectively are common microvascular complications and neurological complications for the eyes.It is difficult to determine the severity of the retinal microvascular lesions of DR when the refractive stroma is not clear.In vivo confocal microscopy(IVCM)is the only way to observe the corneal nerve fibers inspection method in clinical.Due to the limited check method.This lead to DCN easily neglected.Diabetes has a very close relationship between neurological complications and microvascular complications.But,it is not clear how has the relationship between DCN and DR.If the disease severity is closely related to both,DCN can predict disease severity of DR.In addition,early intervention to prevent blood glucose,blood pressure,blood lipid have an important role for preventing the development of DR.IVCM has a microscopic view for corneal nerve fibers.If nerve damage,such as DCN,can early detection before microvascular lesions,it is to prompt us to intervene DR as soon as possible.Therefore,this study has two objectives.On one hand,this study want to confirmed IVCM have clinical application value of DCN,and explored the clinical disease severity relevance between DCN and DR.On the other hand,this study want to observe the changes of corneal nerve fibers(CNF)and retinal nerve fiber layer(RNFL)in diabetic patients without diabetic retinopathy,and the relevance between CNF and RNFL.To provide early screening indicators for intervention of DR.Subjects and methods:Part 1: One hundred and twenty eyes of 120 patients with Type 2 diabetes mellitusand 30 eyes of 30 healthy participants were scanned with in vivo corneal confocal microscopy.Diabetic patients were classified into four groups: patients without diabetic retinopathy(NDR),patients with mild or moderate non-proliferative diabetic retinopathy(mNPDR),patients with severe non-proliferative diabetic retinopathy(sNPDR)and patients with proliferative diabetic retinopathy(PDR).Images of sub-basal nerve plexus were quantified including nerve fiber length(NFL),nerve fiber density(NFD),nerve fiber branch density(NFB),and nerve tortuosity(NT).Part 2:Forty eyes of 40 patients with Type 2 diabetes mellitus,who were found no diabetic retinopathy,were examined by optical coherence tomography(OCT)and in vivoconfocal microscope(IVCM).Forty eyes of 40 healthy participants were only scanned using OCT served as RNFL contol group,and another forty eyes of 40 healthy participants were only scanned using IVCM served as CNF contol group.The thickness of superior,inferior,nasal,temporal and average RNFL to optic disc were measured using OCT.Corneal nerve fibers length and Corneal nerve fibers density were measured using IVCM.Results:Part 1:NFL,NFD and NFB were found to be significantly lower in diabetic patients than those of controls(P<0.01),NT was significantly greater in diabetic patients when compared to controls(P<0.01),while the difference was not statistically significantbetween sNPDR and PDR patients(P>0.05).NFL?NFD?NFB were negatively correlated with the severity of DR(r=-0.875?-0.866?-0.798,P=0.000?0.000?0.000),NT were positively correlated with the severity of DR(r=0.693,P=0.000).Part 2:The diabetic patients showed decreased thickness of inferior RNFL when compared to controls(P=0.003).No significant differences were found in the thickness of superior,nasal,temporal and average RNFL(P>0.05).The diabetic patients were also found to have lower NFL and NFD(P<0.01).What's more,in diabetes patients,the average RNFL were positively correlated with NFL and NFD(r = 0.518,P<0.01;r = 0.484,P = 0.002),and the inferior RNFL were also positively correlated with NFL and NFD(r = 0.607,P<0.01;r = 0.573,P<0.01).Conclusions:1.IVCM is a sensitive and effective method in evaluating DCN.Diabetic patients had different severity of corneal nerve fiber loss and corneal nerve tortuosity increased.2.There was close correlation of disease severity between DCN and DR.The progress of corneal neuropathy was correlated with the severity of DR.DCN can serve as evaluation indicators for the severity of DR.3.CNF and RNFL were early damaged in diabetic patients without retinal microvascular lesions.RNFL decreased in the inferior quadrant of retina.The loss of CNF was significantly correlated with the decrease of RNFL.CNF and RNFL can serve as early screening indicators for intervention of DR.