Correlation Of The Occurrence Of Diabetic Retinopathy And Retinal Nerve Fiber Layer Thickness

Objective Diabetes mellitus (DM) can provoke the apoptosis of retinaganglion cells. The retinal nerve fiber layer (RNFL) is mainly composed of axons ofthe ganglion cells. The change in thickness of RNFL especially in the macular area ofdiabetes patient and the relationship with the occurrence and development of diabeticretinopathy (DR) is still unclear. The aim of the study was to investigate therelationship between the change of the thickness of RNFL around the optic disc andmacula, and the progress of diabetes and diabetic retinopathy in patients using afrequency domain optical coherence tomography (OCT). Comparisons were madebetween the patients suffering from diabetes without diabetic retinopathy and thepatients with diabetic retinopathy but no obvious pathological proliferative change.Age-matched patients without diabetes were enrolled as control.Method Thirty eyes of thirty Patients without diabetes (control),30eyes of26diabetic patients without retinopathy (NDR) and30eyes of30patients with mild ormoderate diabetic retinopathy but no obvious pathological proliferative change(NPDR) were involved in the study, according to international clinical classificationstandard for diabetic retinopathy. Two areas around the optic disc and maculaincluding the total average (G), their superior nasal (NS), superior temporal (TS),temporal (T), inferior temporal (TI), inferior nasal (NI) and nasal (N) sub-areas wereobserved. The total average and the respective thickness of RNFL in the sub-areaswere measured and compared between the groups of the patients.Results The values of thickness of RNFL around the optic disc for the NDR group were G（97.46±8.65）μm, NS（113.84±21.85）μm, TS（127.79±15.11）μm, T（71.06±10.84）μm, TI（137.88±22.13）μm, NI（110.85±22.64）μm and N（72.74±12.52）μm reSPectively. The values of thickness of RNFL around the opticdisc for the NPDR group were G（100.69±16.35）μm, NS（117.32±19.05）μm, TS（134.01±19.32）μm, T（79.83±12.02）μm, T（I149.56±24.30）μm, N（I115.75±27.56）μm and N（70.90.71±16.28）μm reSPectively. While the values of thickness of RNFLaround the optic disc for the control group were G （109.22±8.69） μm, NS（118.20±23.71）μm, TS（150.74±17.12）μm, T（79.93±6.93）μm, T（I158.77±18.27）μm, NI（127.79±24.34）μm and N（77.89±10.82）μm reSPectively. The totalaverage of the RNFL thicknesses and the RNFL thicknesses of the sub-areas of TS、T、TI、 NI in the patients of NDR group were significantly decreased (P <0.01),compared to that of the control group. While in the NPDR group, marked reductionsof RNFL thickness were observed in the total average of RNFL thickness and in thesub-areas of TS and N, when compared to the control (The total average of RNFLthicknesses and the RNFL thickness of the sub-areas of TS P <0.01, the sub-areas ofN P＜0.05).The RNFL thickness around the macula, for the NDR group, were G（33.47±3.39）μm, NS（39.27±5.30）μm, TS（31.35±3.56）μm, T（24.02±2.19）μm, T（I34.47±4.20）μm, N（I39.89±5.72）μm and N（36.31±4.75）μm reSPectively.The RNFL around the macula, for the NPDR group, were G（36.81±3.21）μm, NS（44.44±6.96）μm,TS（34.40±3.45）μm, T（25.71±3.10）μm, TI（37.47±4.43）μm, N（I43.74±5.54）μm and N（40.34±6.47）μm reSPectively. The RNFL around themacula for the control group were G（38.18±2.16）μm, NS（47.87±5.16）μm, TS（36.60±3.22）μm, T（28.27±2.37）μm, TI（39.28±4.14）μm, NI（44.64±4.28）μm and N（40.36±2.94）μm reSPectively. Compared with the control group, thethickness of RNFL in all areas of the NDR group was significantly decreased （P＜ 0.01）. In NPDR group significant decrease of the thickness of RNFL was detected inthe sub-areas of NS, TS and T (the sub-areas of T P＜0.01, the sub-areas of NS andTS P＜0.05), compared to the control.Conclusions The results of current study indicate that the decline of the RNFLthickness may occur before diabetic vasculopathy, which may be an earlypathological stage for the retina of the diabetic patients in the process of formation ofthe diabetic retinopathy. Frequency domain OCT can be used for quantitativeevaluation of the changes in the thickness of RNFL and the influence of retinalstructure by diabetes. OCT can be used as a diagnostic method of early diabeticretinopathy.