The Early Diagnostic Value Of Ic-VEP Combined With GCIPL In Primary Open-angle Glaucoma

Background and ObjectivePrimary open angle glaucoma(POAG)is a chronic progressive optic neuropathy.Optic atrophy and visual field defect will appear in the process of development,and the chamber angle is always open when the intraocular pressure increases.However,unlike angle-closure glaucoma,although the intraocular pressure of POAG is a major risk factor,Some normal intraocular pressure glaucoma with optic nerve damage and visual field defect are normal and only appear as elevated intraocular pressure without optic nerve and visual field damage.The effect of intraocular pressure management in them is significantly reduced,and the difficulty of early diagnosis and treatment is increased.Most patients gradually lose vision during the secret course of POAG,and even only the central vision.and timely diagnosis and treatment are very important.Conventional diagnostic methods such as standard automatic perimeter(SAP)can detect glaucomatous visual field defects,but cannot sensitively detect damage to retinal ganglion cells(RGC)that occur before visual field defects.and it has strong subjectivity.Frequency-domain optical coherence tomography(SD-OCT)can judge the damage of the optic nerve by evaluating the thickness of the retinal nerve fiber layer(RNFL)and other parameters.However,RNFL has not changed significantly in the early stage of POAG RGC injury,and its application in early diagnosis is relatively limited.A variety of inspection methods for early diagnosis of POAG are constantly emerging and developing in practice on the basis of traditional inspection methods.Most of the examinations are based on the early RGC damage of POAG,in which SD-OCT can detect the ganglion cell complex(GCC).Cirrus HD-OCT is an instrument of SD-OCT.its ganglion cell analysis mode can accurately measure the thickness of RGC layer plus inner plexiform layer(GCIPL).And another new inspection method,isolated-check visual evoked potential(ic-VEP)is to separate the M cells in RGC for the purpose of early detection of glaucoma damage.In order to evaluate the value of ic-VEP combined with macular GCIPL in the early diagnosis of POAG,this study collects the relevant examination results of early,middle and advanced POAG patients and normal controls for comparative analysis.Materials and methods64 eyes of 64 patients with primary angle glaucoma are collected from November 2018 to October 2019 in the Second Affiliated Hospital of Zhengzhou University.According to the HAP classification standard,POAG patients are divided into 34 eyes in early POAG group and 30 eyes in middle and late POAG group,26 eyes of people with normal age and gender matched at the same time during the physical examination in our hospital served as the control group.All selected candidates were examined for visual acuity(including corrected vision),intraocular pressure,atrial angle,central corneal thickness,ic-VEP,perimetry,cirrus HD-OCT scanning disc and macular.The signal-to-noise ratio(SNR)of the ic-VEP and the GCIPL related parameters of the macular region are recorded.Statistical software is used to analyze the independent and combined diagnostic effectiveness of the SNR and GCIPL related parameters for early,middle and late POAG.Results(1)There are no significant differences in age,gender,diopter,and central corneal thickness between the early POAG group,the middle-late POAG group and the control group(P>0.05).There are significant differences in intraocular pressure(IOP),C/D and MD(P<0.01)between the early POAG group and the middle-late POAG group.The IOP and C/D of the early,middle and late POAG group are higher than those of the control group,and the MD are lower than those of the control group.The IOP and C/D of the middle-late POAG group are all greater than those of the early group,and MD was lower than that in the early group.(2)The SNR of the early,middle-late POAG groups is lower than that of the control group,and the differences are significant(P<0.01).The thickness of GCIPL in all areas,average thickness and minimum thickness are thinner than those in the control group,and the difference is significant(P<0.01).(3)GCIPL parameters,SNR and MD are positively correlated,and GCIPL parameters are more correlated;C/D and MD are negatively correlated.(4)The highest AUC value in the diagnosis of early POAG is the combined index of SNR and GCIPL(0.957),followed by SNR(0.904).The AUC of some GCIPL parameters is higher,such as the superior temporal region(0.853)and the minimum value(0.853),and the average value(0.826);the highest AUC value in the diagnosis of middle and late POAG is the GPICL nasal and inferior area(0.929),followed by the SNR(0.923).The AUC values of other GCIPL parameters are also higher,such as the average value(0.924),which are all around 0.9.In the diagnosis of early POAG,the highest diagnostic sensitivity is SNR(94.44%),and the highest specificity was the combined index of SNR and GCIPL(100.00%).In the diagnosis of middle and late POAG,the highest sensitivity is SNR(96.87%).Upper zone,lower zone and average(all 100%).In the diagnosis of early POAG,the largest Youden's Index is the combined index of SNR and the minimum value of GCIPL(0.9167),followed by the minimum value of GCIPL(0.7083)and SNR(0.6944).The largest Youden's Index in the diagnosis of middle and late stage POAG is the average GCIPL(0.9063),and all Youden's Index of GCIPL are greater than the SNR(0.764).Conclusions(1)ic-VEP is valuable for the diagnosis of early and middle-stage POAG,and GCIPL is more valuable for the diagnosis of POAG.(2)ic-VEP combined with GCIPL has a better ability to diagnose early POAG,and has higher sensitivity and specificity.