The Value Of Scanning Laser Polarimeter With Variable Corneal Compensation (GDxVCC) In The Early Diagnosis Of Open-angle Glaucoma

Part One Correlation analysis between GDxVCCparameters and Visual Field indices in open-angle glaucomaPurpose: To evaluate the correlation between GDxVCC parametersand standard automated perimetry indices.Method: (1)Twenty-one normal subjects (42 eyes), 50 patientswith suspected open-angle glaucoma (SOAG,98 eyes), 31 patients withopen-angle glaucoma(OAG) were examined with GDxVCC, SAP(Standard automated perimetry) and SWAP(Short-WavelengthAutomated Perimeter).(2)The Comparison of average RNFL thickness(TSNIT), superior RNFL average thickness(SA), inferior RNFL averagethickness(IA), inter-eye symmetry(IES), standard deviation of RNFLthickness(TSD), nerve fiber indicator(NFI), mean defect(MD), patternstandard deviation(PSD) in three groups was analyzed. (3)Thecorrelation between GDxVCC indices and standard automated perimetryindices was analyzed with Pearson's correlation(r) and described withscatter plot.Results: (1) All the GDxVCC indices and visual field indicesshowed statistical differences significantly in normal control, SOAG andOAG groups (P＜0.01).(2) Between GDxVCC and SAP indices inOAG, IA (r=0.509), TSNIT (r=0.488), SA (r=0.482),TSD (r=0.347) were positive correlation with MD of SAP(P＜0.05); IA (r= -0.314), SA (r=-0.287), TSNIT(r=-0.268) were negative correlationwith PSD of SAP(P＜0.05); NFI was positive correlation with PSD(r=0.238) and was negative correlation with MD(r=-0.461, P＜0.05);Astatistically significant correlation was not found in healthy or suspectedsubjects.Conclusion: A statistically significant correlation was foundbetween most GDxVCC parameters and perimetry indices in patientswith glaucoma, but not in normal and suspected subjects.Part Two The sensitivity and specificity of GDxVCC in thediagnosis of open-angle glaucomaPurpose: To evaluate the sensitivity and specificity of GDxVCC inthe diagnosis of open-angle glaucoma and the joint application value ofGDxVCC, SWAP, SAP measurements.Method:(1) Twenty-one normal subjects(42 eyes), 31 patientswith open-angle glaucoma(OAG) were examined with GDxVCC,SApand SWAP.(2)The sensitivity and specificity of GDxVCC, SAP andSWAP on glaucoma diagnosis were calculated, Receiver's operatingcharacteristic (ROC) curves of RNFL parameters were described and compared.(3) The sensitivity and specificity of the joint or singlemeasurement of GDxVCC, SAP and SWAP were also analyzed.Results: (1) The area under ROC curve of GDxVCC parameterwere: NFI(0.87),IES(0.85),IA(0.80),TSNIT(0.77),SA(0.76)respectively.(2)The sensitivity of GDxVCC,SWAP, SAP were 80.6%,74.2%,67.8% respectively,the specificity were 95.4%,85.7%,76.2% respectively.(3)The sensitivity and specificity of Parallel test of GDxVCC, SAP were93.7% and 72.5% respectively; the sensitivity and specificity of Serialtest of them were 54.6% and 98.9% respectively. The sensitivity andspecificity of Parallel test of GDxVCC,SAP and SWAP were 98.38% and62.17% respectively; the sensitivity and specificity of Serial test of themwere 40.51% and 99.8% respectively.Conclusion: (1)NFI and IES are the best indices to distinguishnormal subjects from patients with glaucoma.(2) GDxVCC has the bestdiagnostic capability, SWAP is the second.(3) Parallel tests of GDxVCC,SWAP and SAP can increase sensitivity significantly to avoid misseddiagnosis and serial tests can increase specificity significantly to excludemisdiagnosis. Part Three The comparison of the sensitivity and specificityof GDxVCC, SWAP under different diagnostic criteriaPurpose: To evaluate the sensitivity and specificity of GDxVCC, SWAPand SAP under different definitions and joint application value.Methods: (1) Twenty-one normal subjects(42 eyes), 31 patients withopen-angle glaucoma(OAG) were examined with GDxVCC, SAP andSWAP.(2)The sensitivity and specificity of the joint or singlemeasurement of GDxVCC, SAP and SWAP under local diagnosticcriteria and overall diagnostic criteria were calculated.Results: (1)With the local diagnostic criteria, the sensitivity ofGDxVCC, SWAP and SAP were 95.9%, 93.5%, 90.3%, respectively,thespecificity were 70.7%, 66.7%, 71.4% respectively. With the overalldiagnostic criteria, the sensitivity of GDxVCC, SWAP and SAP were80.6%, 74.2%, 67.8% respectively,the specificity were 95.2%, 85.7%,76.2% respectively.(2)With the local diagnostic criteria, the sensitivityand specificity of Parallel test of GDxVCC, SAP were 99.6% and 50.5%respectively, the sensitivity and specificity of Serial test were 86.8% and91.6% respectively; The sensitivity and specificity of Parallel test ofGDxVCC, SWAP and SAP were 99.97% and 33.7% respectively, thesensitivity and specificity of Serial test were 81.0% and 97.2%respectively.Conclusion:(1) The local diagnostic criteria of GDxVCC, SWAP and SAP can increase sensitivity differently, but should pay more attention tocorrespondence and reproducibility to exclude misdiagnosis.(2) Though ithas limitation for the early-stage glaucoma, NFI is the comparativelyperfect discrimination indices for distinguishing normal subjects frompatients with glaucoma. (3)Under the local diagnostic criteria, the serialtest of GDxVCC, SAP, SWAP is the best clinical diagnostic strategywhich can improve the diagnostic level significantly.