A Comparison Study On Structural And Functional Changes In Macular Region Of The Glaucoma

Part One:Local Retinal Ganglion Cell Thickness Can Be Measured in Patients with Glaucoma Using Frequency-Domain Optical Coherence TomographyObjective:To explore the feasibility of obtaining a local measure of the thickness of the retinal ganglion cell layer in patients with glaucoma using frequency-domain optical coherence tomography(FD-OCT) and a computer assisted manual segmentation procedure.Methods:FD-OCT scans of 3D and horizontal line were obtained from one eye of 26 glaucoma patients and 20 control subjects.The thickness of various layers was measured with a manual segmentation procedure aided by a computer program.The patients were divided into low and high sensitivity groups based upon their foveal sensitivity on standard automated perimetry.Results:The thicknesses of the RGC plus inner plexiform and the retinal nerve fiber layers of the low sensitivity group were significantly thinner than those of the high sensitivity group.While the thickness of these layers in the patients was thinner than controls,the thicknesses of INL and receptor layer were similar in all 3 groups. Further,the thinning of the RGC+layer in one glaucoma eye showed qualitative correspondence to the loss in 10-2 visual field sensitivity.Conclusions:Local measures of RGC layer thickness can be obtained from FD-OCT scans using a manual segmentation procedure and these measures show a qualitative agreement with visual field sensitivity. Part Two:Reliability Study of Manual Segmentation for Retinal Layers Using Computer Assisted ProcedureObjective:To explore a training procedure to the trainee on segmenting the retinal layers using computer assisted program and discuss the reliability of segmentation for providing information to the automatic algorithm.Methods:Forty FD-OCT line scans from 40 individuals were divided into 2 sets of 20,the Training Set and Test Set.Each set had scans from 10 individual with normal vision and 10 patients with glaucoma.The segmentation was divided into 2 sessions, Training Session and Testing Session.Trainees and experts segmented 20 scans in the Training Session with teaching and consulting.In the Testing Session,trainees and experts completed segmentation for another 20 scans without consulting.The thickness of the RNFL,RGC+ and total retina were calculated based on the boundaries of each layer.Concordance correlation coefficient of the thickness of each layer and the average thickness of each layer were calculated between trainees and experts.Results:For the total retinal thickness,the concordance correlations were very good for both trainees and for all 20 scans with a median of 0.999(mean:0.998) and 0.999 (mean:0.998) for trainee 1 and 2,respectively.The average total retinal thickness also showed good agreement.The concordance correlation of the RNFL was slight lower than the total retina.Compared to the trainee 2 with a median of 0.972(mean:0.892), trainee 1 was worse with a median of 0.940(mean:0.851).The average thickness of RNFL showed good agreement.The agreement was slightly better for trainee 2, whose median difference was-0.3μm,as compared to a median difference of 3.4μm for trainee 1.Trainee 1's RNFL thickness was constantly thicker than trainee 2 and experts.For the correlation of the RGC+ thickness,trainee 1 had a median of 0.934 (0.932) and trainee 2 had a median of 0.980(mean:0.967).The median difference of trainee 1 was 3.5μm and trainee 2 had a median difference of 0μm.The average thickness of RGC+ also showed good agreement.Conclusions:Trainees showed good agreement to the thickness of total retina,RNFL and RGC+ after training session.Training should contain a test session and quantitative analysis.Computer assisted manual segmentation can be used to assess segmentation done by algorithms.It also can be used for experiments with limited number scans and algorithms not available and/or are of questionable value.Part Three:An Evaluation of Local Glacomatous Damage in the Macula Using Microperimetry,Standard Automated Perimetry, Multifocal Visual Evoked Potential and Frequency Domain Optical Coherence TomographyObjective:To compare the changes of microperimetry,standard automatic perimetry, multifocal visual evoked potential and frequency domain optical coherence tomography in macular damage of glaucoma.To establish a study approach for glaucomatous macular damage and discuss the correlation of structure and function changes in macular area of glaucoma.Methods:Seven eyes of 6 glaucoma patients were included in the study.Humphrey visual field with 24-2 and 10-2 threshold strategy(SITA) was used to test the visual field.Patients had best corrected visual acuity greater than 0.8,spherical refraction within±6.00 diopters and cylinder correction within±2.00 diopters.Normal controls had corrected visual acuity greater than 0.8.Microperimetry was performed on all subjects using the MP-1 Microperimeter.4-2 strategy was used.The stimulus size was GoldmannⅠ.Microperimetry setting was customized using 8×8 grid pattern of 64 stimuli covering 7°.All glaucoma patients underwent the mfVEP using VERIS 5.0 software The dartboard pattern consisted of 60 sectors,each with a checkerboard pattern of 16 checks,8 white (luminance=200 cd/m~2),and 8 black(luminance＜3 cd/m~2).The display had a diameter of 44.6°. All patients and normal controls underwent frequency domain OCT scan.The scan types were macular line scan and 3D scan.Computer assisted segmentation program was used to segment the layers of RNFL,RGC+,INL and total receptor.The thickness of these 4 layers was calculated.Results:RGC+ thickness in patient's group was thinner than controls(p＜0.001).The thickness of RNFL,INL and total retina had no significance.It had good agreement between the structural changes and microperimetry and 10-2 HVF defect around horizontal meridian.Some area showed the structural changes earlier than functional defect.In the comparison between mfVEP and microperimetry,the lower the sensitivity,the lower the mfVEP signal to noise ratio.Compared 10-2 HVF to mfVEP,it also showed the same tendency.In the testing area of microperimetry,the amplitude reduction of the local responses corresponded to the local sensitivity loss well.Conclusions:The approach for study the detailed changes on structure and function in macular is feasible.The changes between structure and function showed good agreement.The objective functional test(mfVEP) confirmed the reliability of the subjective test.The approach provided an effective method to study glaucomatous changes in macular.It is also a useful tool for early diagnosis of glaucoma and monitoring the progression of the disease.