Applications of the isolated-check visual evoked potential in primary open angle glaucoma with or without high myopia.

AIM: To explore the diagnostic performance of isolated-check visual evoked potential (icVEP) for primary open angle glaucoma (POAG) in both highly myopic and non-highly myopic populations and compare it with those of optical coherence tomography (OCT) and Heidelberg retinal tomography (HRT) parameters. METHODS: A total of 126 participants were recruited, including 31 highly myopic participants with POAG (HM-POAG), 36 non-highly myopic participants with POAG (NHM-POAG), 25 highly myopic participants without POAG (HM) and 34 controls without high myopia (Normal). All the participants underwent a complete ophthalmic examination. The signal-to-noise ratio (SNR) was used to assess the icVEP. Both qualitative and quantitative diagnostic performances of OCT, HRT and the icVEP were analyzed and compared. RESULTS: Based on the criterion of SNR≤1, the diagnostic performance of the icVEP in highly myopic subjects [area under the receiver operating characteristic curve (AUC)=0.862] was better than that in non-highly myopic subjects (AUC=0.789), and the SNR had fairly good specificity. In distinguishing the HM-POAG and HM groups, the AUC of the SNR was not different from those of the OCT and HRT parameters (P>0.05) in either the qualitative or quantitative comparison. In the qualitative analysis, the icVEP showed good consistency with damage to the central 10° of the visual field (kappa=0.695-0.747, P<0.001). CONCLUSION: The icVEP has the potential to discriminate individuals with and without POAG, especially in populations with high myopia.

Comparison of corneal biomechanics among primary open-angle glaucoma with normal tension or hypertension and controls.

BACKGROUND: Normal tension glaucoma (NTG) is a less pressure-dependent type of glaucoma with characteristic optic neuropathy. Recently, the biomechanical mechanism has been thought to account for glaucomatous optic neuropathy to some degree. We intended to compare dynamic corneal response parameters (DCRs) among patients with primary open-angle glaucoma with normal tension or hypertension and controls. The correlations between DCRs and known risk factors for glaucoma were also analyzed. METHODS: In this cross-sectional study, 49 NTG subjects, 45 hypertension glaucoma (HTG) subjects, and 50 control subjects were enrolled. We compared the differences in DCRs using corneal visualization Scheimpflug technology among the NTG, HTG, and control groups. We also analyzed the correlations between DCRs and known risk factors for glaucoma (eg, central corneal thickness [CCT], intraocular pressure [IOP], etc). RESULTS: The maximum inverse concave radius (NTG: 0.18 [0.17, 0.20] mm-1; control: 0.17 [0.16, 0.18] mm-1; P = 0.033), deformation amplitude ratio of 2 mm (DAR 2 mm, NTG: 4.87 [4.33, 5.39]; control: 4.37 [4.07, 4.88]; P < 0.001), and DAR 1 mm (NTG: 1.62 [1.58, 1.65]; control: 1.58 [1.54, 1.61]; P < 0.001) were significantly higher in NTG than in the controls. The integrated radius (IR, NTG: 8.40 ±â€Š1.07 mm-1; HTG: 7.64 ±â€Š1.31 mm-1; P = 0.026) and DAR 2 mm (NTG: 4.87 [4.33, 5.39]; HTG: 4.44 [4.12, 5.02]; P < 0.007) were significantly higher, whereas the stiffness parameter at the first applanation (SP-A1, NTG: 91.23 [77.45, 107.45]; HTG: 102.36 [85.77, 125.12]; P = 0.007) was lower in NTG than in HTG. There were no significant differences in the DCRs between HTG and control groups (P > 0.05). In the univariate and multivariate analyses, some of the DCRs, such as IR, were negatively correlated with CCT and IOP, whereas SP-A1 was positively correlated with CCT and IOP. CONCLUSIONS: The cornea was more deformable in NTG than in HTG or controls. There were no significant differences in corneal deformability between HTG and controls. The cornea was more deformable with the thinner cornea and lower IOP.

Effectiveness of Glaucoma Diagnostic Parameters from Spectral Domain-Optical Coherence Tomography of Myopic Patients.

BACKGROUND: Currently, spectral-domain optical coherence tomography (SD-OCT) appears to be a new type of glaucoma diagnostic tool. Thus, this study aimed to evaluate the effectiveness of glaucoma diagnostic parameters from SD-OCT of patients with different severities of myopia. METHODS: This was a cross-sectional study. A total of 248 participants (248 eyes) were enrolled, including 51 cases in the early primary open-angle glaucoma group, 79 cases in the control group (0.50 D to -0.50 D, excluding -0.50 D), 47 cases in the low-myopic group (-0.50 to -3.00 D, excluding -3.00 D), 43 cases in the moderate-myopic group (-3.00 to -6.00 D, excluding -6.00 D), and 28 cases in the high-myopic group (≤-6.00 D). All participants were examined using the Humphrey visual field test and SD-OCT. The SD-OCT parameters of the retinal nerve fiber layer (RNFL) and ganglion cell complex were analyzed statistically using the receiver operating characteristic curve and area under the curve (AUC). RESULTS: The AUC showed that the best parameters for the control and low-myopic groups were the inferior and inferior temporal RNFL thicknesses (AUC >0.94), respectively; for the moderate- and high-myopic groups, the best parameter was the temporal low RNFL thickness (AUC, 0.926 and 0.896, respectively). The AUC of the inferior parameters of the moderate-myopic group (0.864) was lower, ranked 15th among all RNFL parameters. When the sensitivity was fixed at 85%, the specificity of the inferior, superior, inferior temporal, and superior temporal quadrants was higher (>80%) in the control and low-myopic groups, while they were lower (20-60%) for the moderate- and high-myopia groups. The green color based on the OCT database was also less for the high-myopic group compared with that of other groups (P < 0.05). CONCLUSIONS: Glaucoma diagnostic parameters from SD-OCT were not clinically effective for the moderate- and high-myopic groups. The specificities were low. The moderate- and high-myopic groups require comprehensive analyses for the diagnoses of glaucoma. The SD-OCT database should be improved to better indicate the level of myopia based on the corresponding diopter readings.

A new diagnostic model of primary open angle glaucoma based on FD-OCT parameters.

AIM: To build a clinical diagnostic model of primary open angle glaucoma (POAG) using the normal probability chart of frequency-domain optical coherence tomography (FD-OCT). METHODS: This is a cross-sectional study. Total 133 eyes from 133 healthy subjects and 99 eyes from 99 early POAG patients were included in the study. The retinal nerve fibre layer (RNFL) thickness parameters of optic nerve head (ONH) and RNFL3.45 scan were measured in one randomly selected eye of each subject using RTVue-100 FD-OCT. Then, we used these parameters to establish the diagnostic models. Four different diagnostic models based on two different area partition strategies on ONH and RNFL3.45 parameters, including ONH traditional area partition model (ONH-T), ONH new area partition model (ONH-N), RNFL3.45 traditional area partition model (RNFL3.45-T) and RNFL3.45 new area partition model (RNFL3.45-N), were built and tested by cross-validation. RESULTS: The new area partition models had higher area under the receiver operating characteristic (AROC; ONH-N: 0.990; RNFL3.45-N: 0.939) than corresponding traditional area partition models (ONH-T: 0.979; RNFL3.45-T: 0.881). There was no statistical difference among AROC of ONH-T, ONH-N, and RNFL3.45-N. Nevertheless, ONH-N was the simplest model. CONCLUSION: The new area partition models had higher diagnostic accuracy than corresponding traditional area partition models, which can improve the diagnostic ability of early POAG. In particular, the simplest ONH-N diagnostic model may be convenient for clinical application.

Corneal Biomechanical Parameters and Asymmetric Visual Field Damage in Patients with Untreated Normal Tension Glaucoma.

BACKGROUND: High intraocular pressure (IOP) and low central corneal thickness (CCT) are important validated risk factors for glaucoma, and some studies also have suggested that eyes with more deformable corneas may be in higher risk of the development and worsening of glaucoma. In the present study, we aimed to evaluate the association between corneal biomechanical parameters and asymmetric visual field (VF) damage using a Corvis-ST device in patients with untreated normal tension glaucoma (NTG). METHODS: In this observational, cross-sectional study, 44 newly diagnosed NTG patients were enrolled. Of these, 31 had asymmetric VF damage, which was defined as a 5-point difference between the eyes according to the Advanced Glaucoma Intervention Study scoring system. Corneal biomechanical parameters were obtained using a Corvis-ST device, such as time from start until the first and second applanation is reached (time A1 and time A2, respectively), cord length of the first and second applanation (length A1 and length A2, respectively), corneal speed during the first and second applanation (velocity A1 and velocity A2, respectively), time from start until highest concavity is reached (time HC), maximum amplitude at the apex of highest concavity (def ampl HC), distance between the two peaks at highest concavity (peak dist HC), and central concave curvature at its highest concavity (radius HC). RESULTS: Time A1 (7.19 ± 0.28 vs. 7.37 ± 0.41 ms, P = 0.010), length A1 (1.73 [1.70-1.76] vs. 1.78 [1.76-1.79] mm, P = 0.007), length A2 (1.58 [1.46-1.70] vs. 1.84 [1.76-1.92] mm, P< 0.001), peak dist HC (3.53 [3.08-4.00] vs. 4.33 [3.92-4.74] mm, P = 0.010), and radius HC (6.20 ± 0.69 vs. 6.59 ± 1.18 mm, P = 0.032) were significantly lower in the worse eyes than in the better eyes, whereas velocity A1 and def ampl HC were significantly higher (0.156 [0.149-0.163] vs. 0.145 [0.138-0.152] m/s, P = 0.002 and 1.19 ± 0.13 vs. 1.15 ± 0.13 mm, P = 0.005, respectively). There was no significant difference in time A2, velocity A2, and time HC between the two groups. In addition, no difference was observed in IOP, CCT, and axial length. In the univariate and multivariate analyses, some of the Corvis-ST parameters, including time A1 and def ampl HC, were correlated with known risk factors for glaucoma, and there was also a significant positive correlation between def ampl HC and age. CONCLUSIONS: There were differences in dynamic corneal response parameters but not IOP or CCT between the paired eyes of NTG patients with asymmetric VF damage. We suggest that the shape of the cornea is more easily altered in the worse eyes of asymmetric NTG patients.

[Prediction of methane emission of paddy field based on the support vector regression model].

The methane emission data of paddy fields was obtained by using the static chamber and gas chromatography, and six parameters including atmospheric temperature, soil temperature at 5 cm depth, pH of soil, Eh of soil, soil moisture and ground biomass were selected as the primary influencing factors of methane emission. The support vector regression (epsilon-SVR) model was built on the optimization of structural risk minimization, and the parameters of the epsilon-SVR model were optimized using Leave-one-out Cross Validation (LOOCV). The prediction accuracy of model was evaluated by k-fold cross validation with the mean relative error (MRE) and the root mean square error (RMSE). In addition, the accuracy of the epsilon-SVR model was analyzed by comparison with the Back Propagation-Artificial Neural Network (BP-ANN) model. The results indicated that the predicted value of the epsilon-SVR model with the parameters C and epsilon optimized by LOOCV was in good agreement with the measured value, and the average MRE of test samples was 44% and the average RMSE was 16.21 mg x (m2 x h)(-1) in the process of 11-fold cross validation. Compared with the BP-ANN model, the correlation coefficient was 0.863, and all the indicators were better. It demonstrated that the 8-SVR model could be applied to the prediction of methane emission of paddy fields.

[Clinical characteristics of eyes with unilateral disc hemorrhage in normal tension glaucoma patients].

OBJECTIVE: To investigate the clinical characteristics of the eyes with unilateral disc hemorrhage (DH) in normal tension glaucoma (NTG) patients. METHODS: 37 normal-tension glaucoma patients with unilateral DH were studied. Extensive parameters were analyzed to evaluate which parameters differ significantly between the DH eyes and the companion eyes. These parameters are: (1) intraocular pressure (IOP), (2) dioptres of refractive errors, (3) central corneal thickness (CCT), (4) disc area, (5) disc shape including horizontal diameter, vertical diameter and horizontal diameter/vertical diameter, (6) global parameters of optic disc, including rim area (G-RA), rim volume (G-RV), mean retinal never fiber layer thickness (G-MRNFLT), cup shape measure (G-CSM) and height variation contour (G-HVC), (7) sectorial parameters of DH located area, including S-RA, S-RV, S-MRNFLT, S-CSM and S-HVC, (8) parameters of the peripapillary atrophy (PPA) beta zone including the incidence rate, area, extent and maximum width. The global and sectorial parameters of the optic disc were obtained directly from HRT-II. The other parameters, such as optic disc horizontal diameter, vertical diameter and PPA, were obtained by processing the raw optic disc images acquired from HRT-II using computer software Image-pro plus version 6. Univariate and multivariate regression analyses were performed on the acquired parameters. RESULTS: The disc vertical diameter (P < 0.01) and incidence rate (P = 0.031) of zone beta appeared to be significantly larger in the DH eyes than the ones in the contra-lateral eyes, while horizontal diameter/vertical diameter was significantly smaller in the DH eyes. As for the optic disc global parameters, the G-MRNFLT (P = 0.028), G-HVC (P = 0.047) were significantly lower in the DH eyes than in the contra-lateral eyes while the G-CSM was significantly higher in DH eyes (P = 0.047). The differences of G-RA, G-RV between two eyes were not significant. As for the regional parameters, S-RA, S-RV, S-MRNFLT were significantly smaller in the DH eyes than in the contra-lateral eyes with P-values 0.033, 0.01 and 0.008 respectively. S-CSM was significantly larger in DH eyes (P = 0.021). S-HVC did not display significant difference between two groups. There were also no significant differences in CCT, dioptres of refractive errors, IOP, PPA parameters (including area, extent and maximum width) between DH eyes and companion eyes. Multivariate regression analysis demonstrated that contained disc area, dioptres of refractive errors, G-RA, G-MRNFLT, G-CSM, horizontal diameter/vertical diameter and zone beta extent, the horizontal diameter/vertical diameter were the significant factors independently associated with disc hemorrhage (P = 0.032, OR < 0.001: < 0.001 - 0.35). Logistic regression analysis also showed that contained disc area, dioptres of refractive errors, S-RA, S-MRNFLT, S-CSM, horizontal diameter/vertical diameter and zone beta extent, the horizontal diameter/vertical diameter and S-MRNFLT were the significant factors independently associated with disc hemorrhage (S-MRNFLT: P = 0.019, OR < 0.001: < 0.001 - 0.154; horizontal diameter/vertical diameter: P = 0.02, OR < 0.001: < 0.001 - 0.124). CONCLUSION: Our study indicates that horizontal diameter/vertical diameter is significantly smaller in NTG patients with unilateral optic disc hemorrhages. The DH located area also appears to have thinner RNFL thickness. Unilateral optic disc hemorrhages tend to have severe RNFL damage in DH located area and their optic disc shape tend to be longer, therefore we hypothesis that the elongation of the optic disc may be associated with the occurrence of DH.

Diagnostic capability of Fourier-Domain optical coherence tomography in early primary open angle glaucoma.

BACKGROUND: Optical coherence tomography (OCT) is a high resolution noncontact imaging modality which can quantitatively detect the optic disc and retinal structure. This study was designed to evaluate the diagnostic capability of parameters of the optic disc, retinal nerve fiber layer thickness, and ganglion cell complex (GCC) using a new technology called Fourier-domain OCT (FD-OCT) for early primary open angle glaucoma (POAG) patients. METHODS: Two groups of patients, early perimetric damage POAG and normal subjects were included in this observational cross-sectional study. All patients underwent FD-OCT and visual field examination in addition to full ophthalmic examinations. Receiver operating characteristic curves (ROC) were studied for all parameters. The sensitivity and specificity for distinguishing between normal and early glaucomatous eyes, the areas under the receiver operating characteristic curves (AROC) and positive, negative likelihood ratios were evaluated for all the single parameters and selected combined parameters using arbitrary cutoffs. RESULTS: Thirty-four eyes of 34 early POAG patients and 42 eyes of 42 normal subjects were analyzed. Cup/disc (C/D) vertical ratio presented the best sensitivity and positive likelihood ratio for selected specificities (95% and 85%) which were 79.4% and 88.2%, 33.4 and 7.4, respectively. Among all single parameters, the C/D vertical ratio demonstrated the highest AROC which was at 0.930. The average thickness of circumpapillary RNFL on 3.45 mm showed the highest AROC among all of the peripapillary RNFL parameters. The sensitivity at selected specificity and AROC of GCC were not as high as C/D vertical ratio and RNFL AT on 3.45 mm. When the C/D vertical ratio, RNFL AT on 3.45 mm, and rim area were combined using a logistical diagnostic model, the AROC was raised to 0.949 but not significantly different from the top single parameter, C/D vertical ratio. CONCLUSIONS: The key parameters obtained by FD-OCT were able to show the significant differences of optic discs, thickness of RNFL and GCC between POAG patients and normal subjects. According to sensitivity, specificity, likelihood ratio and AROC, the top three parameters from FD-OCT for early diagnosis of POAG were C/D vertical ratio, RNFL AT on 3.45 mm, and the rim area.

[Effect of fundus image devices for early diagnosis of primary open angle glaucoma].

Evaluation of the optic disc and retinal nerve fiber layer measurements (RNFL) with stereophotography is the current "gold standard" for the diagnosis of early primary open angle glaucoma (POAG), but it is still subjective and is dependent too much upon an experienced observer. Substantial variability exists in the interpretation of optic disc change over time. There are consistent evidences that image analysis devices such as optical coherence tomography (OCT) and Heidelberg retina tomograph (HRT-II) can detect early to moderate glaucoma as well as expert assessment of stereoscopic optic disc and RNFL photographs. Optic disc and RNFL defect can be quantitatively measured by these devices. But the sensitivity and specificity of the measurements obtained with these devices are not good enough for the early diagnosis of POAG at this time due to several reasons, such as individual variety of the structure parameters in normal subjects, lack of powerful normative database, lack of diagnostic parameters which are good enough both in sensitivity and specificity for detecting early glaucoma damage. However, information obtained from these image analysis devices might be helpful in early POAG diagnosis if clinicians can understand the advantages and limitations of these instruments.

[Comparison of peripapillary atrophy in eyes with unilateral visual field defect in patients with primary open-angle glaucoma and normal tension glaucoma].

OBJECTIVE: To evaluate the difference of the peripapillary atrophy between two eyes of unilateral visual field defect in each of patient with primary open-angle glaucoma (POAG) and normal tension glaucoma (NTG). METHODS: This study included 40 eyes with unilateral visual field defect in patients with POAG (20 cases) and NTG (20 cases). Color stereo optic disc photographs were morphometrically evaluated by a video camera and a computer system. The refractive range (spherical equivalent) of all these subjects was between -3.00D and +3.00D. RESULTS: The cup areas (CA) and cup/disc areas (CA/DA) in eyes with visual field defect were significantly larger than in eyes with normal visual field (CA: t=5.332, P<0.01; CA/DA: t=5.126, P<0.01). The alpha zone areas (alphaA) of PPA were significantly enlarged in visual field defect eyes compared with visual field normal eyes (t=3.02, P=0.0045), while there is no significant difference in beta-zone area (betaA) between two eyes. (S=13.5, P=0.426). The frequency of the PPA (alpha-zone and beta-zone) occurrence were also similar in both eyes. (alphaA: chi(2)=0.00, P=1.000; betaA: chi(2)=1.2857, P=0.2568). CONCLUSION: The results suggest that either beta-zone area or the presence of PPA is not closely correlated to the visual field defect in POAG and NTG patients with exclusion of moderate or high myopia.

[Peripapillary atrophies in primary open-angle glaucoma and glaucoma-like normal disks].

OBJECTIVE: To evaluate the variety of peripapillary atrophy (PPA) and its relationship with visual field among primary open angle glaucoma (POAG), normal tension glaucoma (NTG), and normal subjects with glaucoma-like disk (GLD) that had no evidence of visual field defect and retinal nerve fiber layer defect. METHODS: The study included 42 eyes of 42 patients with POAG, 40 eyes of 40 patients with NTG, and 45 eyes of normal subjects with GLD. Stereo color optic disc photographs were morphometrically evaluated by a video camera and computer system. The refractive range ( spherical equivalent) of all these subjects was between + 3.00D and -3.00D. RESULTS: The alpha-zone and beta-zone of PPA occurred significantly (P <0. 05) more frequent in both patients with POAG( 100. 0% ,48. 9% )and with NTG(95.0% ,37. 5% )than that of normal subjects with GLD(85.4% ,19. 1% ) , but no difference was found between the POAG and NTG groups (P > 0. 05). The beta-zone area of PPA was significantly ( P < 0. 05) enlarged in POAG compared with GLD normal subjects. While there is no significant difference in alpha-and beta-zone area between all other groups. In glaucoma patients, The alpha-zone or the beta-zone area of PPA weakly correlated with the glaucomatous visual field defect While cup/disk area ratio showed a relatively strong correlation. Cup/disc area ratio and age were the only two risk factors for the occurrence of glaucomatous visual field defect among all the factors including PPA by logistic regression analysis. CONCLUSIONS: Our results demonstrate that cup/disc area ratio is well correlated with glaucomatous visual field defect. The occurrence of alpha-zone, beta-zone, and beta-zone areas of PPA may not be a clinically useful parameter, for diagnosing or differentiating POAG and NTG .