Scanning laser polarimetry with variable and enhanced corneal compensation in normal and glaucomatous eyes

PURPOSE: To investigate whether correction for atypical birefringence pattern (ABP) using scanning laser polarimetry with enhanced corneal compensation (SLP-ECC) reduces the severity of ABP compared with variable corneal compensation (SLP-VCC) and improves the correlation with visual function. DESIGN: Prospective observational study. METHODS: Normal and glaucomatous eyes enrolled from four clinical sites underwent complete examination, automated perimetry, SLP-ECC, and SLP-VCC. Eyes were characterized in three groups based upon the typical scan score (TSS): normal birefringence pattern (NBP) was defined as TSS > or = 80, mild ABP as TSS 61 to 79, and moderate-severe ABP as TSS < or = 60. For each of four SLP parameters, the area under the ROC curve (AUROC) was calculated to compare the ability of SLP-ECC and SLP-VCC to discriminate between normal and glaucomatous eyes. RESULTS: Eighty-four normal volunteers and 45 glaucoma patients were enrolled. Mean TSS was significantly (P < .001) greater using SLP-ECC (98.0 +/- 6.6) compared with SLP-VCC (83.4 +/- 22.5). The frequency of moderate-severe ABP images was significantly (P < .001, McNemar test) higher using SLP-VCC (18 of 129, 14%) compared with SLP-ECC (one of 129, 0.8%). Two SLP-ECC parameters (temporal superior nasal inferior temporal [TSNIT] average and inferior average) had significantly (P = .01, P < .001) higher correlation (r = .45, r = .50, respectively) with MD compared with SLP-VCC (r = .34, r = .37). Among eyes with moderate-severe ABP (n = 18), inferior average obtained using SLP-ECC had significantly (P = .03) greater AUROC (0.91 +/- 0.07) compared with SLP-VCC (0.78 +/- 0.11). CONCLUSIONS: SLP-ECC significantly reduces the frequency and severity of ABP compared with SLP-VCC and improves the correlation between RNFL measures and visual function.     

Scanning laser polarimetry with variable corneal compensation and optical coherence tomography in normal and glaucomatous eyes

PURPOSE: To evaluate the relationship between visual function and retinal nerve fiber layer (RNFL) measurements obtained with scanning laser polarimetry with variable corneal compensation (SLP-VCC) and optical coherence tomography (OCT). DESIGN: Cross-sectional analysis of normal and glaucomatous eyes in a tertiary care academic referral practice. METHODS: A commercial GDx nerve fiber analyzer was modified to enable the measurement of corneal polarization axis and magnitude so that compensation for corneal birefringence was eye specific. Complete examination, SLP with fixed corneal compensation (FCC) and variable corneal compensation (VCC), optical coherence tomography (OCT) imaging of the peripapillary RNFL, and automated achromatic perimetry were performed in all subjects. Exclusion criteria were visual acuity less than 20/40, diseases other than glaucoma, and unreliable perimetry. RESULTS: Fifty-nine patients (59 eyes; 29 normal, 30 glaucomatous) were enrolled (mean age, 56.7 +/- 20.3 years, range, 20-91). All eyes with glaucoma had associated visual field loss (average mean defect, -8.4 +/- 5.8 dB). Using SLP-FCC, nine of 12 retardation parameters (75%) were significantly less in glaucomatous eyes. Using SLP-VCC, 11of 12 retardation parameters (92%) were significantly less in glaucomatous eyes. Multiple regression models constructed for each retardation parameter with visual field demonstrated that the following VCC parameters were statistically significant whereas FCC parameters were not: ellipse average (FCC, P =.28, VCC, P =.001), superior average (FCC, P =.38, VCC, P <.001), inferior average (FCC, P =.10, VCC, P =.008), average thickness (FCC, P =.30, VCC, P =.031), and superior integral (FCC, P =.43, VCC, P =.001). Similar results were obtained for multiple regression models constructed with OCT-derived RNFL thickness: ellipse average (FCC, P =.99, VCC, P =.002), superior average (FCC, P =.90, VCC, P <.001), inferior average (FCC, P =.61, VCC, P =.007), and superior integral (FCC, P =.92, VCC, P <.001). CONCLUSIONS: Compared with fixed compensation, mean-based SLP parameters generated with SLP-VCC have greater correlation with visual function and RNFL thickness assessments obtained with OCT.     

Scanning laser polarimetry with variable corneal compensation in migraine patients

Purpose: This study aimed to compare scanning laser polarimetry measurements of retinal nerve fibre layer (RNFL) thickness in eyes of migraine patients with those in eyes of age‐matched, healthy subjects. Methods: The study was designed as an observational, prospective, cross‐sectional study. It included 57 eyes of 57 patients with migraine with or without aura according to the criteria of the International Headache Society and 44 eyes of 44 age‐matched healthy controls. Scanning laser polarimetry images were obtained using a commercial GDx VCC system (Version 5.3.1; Laser Diagnostic Technologies, Inc.). At each sitting, three sets of GDx VCC measurements were acquired for each patient and used in the analysis. Image acquisition was performed in undilated eyes in all subjects. Results: The mean ± standard deviation RNFL average thickness parameter in the migraine subjects was significantly lower than in the control group, at 50.4 ± 4.8 μm versus 54.7 ± 3.4 μm, respectively (p < 0.0001). However, there were no differences between migraine subjects and controls in mean RNFL thickness in superior and inferior areas. In the migraine group the mean migraine disability assessment (MIDAS) score was 34.3 ± 15.3 and the mean number of attacks per year was 17.1 ± 6.9 (range 6?28). The mean RNFL average thickness parameter was significantly correlated with MIDAS score (r = ? 0.86, p < 0.0001) and frequency of attacks (r = ? 0.86, p < 0.0001). Conclusions: The mean RNFL average thickness parameter was found to be thinner in migraine patients. In addition, we found a strong correlation between migraine severity and RNFL average thickness parameters.     

Scanning laser polarimetry in monkey eyes using variable corneal polarization compensation

PURPOSE: To determine if scanning laser polarimetry (SLP) using variable anterior segment birefringence compensation can provide meaningful retinal nerve fiber layer (RNFL) thickness measurements in monkey eyes. METHODS: A scanning laser polarimeter (GDx; Laser Diagnostic Technologies, San Diego, CA) was modified so that anterior segment birefringence could be compensated on an eye-specific basis. Six eyes of three adult Cynomolgus (Macaca fascicularis) monkeys were imaged. The authors determined the corneal polarization magnitude (CPM) and corneal polarization axis (CPA) in these eyes, and compared them with the fixed values in the commercial scanning laser polarimeter. Individually compensated RNFL images, using eye-specific CPM and CPA, were then obtained to determine if the resulting retardation profiles reflected the expected RNFL appearance observed with stereoscopic optic disc photographs. Two of the imaged monkeys had experimental glaucoma of the right eye, which allowed comparison of RNFL thickness measures between healthy eyes and those damaged by experimental glaucoma. RESULTS: The CPM was small in each of the six eyes examined, ranging from 5.7 to 8.7 nm. The CPA ranged from -62 degrees to 78.7 degrees (nasally upward CPA values were recorded as negative; nasally downward CPA values were recorded as positive). These values are different from the values assumed by the commercially available fixed-compensator GDx. When eye-specific compensation was used, RNFL retardation profiles mimicked the expected appearance of the RNFL in all eyes. The authors also observed a substantial decrease in retardation in experimental glaucoma eyes compared with healthy fellow eyes. CONCLUSIONS: Scanning laser polarimetry using eye-specific corneal polarization compensation can provide meaningful RNFL thickness measurements in monkey eyes. Observed differences in retardation between healthy and experimental glaucoma eyes suggest that SLP may be useful for detecting and monitoring RNFL loss in experimental primate glaucoma.     

Scanning laser polarimetry with enhanced corneal compensation and optical coherence tomography in normal and glaucomatous eyes

PURPOSE: To examine the association between scanning laser polarimetry (SLP), using enhanced (ECC) and variable corneal compensation (VCC) with optical coherence tomography (OCT), and to compare their discriminating ability in the diagnosis of glaucoma. METHODS: Normal and glaucomatous eyes enrolled from four clinical sites underwent complete examination, automated perimetry, SLP-ECC, SLP-VCC, and OCT. Eyes were characterized in two groups based on the typical scan score (TSS): Normal birefringence pattern (NBP) was defined as a TSS of 80 to 100 and abnormal birefringence pattern (ABP) as TSS 相似文献   

Scanning laser polarimetry with variable corneal compensation and optical coherence tomography in tilted disk

PURPOSE: To determine whether scanning laser polarimetry with variable corneal compensation (GDx-VCC) or optical coherence tomography (OCT) is helpful for the analysis of the retinal nerve fiber layer (RNFL) thickness in glaucoma subjects with tilted disk. DESIGN: Retrospective case-control study. METHODS: We included 21 glaucomatous eyes with tilted disk and 35 glaucomatous eyes without tilted disk. Peripapillary RNFL thickness measurement by GDx-VCC and OCT, and also visual field testing with a Humphrey Field Analyzer program 30-2 (HFA) were performed in all subjects. RESULTS: In the group without tilted disk, the RNFL thickness values obtained with GDx-VCC and OCT analysis had a good correlation with mean deviation (MD), and clearly showed stage-dependent reduction. Conversely, in the group with tilted disk, a discrepancy in the RNFL measurement between GDx-VCC and OCT was observed. The correlation of RNFL measurement to the visual field was further examined at each hemifield (superior and inferior). In the group without tilted disk, the measurements of both instruments at each hemifield were in good correlation with the mean pattern deviation values. However, in the group with tilted disk, the GDx-VCC derived values did not correlate with the visual field defect in both hemifields, whereas OCT was in good association with both mean pattern deviation values. Infrared images acquired with a wavelength of nearly 780 nm revealed a high reflex from the sclera in the tilted disk. CONCLUSIONS: Our study has suggested that RNFL analysis by OCT is more suitable for the glaucoma assessment in the tilted disk compared with GDx-VCC.     

Relationship between scanning laser polarimetry with enhanced corneal compensation and with variable corneal compensation

PURPOSE: To evaluate the structure-function relationships between retinal sensitivity measured by Humphrey visual field analyzer (HVFA) and the retinal nerve fiber layer (RNFL) thickness measured by scanning laser polarimetry (SLP) with variable corneal compensation (VCC) and enhanced corneal compensation (ECC) in glaucomatous and healthy eyes. METHODS: Fifty-three eyes with an atypical birefringence pattern (ABP) based on SLP-VCC (28 glaucomatous eyes and 25 normal healthy eyes) were enrolled in this cross-sectional study. RNFL thickness was measured by both VCC and ECC techniques, and the visual field was examined by HVFA with 24-2 full-threshold program. The relationships between RNFL measurements in superior and inferior sectors and corresponding retinal mean sensitivity were sought globally and regionally with linear regression analysis in each group. Coefficients of the determination were calculated and compared between VCC and ECC techniques. RESULTS: In eyes with ABP, R2 values for the association between SLP parameters and retinal sensitivity were 0.06-0.16 with VCC, whereas they were 0.21-0.48 with ECC. The association of RNFL thickness with retinal sensitivity was significantly better with ECC than with VCC in 5 out of 8 regression models between SLP parameters and HVF parameters (P<0.05). CONCLUSIONS: The strength of the structure-function association was higher with ECC than with VCC in eyes with ABP, which suggests that the ECC algorithm is a better approach for evaluating the structure-function relationship in eyes with ABP.     

Scanning laser polarimetry with enhanced corneal compensation for detection of axonal loss in band atrophy of the optic nerve

PURPOSE: To compare the abilities of scanning laser polarimetry (SLP) with enhanced corneal compensation (ECC) and variable corneal compensation (VCC) modes for detection of retinal nerve fiber layer (RNFL) loss in eyes with band atrophy (BA) of the optic nerve. DESIGN: Cross-sectional study. METHODS: Thirty-seven eyes from 37 patients with BA and temporal visual field defect from chiasmal compression and 40 eyes from 40 healthy subjects were studied. Subjects underwent standard automated perimetry and RNFL measurements using an SLP device equipped with VCC and ECC. Receiver operating characteristic (ROC) curves were calculated for each parameter. Pearson correlation coefficients were obtained to evaluate the relationship between RNFL thickness parameters and severity of visual field loss, as assessed by the temporal mean defect. RESULTS: All RNFL thickness parameters were significantly lower in eyes with BA compared with normal eyes with both compensation modes. However, no statistically significant differences were observed in the areas under the ROC curves for the different parameters between GDx VCC and ECC (Carl Zeiss Meditec, Inc, Dublin, California, USA). Structure-function relationships also were similar for both compensation modes. CONCLUSIONS: No significant differences were found between the diagnostic accuracy of GDx ECC and that of VCC for detection of BA of the optic nerve. The use of GDx ECC does not seem to provide a better evaluation of RNFL loss on the temporal and nasal sectors of the peripapillary retina in subjects with BA of the optic nerve.     

Scanning laser polarimetry with variable corneal compensation: identification and correction for corneal birefringence in eyes with macular disease

PURPOSE: In scanning laser polarimetry with variable corneal compensation (SLP-VCC), the macula is used as an intraocular polarimeter to calculate and neutralize corneal birefringence based on an intact Henle's layer. The purpose of this investigation was to validate this strategy in eyes with macular structural disease. METHODS: A nerve fiber analyzer was modified to enable the measurement of corneal polarization axis and magnitude so that compensation for corneal birefringence was eye specific. Normal subjects and patients with a variety of pathologic macular conditions underwent complete ocular examination, SLP-VCC, and direct measurement of the corneal polarization axis (CPA), with a slit-lamp-mounted corneal polarimeter. Macular birefringence patterns were classified as well defined, weak, or indeterminate bow ties. A new "screen" method is described that determines the anterior segment birefringence without relying on the presence of macular bow-tie patterns. RESULTS: Forty-seven eyes (20 normal, 27 with maculopathy) of 47 patients (mean age, 59.0 +/- 19.0 years; range, 24-88) were enrolled. The correlation between CPA measured with corneal polarimetry (CPA by P(IV) [fourth Purkinje image]) and SLP-VCC was less in eyes with macular disease (R(2) = 0.22, P = 0.024) compared with normal eyes (R(2) = 0.72, P < 0.0001). Eyes with macular disease had significantly (P = 0.007) more indeterminate macular bow ties (8/27; 29%) than did normal eyes (0/20). The magnitude of difference between CPA by P(IV) and CPA by SLP-VCC was significantly (P = 0.0007) greater in eyes with indeterminate bow-tie patterns than in weak and well-defined patterns. Although no relationship was observed between CPA and 12 retardation parameters obtained with SLP-VCC in normal eyes (P > 0.05), eyes with macular disease showed a significant association between CPA and average thickness (R(2) = 0.27, P = 0.005), ellipse average (R(2) = 0.24, P = 0.0085), superior average (R(2) = 0.24, P = 0.009), inferior average (R(2) = 0.28, P = 0.004), and superior integral (R(2) = 0.37, P = 0.0008), suggesting incomplete corneal compensation. Greater correlation between CPA by P(IV) and CPA derived by SLP-VCC was found by using the screen method (R(2) = 0.83, P < 0.0001) compared with the bow-tie method (R(2) = 0.22, P = 0.024) in eyes with maculopathy. CONCLUSIONS: Macular strategies for neutralization of corneal birefringence using SLP-VCC can fail if Henle's layer is disrupted by macular disease. The screen method provides a more robust measure of the anterior segment birefringence in some eyes with macular disease.     

Enhanced imaging algorithm for scanning laser polarimetry with variable corneal compensation

PURPOSE: To describe and investigate a method of improving assessment of retinal nerve fiber layer (RNFL) morphology with scanning laser polarimetry (SLP) with variable corneal compensation (VCC). METHODS: By neutralizing anterior segment birefringence with a variable compensator, the current VCC method allows direct measurement of RNFL retardation. In the new method, enhanced corneal compensation (ECC), the variable compensator was set to introduce a "bias" birefringence. This bias was removed mathematically for each individual pixel to produce the RNFL image. In 177 eyes of healthy subjects, patients with glaucoma, and subjects with ocular hypertension, retardation images were obtained with both VCC and ECC. RESULTS: In the tested eyes, images obtained with ECC showed the expected RNFL appearance better than those obtained with VCC. In addition, the typical scan score, which quantifies the amount of atypia, was higher with ECC than with VCC. The amount of residual anterior segment birefringence dropped significantly with ECC in the various groups. Measurements of peripapillary RNFL retardation showed reduced temporal and nasal values with ECC, whereas superior and inferior values were not significantly different between VCC and ECC. The dynamic range appeared to have increased with ECC. The accuracy of the TSNIT (temporal, superior, nasal, inferior, temporal) average and inferior average for detecting glaucoma was higher with ECC than with VCC. CONCLUSIONS: RNFL morphology may be better assessed with the presented ECC method than with standard VCC. ECC may be implemented in the current VCC systems by means of a software upgrade. It may enhance the clinical utility of the GDx VCC in glaucoma management.     

Scanning laser polarimetry with enhanced corneal compensation in patients with open-angle glaucoma

AIMS: To compare the retinal nerve fiber layer thickness (RNFLT) parameters obtained with newly introduced GDx with enhanced corneal compensation (ECC) and those with GDx with variable corneal compensation (VCC) and to evaluate their reproducibility and the correspondence with visual field damage (VFD) in total or sectorized fields in association with refractive errors in open-angle glaucoma (OAG) patients. PATIENTS AND METHODS: Measurement reproducibility was assessed in 30 normal and 30 OAG eyes. Correlation between the RNFLT parameters and the corresponding VFD was evaluated in 58 OAG eyes. RESULTS: All parameters of both GDx VCC and ECC showed high intraclass correlation coefficients among the repeated measurements (0.89 to 0.99), suggesting good reproducibility. All RNFLT parameters were significantly correlated between VCC and ECC (intraclass correlation coefficient=0.58-0.92, P<0.001) though they were significantly different. In OAG eyes, correlation between temporal, superior, nasal, inferior, temporal average and mean deviation of VFD was similar in both algorithms (Rs=0.58 and 0.53, P<0.001). When the OAG eyes were subgrouped by refractive error at -5 D, the correlation was significant for both ECC and VCC in the lower myopic group (>-5 D) (Rs=0.71 and 0.74, P<0.0001) but was significant only for ECC in the higher myopic group (相似文献   

Structure-function relationship is stronger with enhanced corneal compensation than with variable corneal compensation in scanning laser polarimetry

PURPOSE: To compare the structure-function relationship between peripapillary retinal nerve fiber layer (RNFL) retardation, measured with scanning laser polarimetry (SLP) with both enhanced and variable corneal compensation (ECC [enhanced corneal compensation] and VCC [variable corneal compensation], respectively; features of the GDx Nerve Fiber Analyzer; Carl Zeiss Meditec, Inc., Dublin, CA), and visual field (VF) sensitivity, measured with standard automated perimetry (SAP) in normal and glaucomatous eyes and the effect of marked atypical birefringence patterns (ABPs) on this relationship. METHODS: Thirty-three healthy subjects, and 68 patients with primary open-angle glaucoma (POAG) took part in the study. ECC and VCC images were taken in one randomly selected eye of each subject. VF tests were also obtained in the same eyes. The structure-function relationship was assessed in six peripapillary sectors and their matching VF areas and was reassessed after eliminating eyes with marked ABPs. RESULTS: Correlations (Spearman's correlation coefficients, r(s)) in the structure-function relationship were generally stronger in images taken with ECC than in those taken with VCC. With ECC, the relationship was significantly more curvilinear when VF sensitivity was expressed in the standard decibel scale and more linear when VF sensitivity was expressed in an antilog scale than with VCC. When eyes with marked ABP images were removed from the analysis, the structure-function relationship with VCC improved, and no statistically significantly differences were found in the relationships between VCC and ECC. CONCLUSIONS: The structure-function relationship between RNFL retardation and SAP VF sensitivity was stronger in images obtained with the GDx ECC than with the GDx VCC (Carl Zeiss Meditec, Inc., Dublin, CA). ABPs, which appeared more markedly with VCC than with ECC, weakened the structure-function relationship.     

Fourier analysis of scanning laser polarimetry measurements with variable corneal compensation in glaucoma

PURPOSE: To apply Fourier analysis to the retinal nerve fiber layer (RNFL) thickness measurements obtained with scanning laser polarimetry (SLP), by using variable corneal compensation, and to evaluate the ability of this method to discriminate glaucomatous from normal eyes. METHODS: The study included one eye each of 55 patients with glaucoma and 52 healthy subjects. RNFL thickness measurements were obtained with a modified commercial scanning laser polarimeter (GDx Nerve Fiber Analyzer; Laser Diagnostic Technologies, Inc., San Diego, CA) so that corneal birefringence could be corrected on a subject-specific variable basis. The shape of the RNFL thickness double-hump pattern was analyzed by Fourier analysis of polarimetry data. Fourier coefficients and GDx parameters were compared between the two groups. A linear discriminant function was developed to identify and combine the most useful Fourier coefficients to separate the two groups. Receiver operating characteristic (ROC) curves were obtained for each measurement, and sensitivity values (at fixed specificities) were calculated. RESULTS: The Fourier-based linear discriminant function (LDF Fourier) resulted in a sensitivity of 84% for a specificity set at 92%. For similar specificity, the GDx software-provided parameters had sensitivities ranging from 24% to 69%. The area under ROC curve for the LDF Fourier was 0.949, significantly larger than the ROC curve area for the single best GDx software-provided parameter, superior average (0.870). CONCLUSIONS: The combination of Fourier RNFL thickness measures in an LDF, obtained using SLP with variable corneal compensation, improved the ability to discriminate glaucomatous from healthy eyes, compared with the GDx software-provided parameters.     

The effect of atypical birefringence patterns on glaucoma detection using scanning laser polarimetry with variable corneal compensation

PURPOSE: The purpose of this study was to investigate the effect of the presence of atypical birefringence patterns, as measured by the typical scan score (TSS), on the diagnostic accuracy of a scanning laser polarimeter (the GDx VCC; Carl Zeiss Meditec, Inc., Dublin, CA) assessed by receiver operating characteristic (ROC) curves for discriminating between glaucoma and healthy eyes. METHODS: Two hundred thirty-three glaucomatous eyes (repeatable abnormal visual fields by pattern standard deviation [PSD] and/or glaucoma hemifield test [GHT]) from 153 patients with glaucoma and 104 eyes from 71 healthy participants enrolled in the UCSD Diagnostic Innovations in Glaucoma Study (DIGS) were imaged using the GDx VCC. An ROC regression model was used to evaluate the influence of the covariates TSS; disease severity, defined as standard automated perimetry (SAP) mean deviation [MD]; and age in years on the diagnostic accuracy of the GDx parameters nerve fiber indicator [NFI], TSNIT (temporal, superior, nasal, inferior, temporal) average thickness, superior average thickness, inferior average thickness, and TSNIT standard deviation. Areas under the ROC curve were calculated for specific levels of the covariates according to the results provided by the model. RESULTS: TSS and SAP MD significantly affected the diagnostic accuracy of each investigated GDx VCC parameter. Low TSSs, indicating the presence of atypical scans, were associated with decreased accuracy. For NFI, ROC curve areas ranged from 0.749 (when TSS = 20) to 0.904 (when TSS = 100). A similar influence of TSS was found for other parameters. In addition, diagnostic accuracy increased with increasing disease severity. For instance, for NFI, ROC curve areas ranged from 0.853 (when SAP MD = -3) to 0.954 (when SAP MD = -15). CONCLUSIONS: The diagnostic accuracy of GDx VCC parameters is affected by disease severity and is adversely affected by the presence of atypical retardation patterns (i.e., decreasing TSS). GDx VCC scans with atypical scan patterns should be interpreted with caution when used in clinical practice.