Comparative study of retinal nerve fiber layer measurement by StratusOCT and GDx VCC, I: correlation analysis in glaucoma

PURPOSE: To evaluate the average and regional correlations of retinal nerve fiber layer (RNFL) thickness measured by StratusOCT (optical coherence tomography; Carl Zeiss Meditec, Inc., Dublin, CA) and GDx VCC (Laser Diagnostic Technologies, Inc., San Diego, CA). METHODS: Eighty-nine subjects-27 normal, 21 with suspected glaucoma, and 41 with glaucoma-were included in this cross-sectional study. The total average and the mean 12-clock-hour RNFL thickness were measured with the StratusOCT and GDx VCC. The discriminating powers of the two techniques for detection of suspected glaucoma and glaucoma were compared by the area under the receiver operating characteristic curves (AUC). Correspondence between StratusOCT and GDx VCC RNFL measurements in each clock hour was examined with linear regression analysis. RESULTS: The average RNFL thickness in the normal group was measured at 101.38 +/- 7.73 and 55.26 +/- 4.32 mum by StratusOCT and GDx VCC, respectively. Both nerve fiber analyzers demonstrated a double-hump pattern in the RNFL profiles with maximum RNFL thickness located at the inferotemporal and superotemporal clock hours by the StratusOCT and the superior and inferior clock hours by the GDx VCC. Significant differences were found in the total average and the individual clock-hour RNFL thickness between StratusOCT and GDx VCC RNFL measurements in both the normal and the suspected glaucoma/glaucoma groups. The GDx VCC superior RNFL measurement demonstrated the largest AUC (0.909) for detection of suspected glaucoma and glaucoma, whereas the largest AUC (0.901) in StratusOCT was found over the inferotemporal clock hour. The total average RNFL thickness measured with StratusOCT and GDx VCC correlated highly with each other (r = 0.852). When the respective clock-hour RNFL measurements were compared, the correlation coefficient varied with the position around the optic nerve head, with the highest correlation found over the superior and inferior clock hours (11, 12, 1, 6, and 7 o'clock; all with r > 0.700) and the lowest located at the temporal clock hour (9 o'clock; r = 0.277). CONCLUSIONS: Despite the substantial differences in the values of RNFL thickness, significant correlations were observed between StratusOCT and GDx VCC RNFL measurements. The variations of the correlation coefficient around the optic nerve head suggested that GDx VCC RNFL measurement does not have a fixed relationship with that of StratusOCT and the use of site-specific RNFL birefringences may improve the estimation of RNFL thickness by the GDx VCC. Nevertheless, the GDx VCC was found to be as effective as the StratusOCT in detecting the loss of RNFL in glaucoma.     

Relación entre la perimetría automatizada convencional y los parámetros de la capa de fibras nerviosas de la retina obtenidos con la polarimetría láser

PurposeTo determine the relationship between the structural parameters of the retinal nerve fiber layer (RNFL) obtained by using the scanning laser polarimetry with variable corneal compensation (GDx VCC) and the results of standard automated perimetry (SAP), in normal, ocular hypertensive, preperimetric glaucomas and glaucoma subjects.MethodsA total of 423 eyes of 423 consecutive subjects were prospectively included in the study and classified depending on the basal intraocular pressure, optic nerve head appearance and SAP results into four groups: 87 normal eyes, 192 ocular hypertensive eyes, 70 preperimetric glaucomas and 74 glaucomatous eyes. Pearson's correlation coefficients, between mean deviation (MD), pattern standard deviation, number of points altered in each quadrant, and number of points altered at different probability levels of SAP and structural parameters of RNFL obtained by using GDx VCC, were calculated in the different diagnostic groups. In the glaucoma group correlations between the 52 points tested by 24-2 SITA standard and GDx parameters were also calculated. Regression curves were plotted for the strongest correlations.ResultsWeak or non-significant correlations were found in the normal, ocular hypertensive and preperimetric glaucoma groups. However, the glaucoma group presented weak to moderate correlations between several GDx VCC parameters and the SAP variables analysed. The strongest correlation was observed between the standard deviation TSNIT and the MD (0.460).ConclusionsRNFL parameters measured with the GDx VCC presented weak to moderate correlations with the visual field indices and the number of altered points in the glaucoma group.     

Visualization of localized retinal nerve fiber layer defects with the GDx with individualized and with fixed compensation of anterior segment birefringence

PURPOSE: To compare the visualization of localized retinal nerve fiber layer (RNFL) defects in GDx images with fixed and with individualized compensation of anterior segment birefringence (FC and IC, respectively) with their visualization in red-free fundus photographs. DESIGN: Observational case series. PARTICIPANTS: Eight eyes of six glaucoma patients with localized, wedge-shaped RNFL defects in red-free fundus photographs with matching visual field defects. METHODS: We imaged all eyes with a GDx equipped with a variable corneal compensator (VCC). The VCC replaced the standard fixed compensator and could be set to compensate for birefringence of up to 120 nm at any axis. Individual anterior segment birefringence was estimated from a macular retardation profile that resulted from the interaction between birefringence of the anterior segment and that of Henle's fiber layer. Measurements of RNFL retardation were made with the GDx with FC (60 nm of retardation with a slow axis of 15 degrees nasally downward) and with IC. Maps of retardation measurements with FC and IC were superimposed on red-free fundus photographs. MAIN OUTCOME MEASURES: Visualization of localized RNFL defects. RESULTS: Localized RNFL defects were visible in GDx retardation maps obtained with IC. The defects closely matched those observed in red-free fundus photographs. With FC, however, the GDx retardation images did not correlate well with red-free fundus photography. CONCLUSIONS: An individualized anterior segment compensation in the GDx improves the visualization of localized glaucomatous loss.     

Can frequency-doubling technology and short-wavelength automated perimetries detect visual field defects before standard automated perimetry in patients with preperimetric glaucoma?

PURPOSE: To assess the ability of frequency-doubling technology (FDT) perimetry and short-wavelength automated perimetry (SWAP) to detect glaucomatous damage in preperimetric glaucoma subjects. PARTICIPANTS: Two hundred seventy-eight eyes of 278 subjects categorized as normal eyes [n=98; intraocular pressure <20 mm Hg, normal optic disc appearance, and standard automated perimetry (SAP)]; preperimetric glaucoma eyes (n=109; normal SAP and retinal nerve fiber layer defects or localized optic disc notching and thinning); and glaucoma patients (n=71; intraocular pressure >21 mm Hg, optic disc compatible with glaucoma, and abnormal SAP). METHODS: The preperimetric glaucoma group underwent at least 2 reliable full-threshold 24-2 Humphrey SAPs, full-threshold C-20 FDT, full-threshold 24-2 SWAP, optic disc topography using the Heidelberg Retina Tomograph II, laser polarimetry using the GDx VCC, and Optical Coherence Tomography (Zeiss Stratus OCT 3000). Receiver operating characteristic curves were plotted for the main Heidelberg Retina Tomograph, Optical Coherence Tomography, and GDx VCC parameters for the normal and glaucoma patients. The area under the receiver operating characteristic curve was used to determine the parameters indicating glaucomatous damage in the optic disc or retinal nerve fiber layer, which were used to establish additional subgroups of patients with preperimetric glaucoma. FDT and SWAP sensitivities were calculated for the patient subsets with structural damage and normal SAP. RESULTS: At least 20% of the patients with preperimetric glaucoma demonstrated functional losses in FDT and SWAP. The more severe the structural damage, the greater the sensitivity for detecting glaucomatous visual field losses. CONCLUSIONS: FDT and SWAP detect functional losses in cases of suspected glaucoma before glaucomatous losses detected by SAP.     

Comparison of the GDx VCC scanning laser polarimeter and the stratus optical coherence tomograph in the detection of band atrophy of the optic nerve

AIM: To compare the ability of scanning laser polarimeter (SLP) with variable corneal compensation (GDx VCC) and optical coherence tomograph (Stratus OCT) to discriminate between eyes with band atrophy (BA) of the optic nerve and healthy eyes. METHODS: The study included 37 eyes with BA and temporal visual field (VF) defects from chiasmal compression, and 29 normal eyes. Subjects underwent standard automated perimetry (SAP) and retinal nerve fibre layer (RNFL) scans using GDx VCC and Stratus OCT. The severity of the VF defects was evaluated by the temporal mean defect (TMD), calculated as the average of 22 values of the temporal total deviation plot on SAP. Receiver operating characteristic (ROC) curves were calculated. Pearson's correlation coefficients were used to evaluate the relationship between RNFL thickness parameters and the TMD. RESULTS: No significant difference was found between the ROC curves areas (AUCs) for the GDx VCC and Stratus OCT with regard to average RNFL thickness (0.98 and 0.99, respectively) and the superior (0.94; 0.95), inferior (0.96; 0.97), and nasal (0.92; 0.96) quadrants. However, the AUC in the temporal quadrant (0.77) was significantly smaller (P<0.001) with GDx VCC than with Stratus OCT (0.98). Lower TMD values were associated with smaller RNFL thickness in most parameters from both equipments. CONCLUSION: Adding VCC resulted in improved performance in SLP when evaluating eyes with BA, and both technologies are sensitive in detecting average, superior, inferior, and nasal quadrant RNFL loss. However, GDx VCC still poorly discriminates RNFL loss in the temporal quadrant when compared with Stratus OCT.     

Optic disk and nerve fiber layer imaging to detect glaucoma

PURPOSE: To compare optic disk and retinal nerve fiber layer (RNFL) imaging methods to discriminate eyes with early glaucoma from normal eyes. DESIGN: Retrospective, cross-sectional study. METHODS: In a tertiary care academic glaucoma center, 92 eyes of 92 subjects (46 with early perimetric open-angle glaucoma and 46 controls) were studied. Diagnostic performance of optical coherence tomography (StratusOCT; Carl Zeiss Meditec, Dublin, California, USA), scanning laser polarimetry (GDx VCC; Laser Diagnostic Technologies, San Diego, California, USA), confocal laser ophthalmoscopy (Heidelberg Retinal Tomograph [HRT] III; Heidelberg Engineering GmbH, Heidelberg, Germany), and qualitative assessment of stereoscopic optic disk photographs were compared. Outcome measures were areas under receiver operator characteristic curves (AUCs) and sensitivities at fixed specificities. Classification and regression tree (CART) analysis was used to evaluate combinations of quantitative parameters. RESULTS: The average (+/- standard deviation) visual field mean deviation for glaucomatous eyes was -4.0 +/- 2.5 dB (decibels). Parameters with largest AUCs (+/- standard error) were: average RNFL thickness for StratusOCT (0.96 +/- 0.02), nerve fiber indicator for GDx VCC (0.92 +/- 0.03), Frederick S. Mikelberg (FSM) discriminant function for HRT III (0.91 +/- 0.03), and 0.97 +/- 0.02 for disk photograph evaluation. At 95% specificity, sensitivity of disk photograph evaluation (90%) was greater than GDx VCC (P = .05) and HRT III (P = .002) results, but not significantly different than those of StratusOCT (P > .05). The combination of StratusOCT average RNFL thickness and HRT III cup-to-disk area with CART produced a sensitivity of 91% and specificity of 96%. CONCLUSIONS: StratusOCT, GDx VCC, and HRT III performed as well as, but not better than, qualitative evaluation of optic disk stereophotographs for detection of early perimetric glaucoma. The combination of StratusOCT average RNFL thickness and HRT III cup-to-disk area ratio provided a high diagnostic precision.     

Diabetes-associated retinal nerve fiber damage evaluated with scanning laser polarimetry

PURPOSE: To evaluate retinal nerve fiber layer (RNFL) thickness in patients with diabetes mellitus compared with age-matched normal control subjects, to assess the correlation between the RNFL thickness and the severity of retinopathy, and to investigate whether diabetes mellitus is a potential source of abnormal results in glaucoma screening or evaluation with scanning laser polarimetry (SLP). DESIGN: Cross-sectional analysis of normal and diabetic eyes. METHODS: setting: Institutional clinical study. patients: One hundred twenty-eight subjects with type 2 diabetes mellitus and 50 age-matched normal control subjects without glaucoma or glaucoma-suspect. All patients underwent imaging with SLP and repeatable automated perimetry. Subjects with diabetes mellitus were classified into four stages on the basis of the severity of retinopathy that was assessed by dilated funduscopic examination, high-quality fundus color photography, and fluorescein angiography. MAIN OUTCOME MEASURES: The SLP (GDx VCC software, version 5.5.0) parameters. RESULTS: The RNFL thickness in patients with diabetes mellitus was reduced significantly compared with age-matched normal control eyes (P < .01). Moreover, all RNFL thickness parameters of the GDx VCC software decreased significantly as an exacerbation of diabetic retinopathy (P = .0019, P = .0045, P = .0010 for temporal-superior-nasal-inferior-temporal (TSNIT) average, superior average, inferior average, respectively). The nerve fiber indicator also increased significantly (P < .0001), despite an absence of glaucomatous optic nerve damages. CONCLUSION: The RNFL thickness in type 2 diabetes mellitus, which was measured by GDx VCC software, significantly decreased with the severity of diabetic retinopathy. The presence of diabetes mellitus can be a source of false-positive results and overestimation of glaucomatous optic neuropathy when eyes are screened with GDx VCC software.     

Effect of change in macular birefringence imaging protocol on retinal nerve fiber layer thickness parameters using GDx VCC in eyes with macular lesions

This study evaluates the effect of two macular birefringence protocols (bow-tie retardation and irregular macular scan) using GDx VCC on the retinal nerve fiber layer (RNFL) thickness parameters in normal eyes and eyes with macular lesions. In eyes with macular lesions, the standard protocol led to significant overestimation of RNFL thickness which was normalized using the irregular macular pattern protocol. In eyes with normal macula, absolute RNFL thickness values were higher in irregular macular pattern protocols with the difference being statistically significant for all parameters except for inferior average thickness. This has implications for monitoring glaucoma patients who develop macular lesions during the course of their follow-up.     

The relationship between optical coherence tomography and scanning laser polarimetry measurements in glaucoma

PURPOSE: To investigate the relationship between optical coherence tomography (OCT) and scanning laser polarimetry (SLP) in measuring peripapillary retinal nerve fiber layer (RNFL) thickness in glaucomatous eyes. METHODS: Fifty glaucomatous eyes were evaluated in this study. Evaluations were analyzed two ways. First, parameters of the Stratus OCT (average thickness, superior/inferior average) and GDx VCC (TSNIT average, nerve fiber indicator (NFI), superior/inferior average) were correlated using the Pearson's correlation coefficient (r). Secondly, comparison (r) of these parameters was completed using the mean deviation (MD) of visual field defect. RESULTS: The following parameters were found to be significantly correlated (P < 0.005). TSNIT average/average thickness (r = 0.673), NFI/average thickness (r = -0.742), superior average (r = 0.841), and inferior average (r = 0.736). In the correlation analysis using the severity of visual field defect, all these parameters had statistically meaningful correlations (P < 0.005). CONCLUSIONS: GDx VCC and Stratus OCT are highly correlated in glaucomatous eyes. Therefore, peripapillary RNFL thickness measured by Stratus OCT and GDx VCC may be equally helpful in the diagnosis of glaucoma.     

频域OCT检测视野前青光眼黄斑区视网膜神经节细胞复合体厚度的初步研究

Objective To evaluate the diagnostic capabilities of ganglion cell complex (GCC) thickness in preperimetric glaucoma (PPG) with spectral domain optical coherence tomography (SD-OCT). Design Self control study and case control study. Participants Primary open-angle glaucoma (POAG) patients were 20 cases(40 eyes), of which 20 eyes without visual field defects as PPG, and healthy controls were 30 cases(30 eyes). Methods All subjects were underwent macular scanning and peripapillary retinal nerve fiber layer (RNFL) scanning using the RTvue SD-OCT. The area under the receiver operating characteristic curve (AUC) was used to assess the ability to discriminate PPG from normal control. Main Outcome Measures The thickness of GCC and RNFL, and their AUCs. Results Compared with normal eyes, the thickness of average GCC, superior GCC, inferior GCC, average RNFL, superior RNFL, and inferior RNFL in PPG eyes decreased (P<0.001). However, these parameters were thicker than POAG eyes (P≤0.002). The values of GCC-GLV and GCC-FLV increased compared with normal eyes (P<0.001, P=0.021), but decreased compared with POAG eyes (P<0.001). GCC-GLV had highest AUC for detecting PPG (0.983) from normal eyes, followed by average RNFL (0.930). However, the difference between the two parameters was not statistically significant (P>0.05). Conclusions In addition to RNFL, the GCC could be a structural parameter for detecting PPG. (Ophthalmol CHN, 2017, 26: 10-14)     

Use of progressive glaucomatous optic disk change as the reference standard for evaluation of diagnostic tests in glaucoma

PURPOSE: Progressive change in optic disk appearance has been suggested as the best available reference standard for glaucoma diagnosis. We evaluated the accuracy of scanning laser polarimetry (SLP) with variable corneal compensation to discriminate patients with documented progressive optic disk change from healthy subjects. DESIGN: Observational case-control study. METHODS: Glaucoma patients with documented evidence of progressive optic disk change as assessed by stereoscopic photographs were selected. Healthy control subjects had normal visual fields and normal clinical examination. All subjects underwent imaging with the GDx VCC scanning laser polarimeter. Receiver-operating characteristic (ROC) curves, sensitivities at fixed specificities, and likelihood ratios were calculated. RESULTS: Sixty-five eyes were healthy control patients. Seventy-one eyes had progressive optic disk change, of which 41 (58%) had abnormal visual field tests closest to the imaging date (perimetric glaucomatous optic neuropathy [GON]), and 30 (42%) eyes had normal visual fields (preperimetric GON). The GDx VCC parameter nerve fiber indicator performed best for discrimination between perimetric GON and normal eyes (AUC = 0.94; sensitivity = 93% for specificity > or =80%) as well as for the discrimination between preperimetric GON and normal eyes (AUC = 0.89; sensitivity = 83% for specificity > or =80%). CONCLUSION: SLP differentiated patients with documented progressive optic disk change from normal subjects and detected abnormalities in patients with confirmed diagnosis of preperimetric GON, suggesting that it may be useful for early glaucoma diagnosis. We suggest that progressive optic disk change should be used in the evaluation of diagnostic accuracy of imaging instruments for glaucoma.     

Blue-on-yellow perimetry and optical coherence tomography in patients with preperimetric glaucoma

Purpose: To investigate the diagnostic ability of blue‐on‐yellow perimetry (B/YP) and Stratus optical coherence tomography (OCT) in discriminating preperimetric glaucoma from normal eyes. Methods: A total 40 eyes of 40 normal subjects, 38 eyes of 38 preperimetric glaucoma patients (normal standard automated perimetry [SAP] and retinal nerve fibre layer [RNFL] defects or localized optic disc notching and thinning) were enrolled in the study. All the patients underwent SAP and B/YP tests, and OCT measurements. The correlation between B/YP indices and OCT parameters in the eyes with preperimetric glaucoma was analysed. Receiver operating characteristic (ROC) curve area was calculated to discriminate preperimetric glaucoma from normal eyes. Results: In preperimetric glaucoma, 42% eyes (16/38) had B/YP visual field loss, and 68% eyes (26/38) had RNFL defects with OCT measurements. A mild significant correlation was found between B/YP pattern standard deviation (PSD) and average RNFL thickness (Avg.Thi) (R² = 0.112, P = 0.012), superior maximum (Smax) (R² = 0.140, P = 0.005) and maximum‐minimum (Max‐Min) (R² = 0.074, P = 0.042) in the preperimetric glaucoma group. The areas under the ROC curve for B/YP PSD and B/YP mean deviation were 0.721 and 0.665, respectively, and the three OCT parameters with the widest areas under the ROC curve were Avg.Thi (0.719), inferior average (Iavg) (0.718) and nasal average (Navg) (0.706). The highest sensitivity of the individual B/YP indices and OCT parameters for detection of preperimetric glaucoma was B/YP mean deviation (32%) and Smax/Navg (40%) at 90% specificity; the highest sensitivity of the individual B/YP indices and OCT parameters was B/YP PSD (49%) and Iavg (56%) at 80% specificity. Conclusion: The sensitivity of B/YP indices and Stratus OCT RNFL thickness parameters is low for detecting preperimetric glaucoma, suggesting that BYP and OCT as utilized in this study have limited utility in the detection of preperimetric glaucoma.     

The retinal nerve fiber layer in normal eyes and in glaucoma. I. Semiquantitative data of 398 eyes with glaucoma

Atrophy of the optic nerve is associated with changes of the retinal fiber layer (RNFL). Using red-free photographs the authors examined the RNFL of 398 eyes with chronic primary open-angle glaucoma and compared it with the RNFL of 234 normal eyes. The glaucoma group was divided into five stages and the fundus into four sectors. Differences between the normal and glaucoma eyes were: (1) The sequence of the sectors, with regard to the best visibility of the retinal nerve fiber bundles, was changed. In the normal eyes the nerve fiber bundles were most often best visible in the inferior temporal sector, followed by the superior temporal sector, the temporal horizontal area and finally the nasal region. In the glaucoma group the nerve fiber bundles were significantly more often best detectable in the superior temporal sector and the temporal horizontal area. (2) The degree of visibility of the retinal nerve fibers decreased significantly with increasing glaucoma stage. (3) Localized defects were seen in 15% of the eyes with glaucoma and none of the normal eyes. The specificity of this qualitative parameter was, therefore, 100%. The defects were found most often in the superior and inferior temporal regions. These differences between normal and glaucomatous eyes were also significant for the first glaucoma stage of this study. The localization of the foveola below the optic disk center (0.53 +/- 0.34 mm in the glaucoma group and 0.55 +/- 0.29 mm in the normal eyes) was not significantly different.     

Diagnostic value of GDx polarimetry in a Taiwan Chinese population.

PURPOSE: To study the diagnostic ability of scanning laser polarimetry with variable corneal compensation (GDx VCC) for early glaucomatous (EG) eyes and glaucoma-suspect (GS) eyes in a Taiwan Chinese population. METHODS: This prospective cross-sectional study included 82 EG eyes (mean deviation, MD: -3.32 +/- 2.20 dB), 45 GS eyes (MD: -2.43 +/- 2.16 dB), and 62 normal eyes. Retinal nerve fiber layer thickness of each subject was measured using GDx VCC and Humphrey Field Analyzer visual field testing. Measured GDx VCC parameters were compared among groups. The area under the receiver operating characteristic (AROC) curve of each parameter was used to differentiate normal from EG eyes or GS eyes. The correlation between MD and each parameter was also evaluated. RESULTS: For both normal versus EG and normal versus GS, the largest AROC values were for nerve fiber indicator, superior average thickness, and inferior average thickness. There was no significant correlation between MD and GDx-VCC-measured parameters either in EG or GS eyes. CONCLUSIONS: GDx VCC shows only moderate ability to distinguish normal eyes from eyes with early glaucoma. However, its diagnostic role in eyes with suspicious discs and normal visual fields is uncertain at this moment in the Taiwan Chinese population. Further studies are needed to address this issue.     

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 versus frequency-doubling perimetry and conventional threshold perimetry: changes during a 12-month follow-up in preperimetric glaucoma. A pilot study.

PURPOSE: To evaluate the possibility for detecting the progression in preperimetric primary open angle glaucoma (POAG) using scanning laser polarimetry (SLP), frequency-doubling technology (FDT), and conventional automated perimetry (AP). PATIENTS AND METHODS: 22 eyes of 11 preperimetric POAG patients were evaluated using SLP (Nerve Fiber Analyzer, GDx), AP (Humphrey 24-2 threshold test) and FDT (30 degrees threshold test). All eyes had intraocular pressure (IOP) higher than 21 mmHg before treatment, but were consistently lower than 22 mm Hg with unchanged topical medication before and during the study. At the initial evaluation session optic nerve heads showed mild glaucomatous changes but the visual fields were normal (MD better than 2.0 dB, Glaucoma Hemifield Test: within normal limits or borderline). AP and FDT measurements were repeated 6 months later, and all three tests were repeated 12 months after the first investigation. RESULTS: IOP, AP and FDT measurements showed no statistically significant changes during the 12-month follow up period. In contrast to this, a tendency for a glaucomatous type decrease was seen with SLP in the retinal nerve fibre layer (RNFL) thickness parameters (mean superior and inferior sector thickness values, ellipse average thickness and maximal modulation). The mean decrease of RNFL thickness in the superior and inferior sectors was 2.77 microm and 2.48 microm, respectively. Using the two-way nested ANOVA, which considers the relation between the right and left eyes of the subjects, the decrease was statistically significant (p=0.021) for the inferior sector RNFL thickness. CONCLUSION: The results suggest that scanning laser polarimetry is a useful technique to detect and measure glaucomatous progression in early glaucoma. Scanning laser polarimetry of the RNFL may help to detect and quantify early progression even if worsening is not seen with perimetry and FDT tests.     

Structural and Functional Relationships in Glaucoma Using Standard Automated Perimetry and the Humphrey Matrix

Purpose

To evaluate and compare correlations between structural and functional loss in glaucoma as assessed by optical coherence tomography (OCT), scanning laser polarimetry (GDx VCC, as this was the model used in this study), standard automated perimetry (SAP), and the Humphrey Matrix (Matrix).

Methods

Ninety glaucomatous eyes identified with SAP and 112 eyes diagnosed using Matrix were independently classified into six subgroups, either S1/M1 (MD>-6dB), S2/M2 (-12ResultsIn the SAP subgroups, RNFL thickness values obtained by OCT in the nasal and temporal quadrants and the inferior averages of GDx VCC did not differ between the S1 and S2 subgroups (p=0.137, 0.738 and 0.149, respectively). In the Matrix subgroups, no measurement parameters differed between the M1 and M2 groups except for the overall mean and average inferior RNFL thickness given by OCT and the NFI values of GDx VCC (p=0.013, 0.016 and 0.029, respectively). When abnormal classifications were compared, all measurement parameters, without exception, were significantly different in both the SAP and the Matrix subgroups.

Conclusions

SAP subgroups showed a good correlation of structural and functional defects when assessed using OCT and GDx VCC. These correlations were weaker in the Matrix subgroups, especially in the early stages of glaucoma.     

Long-term variability of GDx VCC retinal nerve fiber layer thickness measurements

PURPOSE: To evaluate the long-term variability of GDx VCC retinal nerve fiber layer (RNFL) thickness measurements. METHODS: The study enrolled a cohort of glaucoma suspects who did not develop any evidence of visual field damage or change in the appearance of the optic nerve during an average follow-up of 9.1+/-3.2 years. Subjects underwent ocular imaging using the commercially available GDx VCC scanning laser polarimeter. At each visit, each eye was imaged 3 times. Subjects underwent repeated testing with GDx VCC at approximately 12-month intervals during their follow-up. In total, 255 examinations were obtained in 31 eyes of 31 individuals during an average GDx VCC follow-up time of 26.0+/-8.9 months. A random effects analysis of variance model was used to estimate intraclass correlation coefficients and long-term and short-term variability estimates. RESULTS: Intraclass correlation coefficients ranged from 0.77 to 0.86 for GDx VCC parameters. Short-term variability estimates ranged from 2.45 to 3.89 microm for RNFL thickness parameters, whereas the short-term variability estimate for the parameter Nerve Fiber Indicator was 3.71. Long-term variability was slightly higher than short-term variability for all parameters. For RNFL thickness parameters, long-term variability estimates ranged from 3.21 to 4.97 microm, whereas for the parameter Nerve Fiber Indicator the long-term variability estimate was 4.93. CONCLUSIONS: RNFL measurements obtained with the GDx VCC were found to be highly reproducible in a long-term test-retest situation, supporting the use of this instrument for longitudinal assessment of the RNFL.     

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.     

Polarimetric measurement of retinal nerve fiber layer thickness in glaucoma diagnosis

PURPOSE: To evaluate reliability and diagnostic value of polarimetric measurements of the retinal nerve fiber layer (RNFL) thickness in the diagnosis of glaucoma. METHODS: The study included 81 eyes with perimetric glaucoma with glaucomatous changes of the optic disc and visual field defects; 52 eyes with preperimetric glaucoma with glaucomatous optic disc abnormalities and normal achromatic visual fields; and 70 normal eyes. For determination of reliability, four examiners repeated polarimetric measurements five times in ten normal subjects. RESULTS: The polarimetric variables were significantly correlated with increasing mean visual field defect and decreasing neuroretinal rim area. In correlation analyses with visual field defects, correlation coefficients were highest for the variable "superior/nasal ratio" and "the Number," a variable calculated by the neural network of the device. In correlations with neuroretinal rim area, correlation coefficients were highest for measurements of the inferior nerve fiber layer thickness. The preperimetric glaucoma group and the control group differed significantly in the variables "superior/nasal ratio" and "the Number" and, to a smaller degree, in the variables "superior/temporal ratio" and "superior/inferior ratio." The Number variable had a sensitivity of 82% and 58% at a predefined specificity of 80% in separating perimetric glaucoma patients and preperimetric glaucoma patients, respectively, from control subjects. Reproducibility of the polarimetric measurements ranged between 70% and 89%. CONCLUSION: Polarimetric measurements of the RNFL thickness can detect glaucomatous optic nerve damage in patients with visual field loss, and in some patients with preperimetric glaucomatous optic nerve damage. Considering the fast performance, easy handling, and low maintenance costs, RNFL polarimetry may be helpful in glaucoma diagnosis.