Comparison between GDx VCC scanning laser polarimetry and Stratus OCT optical coherence tomography in the diagnosis of chronic glaucoma

Microperimetry, Humphrey field analyzer, and optical coherence tomography in detecting glaucoma: a comparative performance study

PURPOSE

To evaluate and compare the diagnostic performance of microperimetry (MP), visual field (VF) 10-2 and 24-2 tests, and spectral-domain optical coherence tomography (SD-OCT) in primary open-angle glaucoma (POAG).

METHODS

The study consisted of 35 POAG and 42 control eyes were enrolled in this prospective study. Eligible participants were ≥ 50 years old. VF assessments were carried out using the Humphrey field analyzer (HFA) and Macular Integrity Assessment. Optic nerve head (ONH), retinal nerve fiber layer thickness (RNFLT), and ganglion cell inner-plexiform-layer thickness (GCIPLT) were measured by SD-OCT. Areas under the receiver operating characteristic curves (AUC) and sensitivities at 95% specificity were calculated for each parameter.

RESULTS

HFA 24-2 had the largest AUC value among the functional parameters to differentiate POAG from control eyes [AUC: 0.950 (0.906-0.994), sensitivity at 95%:60]. HFA 24-2 showed a significantly better performance than the 10-2 test (p = 0.036). Among the SD-OCT structural parameters, minimum GCIPLT had the largest AUC value to differentiate POAG from control eyes [AUC: 0.952 (0.905-0.999), sensitivity at 95%:80]. In comparison of the functional and structural parameters, HFA 24-2 showed a significantly better performance than the 10-2 test (p = 0.036). In macular parameters, minimum GCPLT performed significantly better than HFA 10-2 (p = 0.015) in detecting POAG. There was no statistically significant difference between the comparative diagnostic performance of the RNFL, ONH, HFA, and MP (p > 0.05 for all comparisons).

CONCLUSION

The structural and functional test results revealed that GCIPLT measurements had the highest diagnostic performance in detecting POAG. HFA 24-2 test performed better than 10-2 test in distinguishing glaucoma from healthy eyes. MP showed a similar performance with HFA 10-2 and may be considered a complementary diagnostic tool.

Retinal nerve fibre layer thickness measurements in childhood glaucoma: the role of scanning laser polarimetry and optical coherence tomography

Purpose

A central diagnostic tool in adult glaucoma is the peripapillary retinal nerve fibre layer (pRNFL) thickness. It can be assessed by scanning laser polarimetry (SLP) or optical coherence tomography (OCT). However, studies investigating the relevance of pRNFL measurements in children are rare. This study aims to compare the glaucoma diagnosing ability of SLP and OCT pRNFL thickness measurements in a paediatric population.

Methods

This retrospective study included 105 children (glaucoma: 22 (21.0%); healthy glaucoma suspects: 83 (79.0%)) aged 4–18 years, examined with SLP (GDxPro/ECC, Carl Zeiss Meditec) and spectral-domain OCT (SPECTRALIS®, Heidelberg Engineering). The thickness of pRNFL sectors was compared between diseased and healthy participants. Areas under the receiver-operating characteristic curves (AUC) and logistic regression results were used to compare the glaucoma discriminative capacity between SLP and OCT measurements.

Results

Using OCT, pRNFL thickness was decreased in the superior, nasal, and inferior quadrants of glaucoma patients compared to healthy controls (P < 0.001, each). With SLP, such a difference was only observed in the inferior quadrant (P = 0.011). A correlation between glaucoma diagnosis and OCT-measured pRNFL thickness was found in all quadrants (P < 0.001) other than the temporal. With SLP, a correlation was found for the total average thickness (P = 0.037) and inferior quadrant (P = 0.0019). Finally, the AUCs of OCT measurements were markedly higher than those of SLP (e.g., inferior quadrant: OCT 0.83, SLP 0.68).

Conclusion

pRNFL thickness measurements using both OCT and SLP, correlate notably with the presence of glaucoma. In general, the diagnostic performance of pRNFL thickness measurements seems higher for OCT than for SLP. Thus, pRNFL thickness measurements could provide important information, complementing conventional clinical and functional parameters in the diagnostic process of paediatric glaucoma.

Predictive Factors for Visual Field Conversion: Comparison of Scanning Laser Polarimetry and Optical Coherence Tomography

PURPOSE

The purpose of this study was to compare the ability of scanning laser polarimetry (SLP) and spectral-domain optical coherence tomography (SD-OCT) to predict future visual field conversion of subjects with ocular hypertension and early glaucoma.

METHODS

All patients were recruited from the Erlangen glaucoma registry and examined using standard automated perimetry, 24-hour intraocular pressure profile, and optic disc photography. Peripapillary retinal nerve fiber layer thickness (RNFL) measurements were obtained by SLP (GDx-VCC) and SD-OCT (Spectralis OCT). Positive and negative predictive values (PPV, NPV) were calculated for morphologic parameters of SLP and SD-OCT. Kaplan-Meier survival curves were plotted and log-rank tests were performed to compare the survival distributions. Contingency tables and Venn-diagrams were calculated to compare the predictive ability.

RESULTS

The study included 207 patients-75 with ocular hypertension, 85 with early glaucoma, and 47 controls. Median follow-up was 4.5 years. A total of 29 patients (14.0%) developed visual field conversion during follow-up. SLP temporal-inferior RNFL [0.667; 95% confidence interval (CI), 0.281-0.935] and SD-OCT temporal-inferior RNFL (0.571; 95% CI, 0.317-0.802) achieved the highest PPV; nerve fiber indicator (0.923; 95% CI, 0.876-0.957) and SD-OCT mean (0.898; 95% CI, 0.847-0.937) achieved the highest NPV of all investigated parameters. The Kaplan-Meier curves confirmed significantly higher survival for subjects within normal limits of measurements of both devices (P<0.001). Venn diagrams tested with McNemar test statistics showed no significant difference for PPV (P=0.219) or NPV (P=0.678).

CONCLUSIONS

Both GDx-VCC and SD-OCT demonstrate comparable results in predicting future visual field conversion if taking typical scans for GDx-VCC. In addition, the likelihood ratios suggest that GDx-VCC's nerve fiber indicator<30 may be the most useful parameter to confirm future nonconversion. (http://www.ClinicalTrials.gov number, NTC00494923; Erlangen Glaucoma Registry).

Optical coherence tomography for glaucoma diagnosis: An evidence based meta-analysis

Purpose

Early detection, monitoring and understanding of changes in the retina are central to the diagnosis of glaucomatous optic neuropathy, and vital to reduce visual loss from this progressive condition. The main objective of this investigation was to compare glaucoma diagnostic accuracy of commercially available optical coherence tomography (OCT) devices (Zeiss Stratus, Zeiss Cirrus, Heidelberg Spectralis and Optovue RTVue, and Topcon 3D-OCT).

Patients

16,104 glaucomatous and 11,543 normal eyes reported in 150 studies.

Methods

Between Jan. 2017 and Feb 2017, MEDLINE^®, EMBASE^®, CINAHL^®, Cochrane Library^®, Web of Science^®, and BIOSIS^® were searched for studies assessing glaucoma diagnostic accuracy of the aforementioned OCT devices. Meta-analysis was performed pooling area under the receiver operating characteristic curve (AUROC) estimates for all devices, stratified by OCT type (RNFL, macula), and area imaged.

Results

150 studies with 16,104 glaucomatous and 11,543 normal control eyes were included. Key findings: AUROC of glaucoma diagnosis for RNFL average for all glaucoma patients was 0.897 (0.887–0.906, n = 16,782 patient eyes), for macula ganglion cell complex (GCC) was 0.885 (0.869–0.901, n = 4841 eyes), for macula ganglion cell inner plexiform layer (GCIPL) was 0.858 (0.835–0.880, n = 4211 eyes), and for total macular thickness was 0.795 (0.754–0.834, n = 1063 eyes).

Conclusion

The classification capability was similar across all 5 OCT devices. More diagnostically favorable AUROCs were demonstrated in patients with increased glaucoma severity. Diagnostic accuracy of RNFL and segmented macular regions (GCIPL, GCC) scans were similar and higher than total macular thickness. This study provides a synthesis of contemporary evidence with features of robust inclusion criteria and large sample size. These findings may provide guidance to clinicians when navigating this rapidly evolving diagnostic area characterized by numerous options.

Comparison of Laser Scanning Diagnostic Devices for Early Glaucoma Detection

BACKGROUND

To compare the diagnostic accuracy and to evaluate the correlation of optic nerve head and retinal nerve fiber layer thickness values between Fourier-Domain optical coherence tomography (FD-OCT), confocal scanning laser ophthalmoscopy (CSLO), and scanning laser polarimetry (SLP) for early glaucoma detection.

PATIENTS AND METHODS

Ninety-three patients with early open-angle glaucoma, 58 patients with ocular hypertension, and 60 healthy control subjects were included in this observational, cross-sectional study. All study participants underwent FD-OCT (RTVue-100), CSLO (HRT3), and SLP (GDx VCC) imaging of the optic nerve head and the retinal nerve fiber layer. Area under the receiver operating characteristic curves (AUROC) and Bland-Altman analysis were performed.

RESULTS

The parameters with the highest diagnostic accuracy were found for FD-OCT cup-to-disc ratio (AUROC=0.841), for SLP NFI (AUROC=0.835), and for CSLO cup-to-disc ratio (AUROC=0.789). Diagnostic accuracy of the best CSLO and SLP parameter was similar (P=0.259). There was a small statistically significant difference between the best CSLO and FD-OCT parameters for differentiating between glaucoma and healthy eyes (P=0.047).

CONCLUSIONS

FD-OCT and SLP have a similarly good diagnostic ability to distinguish between early glaucoma and healthy subjects. The diagnostic accuracy of CSLO was comparable with SLP and marginally lower compared with FD-OCT.

Optic nerve head and fibre layer imaging for diagnosing glaucoma

BACKGROUND

The diagnosis of glaucoma is traditionally based on the finding of optic nerve head (ONH) damage assessed subjectively by ophthalmoscopy or photography or by corresponding damage to the visual field assessed by automated perimetry, or both. Diagnostic assessments are usually required when ophthalmologists or primary eye care professionals find elevated intraocular pressure (IOP) or a suspect appearance of the ONH. Imaging tests such as confocal scanning laser ophthalmoscopy (HRT), optical coherence tomography (OCT) and scanning laser polarimetry (SLP, as used by the GDx instrument), provide an objective measure of the structural changes of retinal nerve fibre layer (RNFL) thickness and ONH parameters occurring in glaucoma.

OBJECTIVES

To determine the diagnostic accuracy of HRT, OCT and GDx for diagnosing manifest glaucoma by detecting ONH and RNFL damage.

SEARCH METHODS

We searched several databases for this review. The most recent searches were on 19 February 2015.

SELECTION CRITERIA

We included prospective and retrospective cohort studies and case-control studies that evaluated the accuracy of OCT, HRT or the GDx for diagnosing glaucoma. We excluded population-based screening studies, since we planned to consider studies on self-referred people or participants in whom a risk factor for glaucoma had already been identified in primary care, such as elevated IOP or a family history of glaucoma. We only considered recent commercial versions of the tests: spectral domain OCT, HRT III and GDx VCC or ECC.

DATA COLLECTION AND ANALYSIS

We adopted standard Cochrane methods. We fitted a hierarchical summary ROC (HSROC) model using the METADAS macro in SAS software. After studies were selected, we decided to use 2 x 2 data at 0.95 specificity or closer in meta-analyses, since this was the most commonly-reported level.

MAIN RESULTS

We included 106 studies in this review, which analysed 16,260 eyes (8353 cases, 7907 controls) in total. Forty studies (5574 participants) assessed GDx, 18 studies (3550 participants) HRT, and 63 (9390 participants) OCT, with 12 of these studies comparing two or three tests. Regarding study quality, a case-control design in 103 studies raised concerns as it can overestimate accuracy and reduce the applicability of the results to daily practice. Twenty-four studies were sponsored by the manufacturer, and in 15 the potential conflict of interest was unclear.Comparisons made within each test were more reliable than those between tests, as they were mostly based on direct comparisons within each study.The Nerve Fibre Indicator yielded the highest accuracy (estimate, 95% confidence interval (CI)) among GDx parameters (sensitivity: 0.67, 0.55 to 0.77; specificity: 0.94, 0.92 to 0.95). For HRT measures, the Vertical Cup/Disc (C/D) ratio (sensitivity: 0.72, 0.60 to 0.68; specificity: 0.94, 0.92 to 0.95) was no different from other parameters. With OCT, the accuracy of average RNFL retinal thickness was similar to the inferior sector (0.72, 0.65 to 0.77; specificity: 0.93, 0.92 to 0.95) and, in different studies, to the vertical C/D ratio.Comparing the parameters with the highest diagnostic odds ratio (DOR) for each device in a single HSROC model, the performance of GDx, HRT and OCT was remarkably similar. At a sensitivity of 0.70 and a high specificity close to 0.95 as in most of these studies, in 1000 people referred by primary eye care, of whom 200 have manifest glaucoma, such as in those who have already undergone some functional or anatomic testing by optometrists, the best measures of GDx, HRT and OCT would miss about 60 cases out of the 200 patients with glaucoma, and would incorrectly refer 50 out of 800 patients without glaucoma. If prevalence were 5%, e.g. such as in people referred only because of family history of glaucoma, the corresponding figures would be 15 patients missed out of 50 with manifest glaucoma, avoiding referral of about 890 out of 950 non-glaucomatous people.Heterogeneity investigations found that sensitivity estimate was higher for studies with more severe glaucoma, expressed as worse average mean deviation (MD): 0.79 (0.74 to 0.83) for MD < -6 db versus 0.64 (0.60 to 0.69) for MD ≥ -6 db, at a similar summary specificity (0.93, 95% CI 0.92 to 0.94 and, respectively, 0.94; 95% CI 0.93 to 0.95; P < 0.0001 for the difference in relative DOR).

AUTHORS' CONCLUSIONS

The accuracy of imaging tests for detecting manifest glaucoma was variable across studies, but overall similar for different devices. Accuracy may have been overestimated due to the case-control design, which is a serious limitation of the current evidence base.We recommend that further diagnostic accuracy studies are carried out on patients selected consecutively at a defined step of the clinical pathway, providing a description of risk factors leading to referral and bearing in mind the consequences of false positives and false negatives in the setting in which the diagnostic question is made. Future research should report accuracy for each threshold of these continuous measures, or publish raw data.

An examination of the hypothesis that intraocular pressure elevation episodes can have prognostic significance in glaucoma suspects

The efficacy of intraocular pressure reduction in retarding the progression of glaucoma has been demonstrated. This review examines the potential for prognostic advantage for glaucoma suspects in reducing their optic nerve head exposure to elevated intraocular pressure associated with activities which have been shown to elevate intraocular pressure. In this observational study, patients examined at the Centre for Eye Health (University of New South Wales) with a diagnosis of glaucoma suspect were surveyed to determine their histories for participation in activities which are known to elevate intraocular pressure. The evidence regarding the pathological significance of these sources of elevation in susceptible patients was examined. Apart from the universality of sleep-related intraocular pressure elevations, the histories from 183 confirmed glaucoma suspects indicate a wide range and variation in frequency of participation in other intraocular pressure elevating activities. A reduction in exposure to elevated intraocular pressure may improve the prognosis for glaucoma suspects. Additional patient specific assessment of the results of this screening could provide an indication of the degree (frequency, intensity level and duration) of exposure to elevated intraocular pressure. Such information may provide the basis for improving a patient's prognosis by helping them to identify opportunities to reduce such exposure to elevated intraocular pressure. Any benefit of reduction of such exposure appears likely to be greater if activities which elevate intraocular pressure are of long duration, occur frequently, occur over a long period of time, and/or involve high levels of intraocular pressure elevation.

Diagnostic capability of spectral-domain optical coherence tomography for glaucoma

PURPOSE

To determine the diagnostic capability of spectral-domain optical coherence tomography in glaucoma patients with visual field defects.

DESIGN

Prospective, cross-sectional study.

METHODS

SETTINGS

Participants were recruited from a university hospital clinic.

STUDY POPULATION

One eye of 85 normal subjects and 61 glaucoma patients with average visual field mean deviation of -9.61 ± 8.76 dB was selected randomly for the study. A subgroup of the glaucoma patients with early visual field defects was calculated separately.

OBSERVATION PROCEDURES

Spectralis optical coherence tomography (Heidelberg Engineering, Inc) circular scans were performed to obtain peripapillary retinal nerve fiber layer (RNFL) thicknesses. The RNFL diagnostic parameters based on the normative database were used alone or in combination for identifying glaucomatous RNFL thinning.

MAIN OUTCOME MEASURES

To evaluate diagnostic performance, calculations included areas under the receiver operating characteristic curve, sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio.

RESULTS

Overall RNFL thickness had the highest area under the receiver operating characteristic curve values: 0.952 for all patients and 0.895 for the early glaucoma subgroup. For all patients, the highest sensitivity (98.4%; 95% confidence interval, 96.3% to 100%) was achieved by using 2 criteria: ≥ 1 RNFL sectors being abnormal at the < 5% level and overall classification of borderline or outside normal limits, with specificities of 88.9% (95% confidence interval, 84.0% to 94.0%) and 87.1% (95% confidence interval, 81.6% to 92.5%), respectively, for these 2 criteria.

CONCLUSIONS

Statistical parameters for evaluating the diagnostic performance of the Spectralis spectral-domain optical coherence tomography were good for early perimetric glaucoma and were excellent for moderately advanced perimetric glaucoma.

Influence of optic disc size on the diagnostic performance of macular ganglion cell complex and peripapillary retinal nerve fiber layer analyses in glaucoma

Aim

To evaluate the influence of optic disc size on the diagnostic accuracy of macular ganglion cell complex (GCC) and conventional peripapillary retinal nerve fiber layer (pRNFL) analyses provided by spectral domain optical coherence tomography (SD-OCT) in glaucoma.

Methods

Eighty-two glaucoma patients and 30 healthy subjects were included. All patients underwent GCC (7 × 7 mm macular grid, consisting of RNFL, ganglion cell and inner plexiform layers) and pRNFL thickness measurement (3.45 mm circular scan) by SD-OCT. One eye was randomly selected for analysis. Initially, receiver operating characteristic (ROC) curves were generated for different GCC and pRNFL parameters. The effect of disc area on the diagnostic accuracy of these parameters was evaluated using a logistic ROC regression model. Subsequently, 1.5, 2.0, and 2.5 mm² disc sizes were arbitrarily chosen (based on data distribution) and the predicted areas under the ROC curves (AUCs) and sensitivities were compared at fixed specificities for each.

Results

Average mean deviation index for glaucomatous eyes was −5.3 ± 5.2 dB. Similar AUCs were found for the best pRNFL (average thickness = 0.872) and GCC parameters (average thickness = 0.824; P = 0.19). The coefficient representing disc area in the ROC regression model was not statistically significant for average pRNFL thickness (−0.176) or average GCC thickness (0.088; P ≥ 0.56). AUCs for fixed disc areas (1.5, 2.0, and 2.5 mm²) were 0.904, 0.891, and 0.875 for average pRNFL thickness and 0.834, 0.842, and 0.851 for average GCC thickness, respectively. The highest sensitivities – at 80% specificity for average pRNFL (84.5%) and GCC thicknesses (74.5%) – were found with disc sizes fixed at 1.5 mm² and 2.5 mm².

Conclusion

Diagnostic accuracy was similar between pRNFL and GCC thickness parameters. Although not statistically significant, there was a trend for a better diagnostic accuracy of pRNFL thickness measurement in cases of smaller discs. For GCC analysis, an inverse effect was observed.

Shape analysis of the peripapillary RPE layer in papilledema and ischemic optic neuropathy

PURPOSE

Geometric morphometrics (GM) was used to analyze the shape of the peripapillary retinal pigment epithelium-Bruch's membrane (RPE/BM) layer imaged on the SD-OCT 5-line raster in normal subjects and in patients with papilledema and ischemic optic neuropathy.

METHODS

Three groups of subjects were compared: 30 normals, 20 with anterior ischemic optic neuropathy (AION), and 25 with papilledema and intracranial hypertension. Twenty equidistant semilandmarks were digitized on OCT images of the RPE/BM layer spanning 2500 μm on each side of the neural canal opening (NCO). The data were analyzed using standard GM techniques, including a generalized least-squares Procrustes superimposition, principal component analysis, thin-plate spline (to visualize deformations), and permutation statistical analysis to evaluate differences in shape variables.

RESULTS

The RPE/BM layer in normals and AION have a characteristic V shape pointing away from the vitreous; the RPE/BM layer in papilledema has an inverted U shape, skewed nasally inward toward the vitreous. The differences were statistically significant. There was no significant difference in shapes between normals and AION. Pre- and posttreatment OCTs, in select cases of papilledema, showed that the inverted U-shaped RPE/BM moved posteriorly into a normal V shape as the papilledema resolved with weight loss or shunting.

CONCLUSIONS

The shape difference in papilledema, absent in AION, cannot be explained by disc edema alone. The difference is a consequence of both the translaminar pressure gradient and the material properties of the peripapillary sclera. GM offers a novel way of statistically assessing shape differences of the peripapillary optic nerve head.

Comparison of retinal nerve fibre layer thickness with visual evoked potential and visual field in patients with multiple sclerosis

BACKGROUND

To evaluate retinal nerve fibre layer thickness and to compare results with visual evoked potentials and visual field in patients with multiple sclerosis.

DESIGN

A prospective, case-control study, university hospital setting.

PARTICIPANTS

Seventy-three eyes of 37 multiple sclerosis patients and 74 eyes of 37 healthy subjects.

METHODS

All patients underwent a complete neurological and ophthalmological examination and peri-papillary retinal nerve fibre layer thickness was evaluated using scanning laser polarimetry (GDx). Furthermore, visual evoked potential and visual field testing were performed.

MAIN OUTCOME MEASURES

The χ(2) test, Student's t-test, Mann-Whitney U-test and Pearson's correlation coefficient analysis of the GDx, visual evoked potential and visual field testing parameters.

RESULTS

GDx measurements showed significantly more retinal nerve fibre layer damage in the patients than in the control groups. Comparison of the GDx parameters between patients with optic neuritis and non-optic neuritis demonstrated a statistically significant difference in symmetry (P = 0.046) and superior/nasal parameters (P = 0.009). A correlation was found between the number, superior and inferior ratio parameters, and P100 amplitude obtained with visual evoked potential in patients with non-optic neuritis. Additionally, there was a correlation between the number, inferior ratio and superior/nasal parameters, and the mean deviation of visual field in the non-optic neuritis group.

CONCLUSIONS

For retinal nerve fibre layer thickness measurements in multiple sclerosis patients, the GDx, along with other techniques, such as visual evoked potential, can be used as a diagnostic and follow-up criterion, particularly in patients without optic neuritis.

Influence of disc size on optic nerve head versus retinal nerve fiber layer assessment for diagnosing glaucoma

PURPOSE

To explore and compare the influence of optic disc size on the diagnostic accuracy of retinal nerve fiber layer (RNFL) thickness and optic nerve head (ONH) quantitative assessment.

DESIGN

Observational, cross-sectional evaluation of diagnostic tests.

PARTICIPANTS

We included 120 eyes from 50 normal subjects and 70 glaucomatous patients classified by the presence of a repeatable visual field defect for the analysis.

TESTING

The RNFL thickness was measured by scanning laser polarimetry with variable corneal compensator (GDx-VCC, Carl-Zeiss Meditec, Dublin, CA) and spectral-domain optical coherence tomography (Cirrus HD-OCT, Carl Zeiss Meditec, Inc). We obtained ONH imaging by means of confocal scanning laser ophthalmoscopy (HRT3; Heidelberg Engineering, GmbH, Dossenheim, Germany).

MAIN OUTCOME MEASURES

Sensitivity and specificity for normative classifications, sensitivity at fixed specificity and area under the receiver operating characteristics curve (AUC) for continuous parameters. A logistic marginal regression model and coefficients of variation (CoV) have been used to test and quantify the influence of optic disc size on the diagnostic accuracy of the 3 technologies under investigation.

RESULTS

Among continuous parameters average RNFL thickness for Cirrus HD-OCT, nerve fiber indicator for GDx-VCC and cup shape measure for the HRT3 showed the best diagnostic accuracy with an AUC of 0.97, 0.94, and 0.94, respectively. Among normative classifications, the highest sensitivity and specificity were found for OCT average RNFL thickness (75.8% and 94.7%), for GDx superior thickness (77.1% and 97.5%), for HRT3 Moorfields regression analysis result (89.4% and 73.7%) and for HRT3 GPS global (92.3% and 76.5%). The diagnostic performance of HRT3 parameters seemed to be significantly influenced by optic disc size, although the same was not true for Cirrus HD-OCT and GDx VCC. The most steady performers for each imaging device across disc size groups were Cirrus HD-OCT average thickness (CoV, 1.6%), GDx-VCC inferior thickness (CoV, 2.5%), and HRT3 GPS temporal and nasal (CoV, 21.4%).

CONCLUSIONS

The diagnostic accuracy of quantitative RNFL assessment as performed by Cirrus HD-OCT and GDx-VCC is high and virtually unaffected or only minimally affected by the size of the optic disc and may provide more consistent diagnostic outcomes across small and large discs than ONH assessment as performed by HRT3.

Relationship between GDx VCC and Stratus OCT in juvenile glaucoma

PURPOSE

To compare the ability of scanning laser polarimetry (GDx VCC) and optical coherence tomography (OCT) to discriminate eyes with juvenile glaucoma from normal eyes and to assess the relationship between their parameters.

METHODS

A total of 24 glaucomatous eyes of 24 patients and 24 normal eyes were enrolled. The age range of the patient was 11-40 years with a mean age of 25.1+/-8.2 years. Control groups consisted 24 eyes of 24 individuals without glaucoma with a mean age of 33.2+/-8.2 years. All subjects underwent a full ophthalmic examination, automated perimetry, GDx VCC, and OCT. Correlation coefficients between the parameters of OCT and GDx VCC were calculated. We calculated the area under the receiver operating characteristic curve (AROC) for the main parameters of GDx VCC and OCT.

RESULTS

Statistically significant correlations were observed between GDx VCC and OCT parameters. Pearson coefficients ranged from 0.75 for inferior average to 0.86 for nerve fibre indicator (NFI)/average thickness OCT. The greatest AROC parameter in OCT (inferior average: 0.92) had a lower area than that in GDx VCC (NFI: 0.99). There was a significant statistical significance in all visual field, GDx VCC, and OCT variables between two groups (P<0.05).

CONCLUSIONS

Many GDx VCC parameters were significantly correlated with those of the OCT in patients with juvenile glaucoma. Inferior average and NFI had the greatest AROC parameter in OCT and GDx VCC, respectively. NFI had high sensitivity and specificity for the diagnosis of JOAG.

Spectral-domain optical coherence tomography and scanning laser polarimetry in glaucoma diagnosis

PURPOSE

To evaluate glaucoma diagnostic capability of the retinal nerve fiber layer (RNFL) imaging by spectral-domain optical coherence tomography (Cirrus OCT) and scanning laser polarimetry (GDx VCC).

METHODS

We imaged 88 glaucomatous and 77 healthy eyes using both devices. Areas under the receiver-operating characteristic curves (area under the curves, AUCs) and sensitivities at fixed specificities of average, superior, and inferior RNFL thickness were compared. Likelihood ratios (LRs) and diagnostic agreement based on normative classifications yielded by both devices were determined.

RESULTS

The best performing parameter was the nerve fiber indicator (NFI) in GDx VCC and inferior RNFL thickness in Cirrus OCT (AUC = 0.912, 0.961, P = 0.045). The AUCs of the Cirrus OCT were significantly higher than those of GDx VCC in all parameters. Most of the parameters in Cirrus OCT were more sensitive than GDx VCC in the detection of glaucoma at fixed specificity values. Cirrus OCT had an infinite LR with abnormal classification results in both average and superior RNFL thickness. There was good agreement between the two instruments with respect to abnormal classifications (kappa, 0.611-0.766)

CONCLUSION

Both Cirrus OCT and GDx VCC RNFL measurements showed good glaucoma diagnostic capabilities. Cirrus OCT showed higher sensitivities than GDx VCC.

Effect of cataract surgery on retinal nerve fiber layer thickness parameters using scanning laser polarimetry (GDxVCC)

Purpose:

To study the effect of cataract extraction on the retinal nerve fiber layer (RNFL) thickness, and assessment by scanning laser polarimetry (SLP), with variable corneal compensation (GDx VCC), at the glaucoma service of a tertiary care center in North India.

Materials and Methods:

Thirty-two eyes of 32 subjects were enrolled in the study. The subjects underwent RNFL analysis by SLP (GDx VCC) before undergoing phacoemulsification cataract extraction with intraocular lens (IOL) implantation (Acrysof SA 60 AT) four weeks following cataract surgery. The RNFL thickness parameters evaluated both before and after surgery included temporal, superior, nasal, inferior, temporal (TSNIT) average, superior average, inferior average, and nerve fiber index (NFI).

Results:

The mean age of subjects was 57.6 ± 11.7 years (18 males, 14 females). Mean TSNIT average thickness (μm) pre- and post-cataract surgery was 49.2 ± 14.1 and 56.5 ± 7.6 (P = 0.001). There was a statistically significant increase in RNFL thickness parameters (TSNIT average, superior average, and inferior average) and decrease in NFI post-cataract surgery as compared to the baseline values. Mean NFI pre- and post-cataract surgery was 41.3 ± 15.3 and 21.6 ± 11.8 (P = 0.001).

Conclusions:

Measurement of RNFL thickness parameters by scanning laser polarimetry is significantly altered following cataract surgery. Post the cataract surgery, a new baseline needs to be established for assessing the longitudinal follow-up of a glaucoma patient. The presence of cataract may lead to an underestimation of the RNFL thickness, and this should be taken into account when analyzing progression in a glaucoma patient.

Diagnostic Capability of Scanning Laser Polarimetry with and without Enhanced Corneal Compensation and Optical Coherence Tomography

Purpose

TO compare the abilities of the current commercially available versions of scanning laser polarimetry (SLP) and optical coherence tomography (OCT), SLP-variable corneal compensation (VCC), SLP–enhanced corneal compensation (ECC), and high-definition (HD) OCT, in discriminating between healthy eyes and those with early-to-moderate glaucomatous visual field loss.

Methods

Healthy volunteers and patients with glaucoma who met the eligibility criteria were consecutively enrolled in this prospective, cross-sectional, observational study. Subjects underwent complete eye examination, automated perimetry, SLP-ECC, SLP-VCC, and HD-OCT Scanning laser polarimetry parameters were recalculated in 90-degree segments (quadrants) in the calculation circle to be compared. Areas under the receiver operating characteristic curve (AUROCs) were calculated for every parameter in order to compare the ability of each imaging modality to differentiate between normal and glaucomatous eyes.

Results

Fifty-five normal volunteers (mean age 59.1 years) and 33 patients with glaucoma (mean age 63.8 years) were enrolled. Average visual field mean deviation was −6.69 dB (95% confidence interval −8.07 to −5.31) in the glaucoma group. The largest AUROCs were associated with nerve fiber indicator (0.880 and 0.888) for the SLP-VCC and SLP-ECC, respectively, and with the average thickness in the HD-OCT (0.897).

Conclusions

The best performing indices for the SLP-VCC, SLP-ECC, and HD OCT gave similar AUROCs, showing moderate diagnostic accuracy in patients with early to moderate glaucoma. Further studies are needed to evaluate the ability of these technologies to discriminate between normal and glaucomatous eyes.

Comparison of optical coherence tomography and scanning laser polarimetry measurements in patients with multiple sclerosis

PURPOSE

To compare optical coherence tomography (OCT) and scanning laser polarimetry (GDx) measurements of the retinal nerve fiber layer (RNFL) in multiple sclerosis (MS) patients with and without optic neuritis (ON).

METHODS

OCT and GDx were performed on 68 MS patients. Qualifying eyes were divided into two groups: 51 eyes with an ON history > or =6 months before (ON eyes) and 65 eyes with no history of ON (non-ON eyes). Several GDx and OCT parameters and criteria were used to define an eye as abnormal, for example, GDx nerve fiber indicator (NFI) >20 or 30, OCT average RNFL thickness, and GDx temporal-superior-nasal-inferior-temporal average (TSNIT) below 5 or 1% of the normative database of the instruments. Agreement between OCT and GDx parameters was reported as percent of observed agreement, along with the AC1 statistic. Linear regression analyses were used to examine the relationship between OCT average RNFL thickness and GDx NFI and TSNIT.

RESULTS

All OCT and GDx measurements showed significantly more RNFL damage in ON than in non-ON eyes. Agreement between OCT and GDx parameters ranged from 69 to 90% (AC1 0.37 to 0.81) in ON eyes and 52 to 91% (AC1 = 0.21 to 0.90) in non-ON eyes. Best agreement was observed between OCT average RNFL thickness (p < 0.01) and NFI (>30) in ON eyes (90%, AC1 = 0.81) and between OCT average RNFL thickness (p < 0.01) and GDx TSNIT average (p < 0.01) in non-ON eyes (91%, AC1 = 0.90). In ON eyes, the OCT average RNFL thickness showed good linear correlation with NFI (R = 0.69, p < 0.0001) and TSNIT (R = 0.55, p < 0.0001).

CONCLUSIONS

OCT and GDx show good agreement and can be useful in detecting RNFL loss in MS/ON eyes.

Comparison of optical coherence tomography and scanning laser polarimetry for detection of localized retinal nerve fiber layer defects

PURPOSES

To compare the ability of Stratus optical coherence tomography (Stratus OCT) and scanning laser polarimetry with variable corneal compensator (GDx VCC) in recognizing a localized retinal nerve fiber layer (RNFL) defect identified on red-free fundus photography.

MATERIALS AND METHODS

Fifty-three patients with only 1 localized RNFL defect in either eye were taken RNFL thickness analysis using Stratus OCT and GDx VCC. Thirty-nine healthy subjects were used as controls and only 1 eye per subject was considered. Using red-free photography as the standard reference test, sensitivity and specificity for photographic defects, and topographic correlation with photographic defects were compared between Stratus OCT (sector average graph) and GDx VCC (deviation from normal map). Abnormal sectors at P<5% compared with their internal normative database were evaluated.

RESULTS

After excluding eyes with unacceptable scan images, 38 healthy eyes and 47 glaucomatous eyes were finally included. Stratus OCT and GDx VCC showed moderate sensitivity (78.7%) and high specificity (94.7% and 89.5%, respectively), and there was no significant difference (P=1.00 and P=0.69, respectively). RNFL defects determined by Stratus OCT and GDx VCC were correlated well with photographic RNFL defects in terms of peripapillary localization and clock-hour size, and there was no significant difference between 2 imaging devices (P=0.20 and P=0.27, respectively).

CONCLUSIONS

In recognizing a localized RNFL defect, overall diagnostic performance of Stratus OCT and GDx VCC with regard to their internal normative database was not significantly different. As both Stratus OCT and GDx VCC showed only moderate sensitivity, these imaging devices may not substitute red-free fundus photography in clinical practice of glaucoma diagnosis.

Comparison of scanning laser polarimetry and optical coherence tomography in quantitative retinal nerve fiber assessment

PURPOSE

To investigate the relationship between retinal nerve fiber layer (RNFL) measurements in corresponding areas obtained with scanning laser polarimetry and optical coherence tomography and to compare their discriminating ability in the diagnosis of preperimetric and perimetric glaucoma.

PATIENTS AND METHODS

Three hundred eighty-six subjects-57 healthy controls, 145 ocular hypertensive patients, 89 with preperimetric glaucoma, and 95 with perimetric glaucoma-were recruited from the Erlangen Glaucoma Registry. Perimetry, 24-hours intraocular pressure profile, stereographic optic disc slides, optical coherence tomography StratusOCT, and scanning laser polarimetry GDx VCC (Carl Zeiss Meditec, Inc, Dublin, CA) were performed in all patients. Receiver operating characteristic (ROC) curves were constructed for mean RNFL values, sector data, and indices. Sensitivity was estimated at >or=90% and >or=80% of specificity to compare the discriminating ability of each imaging modality.

RESULTS

For discrimination between glaucomatous and healthy eyes in GDx VCC the nerve fiber index demonstrated the largest area under the ROC curve (AUROC) (0.962+/-0.013), whereas in StratusOCT the largest AUROC (0.986+/-0.006) was found in the inferior quadrant. For preperimetric glaucoma detection the nerve fiber index achieved the largest AUROC (0.783+/-0.037). In contrast, the total RNFL average obtained using StratusOCT showed the largest AUROC (0.904+/-0.025). Bland-Altman plots showed good agreement between both instruments.

CONCLUSIONS

Both the GDx VCC and StratusOCT demonstrate increasing RNFL loss with advanced glaucomatous damage and were comparable in the diagnosis of perimetric glaucoma. Preperimetric glaucomatous damage may be better assessed by StratusOCT.

The location of the inferior and superior temporal blood vessels and interindividual variability of the retinal nerve fiber layer thickness

PURPOSE

To determine if adjusting for blood vessel (BV) location can decrease the intersubject variability of retinal nerve fiber layer (RNFL) thickness measured with optical coherence tomography (OCT).

SUBJECTS AND METHODS

One eye of 50 individuals with normal vision was tested with OCT and scanning laser polarimetry (SLP). The SLP and OCT RNFL thickness profiles were determined for a peripapillary circle 3.4 mm in diameter. The midpoints between the superior temporal vein and artery (STva) and the inferior temporal vein and artery (ITva) were determined at the location where the vessels cross the 3.4 mm circle. The average OCT and SLP RNFL thicknesses for quadrants and arcuate sectors of the lower and upper optic disc were obtained before and after adjusting for BV location. This adjustment was carried out by shifting the RNFL profiles based upon the locations of the STva and ITva relative to the mean locations of all 50 individuals.

RESULTS

Blood vessel locations ranged over 39 (STva) and 33 degrees (ITva) for the 50 eyes. The location of the leading edge of the OCT and SLP profiles was correlated with the location of the BVs for both the superior [r=0.72 (OCT) and 0.72 (SLP)] and inferior [r=0.34 and 0.43] temporal vessels. However, the variability in the OCT and SLP thickness measurements showed little change due to shifting. After shifting, the difference in the coefficient of variation ranged from -2.1% (shifted less variable) to +1.7% (unshifted less variable).

CONCLUSIONS

The shape of the OCT and SLP RNFL profiles varied systematically with the location of the superior and inferior superior veins and arteries. However, adjusting for the location of these major temporal BVs did not decrease the variability for measures of OCT or SLP RNFL thickness.

Screening for glaucoma in high-risk populations using optical coherence tomography

OBJECTIVE

To estimate the diagnostic accuracy of Stratus optical coherence tomography (OCT) for glaucoma screening in high-risk populations.

DESIGN

Cross-sectional evaluation of a diagnostic test for screening.

PARTICIPANTS

Three hundred thirty-three community-based volunteer participants with risk factors for glaucoma.

METHODS

The optic nerve and peripapillary retinal nerve fiber layer (RNFL) of participants' eyes were scanned using the Stratus OCT. Based on an ophthalmologic examination and frequency doubling perimetry, eyes were classified into 4 categories: normal, possible glaucoma, probable glaucoma, and definitive glaucoma.

MAIN OUTCOME MEASURES

The sensitivities, specificities, positive and negative likelihood ratios of the RNFL, optic disc parameters, and their combinations were calculated.

RESULTS

The right eyes were retained for analyses. After excluding eyes with missing data or with poor quality scans, the data of 210 right eyes were analyzed. Six eyes had definitive glaucoma. Combining the best performing optic nerve head parameters (cup diameter or cup/disc vertical ratio or cup/disc area ratio) and RNFL parameters (superior average or inferior average or overall average) using AND-logic resulted in a sensitivity of 67% (95% confidence interval [CI], 24%-94%), specificity of 96% (95% CI, 92%-98%), a positive likelihood ratio of 17.08 (95% CI, 7.06-41.4), and a negative likelihood ratio of 0.35 (95% CI, 0.11-1.08).

CONCLUSIONS

When adequate quality scans may be obtained, the Stratus has moderate sensitivity and high specificity for definitive glaucoma. Specificity is increased when parameters from both the optic nerve head and RNFL scans are combined.

Scanning laser polarimetry and optical coherence tomography for detection of retinal nerve fiber layer defects

PURPOSE

To compare the ability of scanning laser polarimetry with variable corneal compensation (GDx-VCC) and Stratus optical coherence tomography (OCT) to detect photographic retinal nerve fiber layer (RNFL) defects.

METHODS

This retrospective cross-sectional study included 45 eyes of 45 consecutive glaucoma patients with RNFL defects in red-free fundus photographs. The superior and inferior temporal quadrants in each eye were included for data analysis separately. The location and presence of RNFL defects seen in red-free fundus photographs were compared with those seen in GDx-VCC deviation maps and OCT RNFL analysis maps for each quadrant.

RESULTS

Of the 90 quadrants (45 eyes), 31 (34%) had no apparent RNFL defects, 29 (32%) had focal RNFL defects, and 30 (33%) had diffuse RNFL defects in red-free fundus photographs. The highest agreement between GDx-VCC and red-free photography was 73% when we defined GDx-VCC RNFL defects as a cluster of three or more color-coded squares (p<5%) along the traveling line of the retinal nerve fiber in the GDx-VCC deviation map (kappa value, 0.388; 95% confidence interval (CI), 0.195 to 0.582). The highest agreement between OCT and red-free photography was 85% (kappa value, 0.666; 95% CI, 0.506 to 0.825) when a value of 5% outside the normal limit for the OCT analysis map was used as a cut-off value for OCT RNFL defects.

CONCLUSIONS

According to the kappa values, the agreement between GDx-VCC deviation maps and red-free photography was poor, whereas the agreement between OCT analysis maps and red-free photography was good.

Effect of signal strength and improper alignment on the variability of stratus optical coherence tomography retinal nerve fiber layer thickness measurements

PURPOSE

To evaluate the effect of signal strength and improper scan alignment on retinal nerve fiber layer (RNFL) thickness measurement variability.

DESIGN

Retrospective, longitudinal clinical study.

METHODS

All eyes of healthy subjects with at least 2 fast RNFL scan sessions were selected from the Diagnostic Innovations in Glaucoma Study. The chronological first scan was considered to be the baseline. Absolute differences in signal strength and RNFL thickness measurements between baseline and subsequent scans were calculated. Regression analysis was conducted to assess whether signal strength and scan shifts along the horizontal (nasal-temporal) but not the vertical (superior-inferior) axis affect average RNFL thickness measurements.

RESULTS

Ninety-four eyes of 94 subjects were included. All eyes were tested twice or more on the same visit, whereas 30 eyes were followed up longitudinally for 32.4 +/- 13.3 months (1 scan per annual follow-up). For quadrants, absolute differences from baseline were greater than for average RNFL thickness and were significantly larger for scans acquired on separate visits. Average RNFL thickness increased only when the difference between the nasal and temporal quadrants increased (R2 = 0.16; P < .0001), suggesting it may be affected by horizontal but not vertical scan shifts. Differences in signal strength were associated with differences in average RNFL thickness (R2 = 0.19; P < .0001).

CONCLUSIONS

Even under optimal testing conditions, scan quality can adversely effect the ability to detect change over time. Therefore, caution is warranted when detecting glaucomatous progression using scan series of different quality. Careful overall assessment of quadrants and average RNFL thickness measurements is suggested to help identify scan misalignment.

Agreement between spectral-domain and time-domain OCT for measuring RNFL thickness

BACKGROUND/AIMS

To evaluate spectral-domain (SD) optical coherence tomography (OCT) reproducibility and assess the agreement between SD-OCT and Time-Domain (TD) OCT retinal nerve fibre layer (RNFL) measurements.

METHODS

Three Cirrus-SD-OCT scans and one Stratus-TD-OCT scan were obtained from Diagnostic Innovations in Glaucoma Study (DIGS) healthy participants and glaucoma patients on the same day. Repeatability was evaluated using Sw (within-subject standard deviation), CV (coefficient of variation) and ICC (intraclass correlation coefficient). Agreement was assessed using correlation and Bland-Altman plots.

RESULTS

16 healthy participants (32 eyes) and 39 patients (78 eyes) were included. SD-OCT reproducibility was excellent in both groups. The CV and ICC for Average RNFL thickness were 1.5% and 0.96, respectively, in healthy eyes and 1.6% and 0.98, respectively, in patient eyes. Correlations between RNFL parameters were strong, particularly for average RNFL thickness (R(2) = 0.92 in patient eyes). Bland-Altman plots showed good agreement between instruments, with better agreement for average RNFL thickness than for sectoral RNFL parameters (for example, at 90 microm average RNFL thickness, 95% limits of agreement were -13.1 to 0.9 for healthy eyes and -16.2 to -0.3 microm for patient eyes).

CONCLUSIONS

SD-OCT measurements were highly repeatable in healthy and patient eyes. Although the agreement between instruments was good, TD-OCT provided thicker RNFL measurements than SD-OCT. Measurements with these instruments should not be considered interchangeable.

Scan tracking coordinates for improved centering of Stratus OCT scan pattern

OBJECTIVE

To describe and evaluate a technique to optimize scan centering during the Stratus optical coherence tomography (OCT) image acquisition process using currently available scan tracking coordinates.

DESIGN

Observational clinical study.

PARTICIPANTS

Twelve eyes of six normal subjects were examined using the Fast retinal nerve fiber layer (RNFL) thickness and the Fast Optic Disc acquisition protocols.

METHODS

At visit 1, 3 consecutive measurements (trials) were taken by 2 different operators with the scan subjectively centered on the optic disc for the Fast RNFL thickness protocol and Fast Optic Disc protocol. At visit 2, 3 consecutive measurements were taken by positioning the scan using scan tracking coordinates. The scan coordinates were recorded twice by each operator and the limits of agreement and Bland-Altman plots were used to estimate agreement. The within subjects standard deviation (Sw) and the coefficient of variation (CV) were calculated for RNFL and optic disc parameters for each operator separately and differences by scan positioning method were evaluated using a 3-way (trial x operator x visit) analysis of variance for repeated measures.

RESULTS

The Sw and CV for the RNFL thickness parameters were generally higher when the scan was subjectively centered on the disc compared to when using the newly described coordinate system (eg, for operator 2, temporal sector Sw was 1.60+/-0.78 and 4.09+/-0.99 and CV was 2.2% and 5.7% with and without coordinate use, respectively). For the Fast RNFL protocol, the use of scan tracking coordinates resulted in significantly less variability than subjective placement of the scan circle using the landmark feature (currently recommended technique) in the temporal sectors only. No significant difference was found for any of the optic disc parameters. Bland-Altman plots showed good agreement within each operator for calculating scan coordinates suggesting this technique is reproducible.

CONCLUSIONS

Reproducibility of RNFL thickness measurements generally improves with the use of scan tracking coordinates, particularly in the temporal sector. However, small changes in the position of the scan do not significantly affect the reproducibility of optic disc parameters.

Effect of improper scan alignment on retinal nerve fiber layer thickness measurements using Stratus optical coherence tomograph

OBJECTIVE

Misalignment of the Stratus optical coherence tomograph scan circle placed by the operator around the optic nerve head (ONH) during each retinal nerve fiber layer (RNFL) examination can affect the instrument reproducibility and its theoretical ability to detect true structural changes in the RNFL thickness over time. We evaluated the effect of scan circle placement on RNFL measurements.

DESIGN

Observational clinical study.

METHODS

Sixteen eyes of 8 normal participants were examined using the Stratus optical coherence tomograph Fast RNFL thickness acquisition protocol (software version 4.0.7; Carl Zeiss Meditec, Dublin, CA). Four consecutive images were taken by the same operator with the circular scan centered on the optic nerve head. Four images each with the scan displaced superiorly, inferiorly, temporally, and nasally were also acquired. Differences in average and sectoral RNFL thicknesses were determined. For the centered scans, the coefficients of variation (CV) and the intraclass correlation coefficient for the average RNFL thickness measured were calculated.

RESULTS

When the average RNFL thickness of the centered scans was compared with the average RNFL thickness of the displaced scans individually using analysis of variance with post-hoc analysis, no difference was found between the average RNFL thickness of the nasally (105.2 microm), superiorly (106.2 microm), or inferiorly (104.1 microm) displaced scans and the centered scans (106.4 microm). However, a significant difference (analysis of variance with Dunnett's test: F=8.82, P<0.0001) was found between temporally displaced scans (115.8 microm) and centered scans. Significant differences in sectoral RNFL thickness measurements were found between centered and each displaced scan. The coefficient of variation for average RNFL thickness was 1.75% and intraclass correlation coefficient was 0.95.

CONCLUSIONS

In normal eyes, average RNFL thickness measurements are robust and similar with significant superior, inferior, and nasal scan displacement, but average RNFL thickness is greater when scans are displaced temporally. Parapapillary scan misalignment produces significant changes in RNFL assessment characterized by an increase in measured RNFL thickness in the quadrant in which the scan is closer to the disc, and a significant decrease in RNFL thickness in the quadrant in which the scan is displaced further from the optic disc.

An analysis of normal variations in retinal nerve fiber layer thickness profiles measured with optical coherence tomography

PURPOSE

To assess the normal variations in retinal nerve fiber layer (RNFL) thickness measured with optical coherence tomography (OCT).

SUBJECTS AND METHODS

Both eyes of 48 individuals (age 56.4+/-9.5 y) with normal vision and refractive errors between +/-6.0 D were tested with the fast RNFL scan protocol of the OCT3 (Zeiss Meditech). Their 256-point RNFL profiles were exported for analysis. The location and peak amplitude of the maxima of the RNFL profiles were measured. Intersubject and interocular variations were assessed with a coefficient of determination, R2. An R2 of 1.0 indicated that the average profile from all 48 individuals (or of the 2 eyes) accounted for 100% of the variation of an individual eye's profile.

RESULTS

The R2 for the interocular comparison was good, with averages of 0.91+/-0.07 (right eye) and 0.92+/-0.05 (left eye). The R2 for the comparison of the individual's profile to the mean group profile was only 0.61+/-0.29 (right eye) and 0.65+/-0.24 (left eye), with 27% of the R2 values below 0.5. Even after normalizing each individual's profile by its mean, R2 was only 0.75+/-0.16 (0.75+/-0.16) for the right (left) eye. The location of the peaks for the right (left) eye ranged over 91 degrees (88 degrees) for the superior peak and over 64 degrees (66 degrees) for the inferior peak. The range of peak amplitudes for the right (left) eye spanned a factor of 1.7 (1.8) and 2.0 (1.7) for the superior and inferior peaks, respectively.

CONCLUSIONS

There was a wide variation in the amplitude and shape of the individual RNFL profiles. However, the RNFL profiles of the 2 eyes of an individual were extremely similar. Adding an interocular comparison with OCT RNFL tests should help identify some false positives.

Clinical applications and new developments of optical coherence tomography: an evidence-based review

Optical coherence tomography (OCT) is a new imaging modality that has increasingly become an indispensable tool in clinical practice for the diagnosis and management of ocular diseases involving the macula, optic nerve and anterior segment. The instrument is an advanced imaging technique that provides unprecedented high resolution and cross-sectional tomographic images of the ocular microstructure in situ, and in real time. Since its introduction about four years ago, a multitude of advantages has made OCT an essential instrument in ophthalmic imaging. The technique has fast image acquisition speed and non-contact, non-invasive applicability, allowing a non-excisional 'optical biopsy' to be performed. The purpose of this paper is to provide an evidence-based review of the increasing role of OCT in the diagnosis and management of ocular disorders, particularly in age-related macular degeneration, diabetic macular oedema, macular hole, epiretinal membrane and glaucoma. Being one of the first users of OCT in Australia, our clinical experiences will be highlighted and clinical examples of various conditions will be presented to provide an overview of the immense implications of OCT in practice. The latest developments of the OCT revolution, in relation to combining OCT with fundus photography and scanning laser ophthalmoscopy, will also be described. New developments of three-dimensional visualisation of tissue morphology with future models of ultra-high speed, ultra-high resolution OCT may further enhance the early diagnosis, monitoring of disease progression and assessment of treatment efficacy, facilitated by this powerful technology.

Prevalence of myelinated retinal nerve fibres in urban and rural adult Chinese populations: the Beijing Eye Study

PURPOSE

To determine the prevalence of myelinated retinal nerve fibres in the elderly Chinese population.

METHODS

The Beijing Eye Study, a population-based, cross-sectional cohort study, included 4439 subjects out of the 5324 invited to participate (response rate 83.4%) with an age of > 40 years. The present investigation consisted of 8663 eyes of 4378 (98.6%) subjects for whom readable fundus photographs were available.

RESULTS

Myelinated retinal nerve fibres were detected in 35 eyes (29 subjects) with a prevalence rate of 0.4 +/- 6.3%[95% confidence interval (CI): 0.27, 0.54] per eye and 0.7 +/- 8.1% (95% CI: 0.42, 0.90) per subject. The myelinated nerve fibres were located most often in the temporal inferior region, followed by the temporal superior region and the nasal region. Prevalence of myelinated nerve fibres was not associated statistically with age, gender, refractive error, visual acuity (VA), intraocular pressure, cataract, glaucoma and age-related macular degeneration.

CONCLUSION

Myelinated retinal nerve fibres are present in about seven out of 1000 elderly Chinese in northern China, without association to VA, refractive error, glaucoma and macular degeneration.

Retinal nerve fibre thickness measured with optical coherence tomography accurately detects confirmed glaucomatous damage

AIM

To assess the accuracy of optical coherence tomography (OCT) in detecting damage to a hemifield, patients with hemifield defects confirmed on both static automated perimetry (SAP) and multifocal visual evoked potentials (mfVEP) were studied.

METHODS

Eyes of 40 patients with concomitant SAP and mfVEP glaucomatous loss and 25 controls underwent OCT retinal nerve fibre layer (RNFL), mfVEP and 24-2 SAP tests. For the mfVEP and 24-2 SAP, a hemifield was defined as abnormal based upon cluster criteria. On OCT, a hemifield was considered abnormal if one of the five clock hour sectors (3 and 9 o'clock excluded) was at <1% (red) or two were at <5% (yellow).

RESULTS

Seventy seven (43%) of the hemifields were abnormal on both mfVEP and SAP tests. The OCT was abnormal for 73 (95%) of these. Only 1 (1%) of the 100 hemifields of the controls was abnormal on OCT. Sensitivity/specificity (one eye per person) was 95/98%.

CONCLUSIONS

The OCT RNFL test accurately detects abnormal hemifields confirmed on both subjective and objective functional tests. Identifying abnormal hemifields with a criterion of 1 red (1%) or 2 yellow (5%) clock hours may prove useful in clinical practice.