Nerve Fiber Layer Thickness Measurements Research Articles

Effect of signal strength on reproducibility of circumpapillary retinal nerve fiber layer thickness measurement and its classification by spectral-domain optical coherence tomography

To assess the effect of signal strength (SS) on the reproducibility of circumpapillary retinal nerve fiber layer (cpRNFL) thickness measurement (measurement agreement) and its color-coded classification (classification agreement) by Cirrus spectral-domain optical coherence tomography (OCT). Seven hundred and eighty-nine participants, consecutively enrolled from December 2009 to August 2010, underwent two repeated Cirrus OCT scans to measure cpRNFL thickness (optic disc cube 200 × 200). Intraclass correlation (ICC) and linear-weighted kappa coefficient (κ) were calculated as indicators for cpRNFL measurement and classification agreement. The difference in cpRNFL thickness measurements between repeated OCT scans (inter-scan measurement difference) was correlated with mean SS, SS change or difference between repeated OCT scans (inter-scan SS difference), and average cpRNFL thickness. Mean SS was negatively correlated with inter-scan SS difference and was positively correlated with the inter-scan measurement difference. Repeated scans with SS change (inter-scan SS difference = 1 or 2) showed larger variability than scans without SS change (inter-scan SS difference = 0) in total average cpRNFL and all quadrant maps except for the nasal quadrant. Multivariate analysis revealed that inter-scan measurement differences increased in subjects with thinner cpRNFL thicknesses and in scans with lower mean SS and higher inter-scan SS differences. Measurement agreement (ICC) in groups with larger inter-scan SS differences (=2) was lower than those with smaller inter-scan SS differences (=0 or 1) in their average cpRNFL and inferior quadrant maps. Classification agreement (κ) in groups with larger inter-scan SS differences (=2) was lower than those with smaller inter-scan SS differences (=0 or 1) in their average cpRNFL and quadrant maps (superior and inferior quadrant) although statistically not significant. Special attention should be paid when comparing the cpRNFL thickness measurement and color-coded classification of 2 or more Cirrus OCT scans as the agreements may be susceptible to SS differences.

Comparison of two retinal nerve fibre layer thickness measurement patterns of RTvue optical coherence tomography

To evaluate the agreement and repeatability between operator-dependent centring and automatic centring retinal nerve fibre layer thickness measurement patterns (RNFL3.45 and NHM4) of RTvue optical coherence tomography in normal and glaucomatous eyes. Cross-sectional observational study. A total of 153 eyes from 149 normal subjects and subjects with glaucoma were analysed. The retinal nerve fibre layer thickness was measured using RNFL3.45 and NHM4 three times on the same day to determine the repeatability and agreement between the two scan patterns. Student's paired t-testing, intra-class correlation coefficient, coefficient of variation, test-retest viability, Pearson's correlation coefficient and Bland-Altman analysis of retinal nerve fibre layer thickness measurements. The difference between RNFL3.45 and NHM4 measurements was statistically significant by paired t-testing (P=0.003) only in severe glaucoma group. The Pearson's correlation test showed a high degree of correlation of the mean retinal nerve fibre layer thickness (r=0.949). Bland-Altman plots showed that the differences between RNFL3.45 and NHM4 were smaller at thicker retinal nerve fibre layer values, but larger at thinner retinal nerve fibre layer values. The intra-class correlation coefficient for RNFL3.45 (and lower 95% confidence interval) in normal and glaucomatous eyes was 0.990 (0.985 confidence interval) and 0.997 (0.995 confidence interval), respectively. The intra-class correlation coefficient for NHM4 in normal and glaucomatous eyes was 0.989 (0.983 confidence interval) and 0.995 (0.992 confidence interval), respectively. The test-retest variability for RNFL3.45 and NHM4 ranged from 3.98 to 9.75µm in normal eyes, and from 4.10 to 13.34µm in glaucomatous eyes. Measurements of retinal nerve fibre layer thickness by RNFL3.45 and NHM4 are in good agreement.

The Use of HRT With and Without the Aid of Disc Photographs

To evaluate the measurement of optic disc morphology using Heidelberg Retinal Tomography (HRT) with and without the aid of optic disc photos. One hundred three children (aged 11 and 12 y, 52 boys) were selected randomly from the Singapore Cohort study of Risk Factors for Myopia. Optic nerve head topography and retinal nerve fiber layer thickness measurements were assessed using the HRT-II (Heidelberg, Germany) scanning laser ophthalmoscope. All contour lines were drawn by the same researcher on 2 occasions. The first drawing was made without optic disc photographs but using the 3-dimensional rotation assessment. The second drawing was made with the additional aid of digital monoscopic optic disc photographs. There was a high correlation between the measurements taken with and without optic disc photographs. For the global disc area, the difference between the mean readings was 0.67 mm and the intraclass correlation (ICC) was 0.81 [95% confidence interval (CI) 0.73-0.86]. The mean difference for the global cup-to-disc ratio was 0.03 [ICC 0.86 (95% CI 0.80-0.90)]. The ICCs were high across almost all of the readings except rim volume, in which the ICC was 0.57 (95% CI 0.43-0.69). This study shows minimal differences in HRT measured optic disc parameters when optic disc photos are used to aid in the definition of the scleral ring. Omitting the use of disc photographs in measuring HRT outputs may translate into significant savings in time and logistics in simultaneously obtaining HRT and optic disc photographs in large population-based studies.

Image Quality Affects Macular and Retinal Nerve Fiber Layer Thickness Measurements on Fourier-Domain Optical Coherence Tomography

To investigate whether image quality is an important determinant of retinal nerve fiber layer (RNFL) and macular thickness measurements on Fourier-domain optical coherence tomography (OCT). Seventy-five and 56 normal subjects were recruited in RNFL and macular thickness arms of the study, respectively. Each participant was scanned three times using both the 3D OCT-1000 (version 3.01, Mark II; Topcon Corporation, Tokyo, Japan) and the Cirrus OCT (version 3.0, Model 4000; Carl Zeiss Meditec, Inc., Dublin, CA). The scans for each participant were arranged in order of increasing image qualities, which were correlated with RNFL and macular thicknesses. Subgroup analyses were performed with identical versus different and high versus low image quality metrics. Higher image quality was significantly correlated with greater RNFL thickness measurements on the 3D OCT-1000, and when the signal strength was less than 7 on the Cirrus device. Image quality metrics were negatively correlated with measured macular thicknesses on Cirrus OCT but not on 3D OCT-1000. Image quality metrics should be considered when evaluating thickness measurements derived from Fourier-domain OCT devices.

Association of Birth Parameters with OCT Measured Macular and Retinal Nerve Fiber Layer Thickness

To examine whether birth parameters have associations with macular and retinal nerve fiber layer (RNFL) thickness measurements. The Sydney Myopia Study examined secondary school children for ocular conditions, with all eligible year 7 students from 21 high schools invited to participate. Macular and RNFL measurements were acquired from optical coherence tomography (OCT) scans. Birth variables, including birth weight and gestational duration, were obtained from parental questionnaires and health records. Mixed linear models were used in analyses, after adjustment for age, sex, height, axial length, and ethnicity. In children with complete gestational duration data, adequate quality scans of the RNFL and macula were obtained from 1756 and 1698 children, respectively. Children with low birth weight (<2500 g) had a thinner mean RNFL (98.2 μm vs. 103.5 μm; P < 0.0001) and a thicker mean foveal minimum (164.3 μm vs. 158.5 μm; P = 0.004) than did children of normal birth weight (2500-4000 g). With increasing birth weight, average RNFL thickness increased (mixed model coefficient, β = 2.97 μm/kg; P < 0.0001) and foveal minimum thickness decreased (β = -2.16 μm/kg; P = 0.008). Children born before 32 weeks' gestation had significantly thicker mean foveal minimum and central macular thickness (205.5 μm vs. 193.4 μm; P = 0.001) measurements than did children born after 37 weeks' gestation. Low birth weight and prematurity are associated with thickening of the fovea, and decreased birth weight is associated with decreased RNFL thickness, as measured by OCT. These findings suggest that premature birth and low birth weight impair retinal development and may predispose these children to ocular problems later in life.

Comparison of the Diagnostic Accuracies of the Spectralis, Cirrus, and RTVue Optical Coherence Tomography Devices in Glaucoma

To compare the diagnostic accuracies of retinal nerve fiber layer (RNFL) thickness measurements obtained with the Spectralis (Heidelberg Engineering, Dossenheim, Germany), Cirrus (Carl Zeiss Meditec, Dublin, CA), and RTVue (Optovue Inc., Fremont, CA) devices for the detection of glaucoma. Diagnostic, case-control study. A total of 233 (107 healthy, 126 glaucomatous) of 149 participants from the longitudinal Diagnostic Innovations in Glaucoma Study (DIGS) and from the African Descent and Glaucoma Evaluation Study (ADAGES). All participants underwent RNFL thickness imaging with the Spectralis, Cirrus, and RTVue devices in the same visit. Receiver operating characteristic (ROC) curves adjusted for age and race were obtained for quadrants (superior, nasal, inferior, temporal) and global RNFL thickness for all instruments. Areas under ROC (AUC) and sensitivities at fixed specificities (80% and 95%) were calculated and compared. Comparison of diagnostic accuracy using AUCs and sensitivities at fixed specificities of 80% and 95%. The RNFL thickness parameter with the largest AUCs was the superior quadrant for the Spectralis (0.88) and the global RNFL thickness for the Cirrus (0.88) and the RTVue (0.87). The pairwise comparison among the ROC curves showed no statistical difference for all parameters except for the nasal quadrant, which had significantly larger AUC in the Spectralis and RTVue compared with the Cirrus (P<0.03 for both comparisons). There were no significant differences in sensitivities among the best parameters from each instrument (P>0.05). The superior quadrant thickness measured with the Spectralis had sensitivity of 81.9% at a fixed specificity of 80% and 70% at a fixed specificity of 95%. The global thickness measured by the Cirrus had a sensitivity of 80.3% at a fixed specificity of 80% and 65.6% at a fixed specificity of 95%. For the RTVue, the global thickness had a sensitivity of 77.9% at a fixed specificity of 80% and 62.1% at a fixed specificity of 95%. Although the spectral-domain optic coherence tomography (SD-OCT) instruments have different resolution and acquisition rates, their ability to detect glaucoma was similar.

Effect of Contact Lens Power on Optical Coherence Tomography of the Retinal Nerve Fiber Layer

To study the effect of contact lens (CL) power on retinal nerve fiber layer (RNFL) thickness measurements using optical coherence tomography (OCT). Cross-sectional study on 15 healthy subjects. Peripapillary RNFL thickness was measured using time-domain OCT without CL and with CL of different powers (+4 D, +10, -4D, and -10 D), and again without CL. RNFL thickness measurements were compared statistically. Age of study subjects was 30.5 ± 3.2 (mean ± SD) years. Global RNFL thickness measurements showed good repeatability (average without CL was 107 ± 9.3 μm for the first measurement, and 107.4 ± 7.4 μm for the second [P = 0.8]). There was no significant effect of CL power on global RNFL thickness, although more variability was observed with the -10 D CL. When analyzing individual clock-hour segments, only differences in the 6 o'clock hour segment were statistically significant (between -10 D CL [155.9 ± 22.4 μm] and without CL [143.5 ± 19.3 μm], as well as between -10 D and +4 D CL [138.9 ± 19.9 μm], with P < 0.001). When analyzed for individual quadrants, differences in the inferior quadrant were significant between measurements with -10 D CL and all other CLs. Refractive error changes at the corneal plane do not significantly affect RNFL thickness measurements using OCT; caution is warranted in inferior segments, where variations may occur. These results may be applicable to RNFL thickness measurements before and after cataract or refractive surgery.

The influence of axial length on retinal nerve fibre layer thickness and optic-disc size measurements by spectral-domain OCT

BackgroundTo evaluate the influence of axial length on measurements of the retinal nerve fibre layer (RNFL) thickness and optic nerve head (ONH) parameters in healthy subjects.MethodsUsing Cirrus HD-OCT, RNFL thickness...

Macular and Retinal Nerve Fiber Layer Thickness Measurements in Normal Eyes With the Stratus OCT, the Cirrus HD-OCT, and the Topcon 3D OCT-1000

To compare retinal nerve fiber layer (RNFL) and macular thickness measurements using time-domain optical coherence tomography (TD OCT) and 2 Fourier-domain OCTs (FD OCT). Sixty eyes of 60 normal participants underwent eye examination followed by OCT evaluation with the time-domain Stratus OCT (Carl Zeiss Meditec, Inc. Dublin, CA) and 2 FD OCTs-the Cirrus HD-OCT (Carl Zeiss Meditec, Inc. Dublin, CA) and the 3D OCT-1000 (Topcon Corporation, Tokyo, Japan). Each patient was scanned 3 times on each machine by the same physician examiner. RNFL and macular thickness measurements were compared across the 3 devices using repeated measures analysis of variance (ANOVA) and multiple comparison t tests with Bonferroni adjustments. The coefficients of variation (CV) and the intraclass correlation coefficients were calculated to assess reproducibility. Bland-Altman plots were constructed to assess the level of agreement between every 2 OCTs. All 3 machines revealed similar patterns of regional differences in RNFL and macular thicknesses. Macular thickness was consistently greatest on the Cirrus and lowest on the Stratus device. However, RNFL measurements were less consistent. The overall average RNFL thickness was 4 μm greater on the Stratus than on the 3D OCT-1000, which was in turn 5 μm greater than on the Cirrus device. Bland-Altman plots showed poor-to-moderate agreement in terms of macular and RNFL thickness measurements between each 2 of the OCT devices. Both FD OCTs provided more reproducible readings on macular measurements than the Stratus, as evidenced by the lower CV and higher intraclass correlation coefficients. However, RNFL measurements on the 2 FD OCTs were not necessarily more reproducible than those from the Stratus OCT. Thickness measurements are not interchangeable among different OCT devices because of the poor-to-moderate interdevice measurement agreement. FD instruments yield more reproducible macular but not RNFL thickness measurements.

Automatic, Operator-adjusted, and Manual Disc-definition for Optic Nerve Head and Retinal Nerve Fiber Layer Measurements With the RTVue-100 Optical Coherence Tomograph

To evaluate the repeatability and between-methods differences of optic nerve head and retinal nerve fiber layer thickness (RNFLT) measurements as made with the automatic, operator-adjusted, and manual disc-definition functions of the RTVue-100 Fourier-domain optical coherence tomograph. One eye of each of 126 persons (72 glaucomatous, 10 ocular hypertensive, 44 healthy control eyes) was analyzed with all 3 disc-definition functions. Thirty-three eyes were imaged 5 times for the determination of measurement repeatability. For several parameters, repeatability with automatic disc definition was significantly poorer than the other options. In contrast, for all but 1 parameter repeatability did not differ between the manual and operator-adjusted methods. Refractive error, disease category or peripapillary atrophy had no influence on repeatability. However, the measured values differed significantly between the methods, for all but 3 parameters. Similar between-method differences were seen for eyes irrespective of glaucoma, refractive error, or parapapillary atrophy. High intraclass correlation (93.5% to 99.9%) was seen for all parameters measured with manual and operator-adjusted methods, but in the other comparisons only for RNFLT parameters. Agreement of the classifications was better for RNFLT parameters than disc parameters, and the κ-values were highest (0.881 to 0.968) in comparing the manual and operator-adjusted methods. Measurement repeatability with manual and operator-adjusted disc-definition functions is similar and is not influenced by refractive error, glaucoma, or parapapillary atrophy. The high intraclass correlation and the agreement of diagnostic classifications suggest that operator-adjusted disc-definition can be useful for glaucoma detection with the RTVue-100 Fourier-domain optical coherence tomograph.

Comparison of the influence of cataract and pupil size on retinal nerve fibre layer thickness measurements with time-domain and spectral-domain optical coherence tomography

To investigate and compare the effect of cataract and pupil size on retinal nerve fibre layer (RNFL) thickness measurements using spectral-domain optical coherence tomography (Cirrus OCT) and time-domain OCT (Stratus OCT). Prospective, hospital-based study. Twenty-five eyes from 25 normal subjects undergoing cataract surgery. Three retinal nerve fibre layer (RNFL) thickness measurements were taken before and after dilation, preoperatively and postoperatively, using Cirrus 200×200 Optic Disc Scan and Stratus Fast RNFL Scan. Linear regression, intraclass correlation coefficient (ICC) and coefficient of variation analysis. Cataract removal caused significant increase in RNFL measurements in both modalities (Cirrus P<0.02; Stratus P<0.001). There was no significant difference in the increase in measurements between the two machines. Pupil dilation had variable and non-statistically significant effect in both (P>0.05). ICC showed excellent reproducibility with Cirrus OCT after mydriasis, preoperatively (ICC=0.78-0.90) and postoperatively (ICC=0.90-0.97), but poor reproducibility before mydriasis (P<0.75). Stratus OCT achieved excellent reproducibility after cataract removal both before (ICC=0.86-0.96) and after mydriasis (ICC=0.92-0.95), but poor reproducibility before cataract surgery (P<0.75). Cataracts, not pupil size, cause significant underestimation of RNFL measurements in both Cirrus and Stratus OCT. The extent of influence exerted does not appear different between the two instruments. Reproducibility of each machine appears to be affected differently. Mydriasis is required to achieve excellent reproducibility with Cirrus OCT, and media clarity is required with Stratus OCT.

Reproducibility of peripapillary retinal nerve fibre layer thickness measurements with spectral domain optical coherence tomography in normal and glaucomatous eyes

AimTo determine reproducibility of peripapillary retinal nerve fibre layer thickness (RNFLT) measurements by spectral optical coherence tomography scanning laser ophthalmoscope (Spectral OCT/SLO) in normal and glaucomatous eyes.Methods61 normal subjects and...

Ability of spectral domain optical coherence tomography peripapillary retinal nerve fiber layer thickness measurements to identify early glaucoma

Purpose:To evaluate the ability of spectral domain optical coherence tomography (OCT) peripapillary retinal nerve fiber layer thickness (RNFLT) parameters to distinguish normal eyes from those with early glaucoma in Asian Indian eyes.Design:Observational cross-sectional study.Materials and Methods:One hundred and seventy eight eyes (83 glaucoma patients and 95 age matched healthy subjects) of subjects more than 40 years of age were included in the study. All subjects underwent RNFLT measurement with spectral OCT/ scanning laser ophthalmoscope (SLO) after dilatation. Sensitivity, specificity and area under the receiving operating characteristic curve (AROC) were calculated for various OCT peripapillary RNFL parameters.Results:The mean RNFLT in healthy subjects and patients with early glaucoma were 105.7 ± 5.1 μm and 90.7 ± 7.5 μm, respectively. The largest AROC was found for 12 o’clock- hour (0.98), average (0.96) and superior quadrant RNFLT (0.9). When target specificity was set at ≥ 90% and ≥ 80%, the parameters with highest sensitivity were 12 o’clock -hour (91.6%), average RNFLT (85.3%) and 12 o’ clock- hour (96.8 %), average RNFLT (94.7%) respectively.Conclusion:Our study showed good ability of spectral OCT/ SLO to differentiate normal eyes from patients with early glaucoma and hence it may serve as an useful adjunct for early diagnosis of glaucoma.

Inter-Device Agreement of Retinal Nerve Fiber Layer Thickness Measurements Using Spectral Domain Cirrus HD OCT

PurposeTo assess the inter-device agreement of peripapillary retinal nerve fiber layer (RNFL) thickness measurements by 2 spectral domain Cirrus HD optical coherence tomography (OCT) devices in healthy Korean subjects.MethodsEleven eyes of 11 healthy volunteers were enrolled in the present study. Each eye was scanned with the Optic Disc Cube 200 × 200 scan of 2 Cirrus HD OCT devices for peripapillary RNFL thickness calculation. The inter-device agreements of the 2 Cirrus HD OCTs for average, quadrant, and clock-hour RNFL thickness values were determined with Wilcoxon signed rank test, Friedman test, Cronbach's alpha (α), intraclass correlation coefficient (ICC), coefficient of variation (COV), and Bland-Altman plot.ResultsThe mean age of the participants was 25.82 ± 3.28 years and all had a 0.00 logarithm of the minimum angle of resolution of best-corrected visual acuity. The signal strengths of scans from the 2 Cirrus HD OCT were not significantly different (p = 0.317). The inter-device agreement of average RNFL thickness was excellent (α, 0.940; ICC, 0.945; COV, 2.45 ± 1.52%). However, the agreement of nasal quadrant RNFL thickness was not very good (α, 0.715; ICC, 0.716; COV, 5.72 ± 4.64%). Additionally, on the Bland-Atman plot, the extent of agreement of the 2 Cirrus HD OCTs for RNFL thickness was variable according to scanned sectors.ConclusionsThe inter-device agreement of 2 spectral domain Cirrus HD OCT devices for peripapillary RNFL thickness measurements was generally excellent but variable according to the scanned area. Thus, physicians should consider this fact before judging a change of RNFL thicknesses if they were measured by different OCT devices.

Comparison of retinal nerve fiber layer measured by time domain and spectral domain optical coherence tomography in optic neuritis

To study the relationship between retinal nerve fiber layer (RNFL) thickness measurements from time domain (Stratus) and spectral domain (Cirrus HD) optical coherence tomography (OCT) in subjects with optic neuritis. A total of 18 patients who had suffered monocular acute optic neuritis were imaged by a single trained operator using the Stratus-OCT (fast RNFL scan mode) and Cirrus HD-OCT (optic disc cube mode) on the same day. The relationship between RNFL thickness measurements of the two OCTs (overall and by quadrants) were evaluated using intraclass correlation coefficient (ICC) and Bland-Altman plots. Comparisons between eyes having optic neuritis (ON-group) and fellow eyes (fellow-group) were assessed by a generalized estimating equation (GEE) regression model. For Stratus-OCT, the median average RNFL was 86.3 and 102 μ in the ON-group and in the fellow-group, respectively. For Cirrus-OCT, the corresponding measurements were 81 and 93 μ. Average RNFL thickness as determined by the two OCT devices was well correlated in the ON-group (ρ = 0.906, P< 0.001) and in the fellow-group (ρ = 0.702, P = 0.001). The median signal strength was significantly higher with Cirrus-OCT. Bland-Altman plots showed that Stratus RNFL measurements were larger than Cirrus-OCT, but smaller when average RNFL thickness was very thin (≤ 56 μ). Although the Cirrus-OCT and Stratus-OCT RNFL thickness measurements are well correlated in patients with optic neuritis, RNFL measurements cannot be directly compared. Clinicians should be aware that measurements are generally higher with Stratus- than with Cirrus-OCT.

Ocular Changes Associated with Topiramate

Purpose: To determine the changes in refractive error, and the cornea, anterior chamber, and retina induced by topiramate.Methods: The study included 76 eyes of 38 patients that began to use topiramate due to migraine. Following ophthalmological examination, all of the patients underwent central corneal thickness (CCT), anterior chamber volume (ACV), anterior chamber depth (ACD), and anterior chamber angle (ACA) measurement using a Scheimpflug camera, as well as macular thickness, retinal and retinal nerve fiber layer thickness (RNFLT) measurements using optical coherence tomography (OCT). These procedures were repeated 15, 30, and 90 days after the initiation of topiramate therapy.Results: The median refractive error value showed a statistically significant increase from −0.25 diopters (D) to −0.62 D at the 90th day follow-up (P < 0.001). Mean CCT was 570.56 µm before treatment and increased to 573.69 µm at the 15th day follow-up, 575.31 µm at the 30th day follow-up, and 574.56 µm at the 90th day follow-up; however, these changes were not statistically significant. Mean ACV, ACD, and ACA did not exhibit statistically significant changes. Mean retinal thickness (RT) increased during the treatment from 263.46 µm to 271.60 µm, which was not statistically significant. The initial mean RNFLT was 100.56 ± 15.36 µm and significantly increased to 110.2 ± 8.41 µm and 111.03 ± 14.59 µm at the 30th and 90th day follow-ups, respectively (P = 0.01 and P = 0.004, respectively).Conclusions: During the 3-month follow-up of patients using topiramate 50 mg d−1 significant myopic shift and an increase in RNFLT were observed. Further studies are warranted in order to assess the effects of topiramate when used long term and at higher doses.

Reproducibility of Retinal Nerve Fiber Thickness Measurements Using the Test-retest Function of Spectral OCT/SLO in Normal and Glaucomatous Eyes

To evaluate the reproducibility of retinal nerve fiber layer (RNFL) thickness measurements in normal and glaucoma patients using the spectral optical coherence tomography (OCT)/scanning laser ophthalmosope (SLO). One experienced operator measured peripapillary RNFL thickness 3 times in succession in 98 normal participants and 79 glaucoma patients by using the test-retest function of the spectral OCT/SLO. The intraclass correlation coefficient (ICC), coefficient of variation, and test-retest variability (TRV) were analyzed for the mean RNFL thickness, and the RNFL thickness in each quadrant and at each clock-hour, in randomly selected eyes. The correlation coefficient was calculated between the TRV and the mean RNFL thickness, and between the TRV and the mean deviation of the Humphrey visual field. The ICC for mean RNFL thickness was 0.988 in the normal group and 0.993 in the glaucoma group. The ICC for RNFL thickness in all quadrants and clock-hours in both normal and glaucoma patients ranged from 0.951 to 0.992. The coefficient of variation was between 1.9% and 5.0% in the normal group and between 2.0% and 5.3% in the glaucoma group. The TRV was between 4.3 and 11.5 μm in the normal group and between 3.8 and 10.0 μm in the glaucoma group. The TRV showed no correlation with the mean RNFL thickness or the mean deviation (Pearson r>0.15, P>0.2). Spectral OCT/SLO equipped with a test-retest function showed excellent reproducibility with regard to RNFL thickness measurements. The severity of glaucoma did not affect the reproducibility. These findings suggest that spectral OCT/SLO fulfills one of the basic premises for the diagnosis and progression analysis of glaucoma.

Frequency doubling technique perimetry and spectral domain optical coherence tomography in patients with early glaucoma

To assess the combined diagnostic power of frequency-doubling technique (FDT)-perimetry and retinal nerve fibre layer (RNFL) thickness measurements with spectral domain optical coherence tomography (SDOCT). The study included 330 experienced participants in five age-related groups: 77 'preperimetric' open-angle glaucoma (OAG) patients, 52 'early' OAG, 50 'moderate' OAG, 54 ocular hypertensive patients, and 97 healthy subjects. For glaucoma assessment in all subjects conventional perimetry, evaluation of fundus photographs, FDT-perimetry and RNFL thickness measurement with SDOCT was done. Glaucomatous visual field defects were classified using the Glaucoma Staging System. FDT evaluation used a published method with casewise calculation of an 'FDT-score', including all missed localized probability levels. SDOCT evaluation used mean RNFL thickness and a new individual SDOCT-score considering normal confidence limits in 32 sectors of a peripapillary circular scan. To examine the joined value of both methods a combined score was introduced. Significance of the difference between Receiver-operating-characteristic (ROC) curves was calculated for a specificity of 96%. Sensitivity in the preperimetric glaucoma group was 44% for SDOCT-score, 25% for FDT-score, and 44% for combined score, in the early glaucoma group 83, 81, and 89%, respectively, and in the moderate glaucoma group 94, 94, and 98%, respectively, all at a specificity of 96%. ROC performance of the newly developed combined score is significantly above single ROC curves of FDT-score in preperimetric and early OAG and above RNFL thickness in moderate OAG. Combination of function and morphology by using the FDT-score and the SDOCT-score performs equal or even better than each single method alone.

Interpretation of RNFLT values in multiple sclerosis‐associated acute optic neuritis using high‐resolution SD‐OCT device

Optical coherence tomography (OCT) has emerged as the technique of choice in measuring the retinal nerve fibre layer (RNFL) quantitatively. It is suggested that RNFL reduction may correlate with lesion burden and diffuse axonal degeneration in the whole CNS of patients with multiple sclerosis (MS). However, RNFL changes because of optic neuritis (ON) must be taken into account. Twenty-three patients with acute ON (46 eyes) associated with clinical definite MS (23 ON eyes, 23 fellow eyes) and 23 sex- and age-matched healthy controls were studied. Retinal nerve fibre layer thickness (RNFLT) was measured at baseline, using a high-resolution spectral domain OCT (SD-OCT) applying circular, peripapillary OCT scans with a novel eye-tracking mechanism. The internal OCT software was able to identify RNFL atrophy in three out of five of the acute ON eyes and one out of four of the fellow eyes with previous ON episodes. Retinal nerve fibre layer thickness of two ON (8.7%) and five fellow eyes (21.7%) was overestimated, thus located within the 95% and 5% confidence interval of the company standard values (not marked pathologic). In contrast, our comparison with age- and sex-matched controls revealed RNFL atrophy suggestive of prior, clinically silent RNFL loss in ON and fellow eyes (30.4%). Retinal nerve fibre layer thickness measurements at a single time-point seem to have a limited role in detecting prior clinically silent optic nerve injury. Our data suggest that affected eyes should be compared with the fellow eyes and a sufficient number of age- and sex-matched controls to allow the detection of even subtle RNFL changes at baseline. The role of OCT for disease monitoring of MS must be evaluated in detail, as ON is often the initial symptom of MS.

Agreement Among Spectral-Domain Optical Coherence Tomography Instruments for Assessing Retinal Nerve Fiber Layer Thickness

To assess the agreement of parapapillary retinal nerve fiber layer (RNFL) thickness measurements among 3 spectral-domain optical coherence tomography (SD-OCT) instruments. Observational, cross-sectional study. Three hundred thirty eyes (88 with glaucoma, 206 glaucoma suspects, 36 healthy) from 208 individuals enrolled in the Diagnostic Innovations in Glaucoma Study (DIGS) were imaged using RTVue, Spectralis and Cirrus in a single visit. Agreement among RNFL thickness measurements was assessed using Bland-Altman plots. The influence of age, axial length, disc size, race, spherical equivalent, and disease severity on the pairwise agreements between different instruments was assessed by regression analysis. Although RNFL thickness measurements between different instruments were highly correlated, Bland-Altman analyses indicated the presence of fixed and proportional biases for most of the pairwise agreements. In general, RTVue measurements tended to be thicker than Spectralis and Cirrus measurements. The agreement in average RNFL thickness measurements between RTVue and Spectralis was affected by age (P = .001) and spherical equivalent (P < .001), whereas the agreement between Spectralis and Cirrus was affected by axial length (P = .004) and spherical equivalent (P < .001). Disease severity influenced the agreement between Spectralis and both RTVue and Cirrus (P = .001). Disc area and race did not influence the agreement among the devices. RNFL thickness measurements obtained by different SD-OCT instruments were not entirely compatible and therefore they should not be used interchangeably. This may be attributable in part to differences in RNFL detection algorithms. Comparisons with histologic measurements could determine which technique is most accurate.