Spectral Optical Coherence Tomography System Research Articles

Retinal single-layer analysis with optical coherence tomography (OCT) in schizophrenia spectrum disorder

Introduction Volume reductions in brain structures of patients with schizophrenia spectrum disorder (SSD) have repeatedly been found in voxel-based morphometry MRI studies. Hence, an underlying neurodegenerative etiological component of SSD is currently being discussed. In recent years, the imaging method of optical coherence tomography (OCT) has shown its potential in evaluating structural changes in the retina in patients with confirmed neurodegenerative disorders, providing a window into the brain.ObjectivesTo evaluate potential differences in measurements of retinal layers between patients with schizophrenia spectrum disorder and healthy controls with OCT.MethodsTwenty-six patients with schizophrenia or schizoaffective disorder and 23 age- and sex-matched healthy controls were examined with the Heidelberg Spectralis OCT system to derive a single-layer analysis of both retinas. The segmentation of retinal layers was manually corrected to minimize artifacts and software imprecisions.ResultsCompared to the control group, SSD patients showed reduced thickness and volume measurements for nearly all retinal layers, and these differences reached significance for macular volume, macular thickness, retinal nerve fiber layer (RNFL) and inner nucleiform layer (INL). Furthermore, a significant correlation between the duration of illness and the total volume of the RNFL was found.ConclusionsOur OCT measurements demonstrate reduced single retinal layer thickness in patients with SSD. In the context of the MRI volume changes, our results provide further evidence that structural changes seen in the brain of patients are also observable in the retina, potentially allowing further insights into the different components of the nervous system that are altered in this highly etiologically complex disorder.DisclosureNo significant relationships.

Correlation of chorioretinal parameters with anatomical, optical and functional indicators of eyes with amblyopia of various origins

The study included 50 patients aged 5 to 16 years (mean age 10.04±3.01 years). All patients were divided into 6 groups: 1 - relative amblyopia with congenital myopia (23 eyes); 2 - dysbinocular amblyopia (14 eyes); 3 - refractive amblyopia (16 eyes); 4 - anisometropic amblyopia (7 eyes); 5 - paired eyes of patients with amblyopia (20 eyes); 6 - control group (20 eyes). Chorioretinal parameters were determined using the RS-3000 Advance 2 spectral optical coherence tomography system («Nidek», Japan). Correlation analysis was performed using the Pearson's linear correlation coefficient (r). The level of significance of the differences was determined by the standard Student's t-test. Morphological changes in the sensory and choroid membranes of the eye were revealed in groups with amblyopia of various origins compared to the control group, as well as in the fellow eyes. Intergroup comparison showed the presence of more significant disorders in refractive and relative amblyopia due to congenital myopia. Correlation analysis showed that structural changes in the posterior pole are more related to the anatomical and optical parameters of the eyes. Optical coherence tomography allows detection of microscopic structural anomalies in the posterior pole of the eye in amblyopia of various origins, assists in differential diagnosis of this condition with organic pathology, and - most importantly - helps peer deeper into the pathogenesis of this disease.

Evaluation of the influence of scattered radiation on image quality in spectral optical coherence tomography systems with electronic scanning of objects

A comparative evaluation of the influence of scattered radiation on the quality of generated tomographic images in spectral optical coherence tomography systems with a tunable wavelength is presented. Simulation and experimental results demonstrate that systems with a linear illumination field provide a high operating speed and reduce the noise component of the image by about half compared with the full-field method when a tomographic image of a scattering object is obtained.

Retinal single-layer analysis with optical coherence tomography (OCT) in schizophrenia spectrum disorder

BackgroundVolume reductions in brain structures of patients with schizophrenia spectrum disorder (SSD) have repeatedly been found in voxel-based morphometry MRI studies. Hence, an underlying neurodegenerative etiological component of SSD is currently being discussed. In recent years, the imaging method of optical coherence tomography (OCT) has shown its potential in evaluating structural changes in the retina in patients with confirmed neurodegenerative disorders, providing a window into the brain. MethodsTwenty-six patients with schizophrenia or schizoaffective disorder and 23 age- and sex-matched healthy controls were examined with the Heidelberg Spectralis OCT system to derive a single-layer analysis of both retinas. The segmentation of retinal layers was manually corrected to minimize artifacts and software imprecisions. ResultsCompared to the control group, SSD patients showed reduced thickness and volume measurements for nearly all retinal layers, and these differences reached significance for macular volume, macular thickness, retinal nerve fiber layer (RNFL) and inner nucleiform layer (INL). Furthermore, a significant correlation between the duration of illness and the total volume of the RNFL was found. ConclusionOur OCT measurements demonstrate reduced single retinal layer thickness in patients with SSD. In the context of the MRI volume changes, our results provide further evidence that structural changes seen in the brain of patients are also observable in the retina, potentially allowing further insights into the different components of the nervous system that are altered in this highly etiologically complex disorder.

Energetic efficiency assessment of spectral coherence tomograph optical-electronic system

Subject of Research.The paper considers the methods of optical coherence tomography (OCT) based on illuminating a sample by optical radiation with subsequent determination of light reflection degree through a sample depth. Illumination method defines basic characteristics of OCT system such as sensitivity and speed in studies of biological samples. In mechanical scanning-free OCT systems, line- and full-field illumination methods are applied utilizing object illumination by laser source with tunable wavelength. The study is aimed at energetic efficiency quantitative assessment of line-field OCT system with tunable radiation source and in comparison of line-field illumination method with full-field one. Method. Based on the model of OCT optical system, ray tracing has been carried out, and spatial distribution of energy reflected from a sample and registered by photo detector has been determined. Photoelectrical signal and signal-to-noise ratio have been evaluated.Main Results. It has been shown that line-field OCT system providessignificantly higher sensitivity (97 dB) compared to full-field system (78 dB). In addition, line-field system allows obtaining B-scan without moving of mechanical parts. Original scheme of lighting channel has been proposed providing uniform illumination spatial distribution along lighting line without sensitivity decay near edges of image field. Practical Relevance.The obtained results can be applied for creation of compact real-time spectral OCT system.

In vivo exploration of retinal nerve fiber layer morphology in Parkinson's disease patients.

Thinning of the retinal nerve fiber layer (RNFL) is a recently discovered feature of Parkinson's disease (PD). Its exact pathological mechanism is yet unknown. We aimed to determine whether morphological changes of the RNFL are limited to RNFL thinning or also comprise an altered internal structure of this layer. Therefore, we investigated RNFL thickness and applied the RNFL attenuation coefficient (RNFL-AC), a novel method derived from optical coherence tomography, in PD patients and healthy controls (HCs). In this pilot study, we included 20 PD patients and 20 HCs matched for age, sex, and ethnicity. An ophthalmologist investigated all participants thoroughly, and we acquired retinal images from both eyes of each participant with a Spectralis optical coherence tomography system. We obtained both the RNFL-AC and RNFL thickness from peripapillary RNFL scans for the entire RNFL, as well as for each quadrant separately. We found no significant differences in the average RNFL-AC or the RNFL-AC of the separate retinal quadrants between PD patients and the HC group. However, compared to the HC group, PD patients had a significantly thinner RNFL in the temporal retinal quadrant. RNFL thinning was found in the temporal quadrant in PD patients without a corresponding change in the RNFL-AC. These findings suggest a reduction in the number of RNFL axons (atrophy) without other major changes in the structural integrity of the remaining RNFL.

Repeatability and reproducibility of automatic segmentation of retinal layers in healthy subjects using Spectralis optical coherence tomography.

To evaluate the repeatability and reproducibility of automatic segmentation in healthy subjects using a Spectralis optical coherence tomography (OCT) system. A total of 60 eyes from 60 patients were included in this prospective study. Spectral-domain optical coherence tomography images were generated using the Spectralis OCT system. An automated algorithm was used to segment the macular retina into nine layers and evaluate the thickness of each layer in the foveal, inner, and outer Early Treatment Diabetic Retinopathy Study (ETDRS) subfield rings. The eyes were imaged three times by an examiner to assess intraobserver repeatability and imaged once by a second examiner to assess interobserver reproducibility. The first scan was used for reference, whereas the second and third scans were collected using the device's follow-up mode. Intraclass correlation coefficients (ICCs) of repeatability and reproducibility were analyzed. The examiners achieved high repeatability and reproducibility for all parameters. Good agreement was found for all parameters in all ETDRS subdivisions with an ICC of >0.96 for all measurements. It is possible to obtain cross-sections from the same location using the device's follow-up mode, making it virtually impossible to distinguish between repeated measurements taken with the device by different examiners.

Retinal Blood Flow Response to Hyperoxia Measured With En Face Doppler Optical Coherence Tomography

PurposeTo use multiplane en face Doppler optical coherence tomography (OCT) to measure the change in total retinal blood flow (TRBF) in response to hyperoxia.MethodsOne eye of each healthy human participant (n = 8) was scanned with a commercial high-speed (70-kHz) spectral OCT system. Three repeated scans were captured at baseline and after 10 minutes of oxygen (hyperoxia) by open nasal mask. The procedure was performed twice on day 1 and once more on day 2. Blood flow of each vein was estimated using Doppler OCT at an optimized en face plane. The TRBF was summed from all veins at the optic disc. The TRBF hyperoxic response was calculated as the TRBF percent change from baseline.ResultsParticipants experienced a 23.6% ± 10.7% (mean ± standard deviation [SD]) decrease (P < 0.001, paired t-test) in TRBF during hyperoxia. The within-day repeatability of baseline TRBF was 4.1% and the between-day reproducibility was 10.9% coefficient of variation (CV). Between-grader reproducibility was 3.9% CV. The repeatability and reproducibility (pooled SD) of hyperoxic response were 6.1% and 6.4%, respectively.ConclusionsThe multiplane en face Doppler OCT algorithm was able to detect, in all participants, a decreased TRBF in response to hyperoxia. The response magnitude for each participant varied among repeated trials, and the averaging of multiple trials was helpful in establishing the individual response. This technique shows good potential for the clinical investigation of vascular autoregulation.

Optical Coherence Tomography Angiography of the Peripapillary Retina in Glaucoma.

Vascular factors may have important roles in the pathophysiology of glaucoma. A practical method for the clinical evaluation of ocular perfusion is needed to improve glaucoma management. To detect peripapillary retinal perfusion in glaucomatous eyes compared with normal eyes using optical coherence tomography (OCT) angiography. Prospective observational study performed from July 24, 2013, to April 17, 2014. Participants were recruited and tested at Casey Eye Institute, Oregon Health & Science University. In total, 12 glaucomatous eyes and 12 age-matched normal eyes were analyzed. The optic disc region was imaged twice using a 3 × 3-mm scan by a 70-kHz, 840-nm-wavelength spectral OCT system. The split-spectrum amplitude-decorrelation angiography algorithm was used. Peripapillary flow index was calculated as the mean decorrelation value in the peripapillary region, defined as a 700-µm-wide elliptical annulus around the disc. Peripapillary vessel density was the percentage area occupied by vessels. The data statistical analysis was performed from October 30, 2013, to May 30, 2014. Variability was assessed by the coefficient of variation. The Mann-Whitney test was used to compare the 2 groups of eyes. Correlations between vascular and visual field variables were assessed by linear regression analysis. In 12 normal eyes, a dense microvascular network around the disc was visible on OCT angiography. In 12 glaucomatous eyes, this network was visibly attenuated globally and focally. In normal eyes, between-visit reproducibilities of peripapillary flow index and peripapillary vessel density were 4.3% and 2.7% of the coefficient of variation, respectively, while the population variabilities of peripapillary flow index and peripapillary vessel density were 8.2% and 3.0% of the coefficient of variation, respectively. Peripapillary flow index and peripapillary vessel density in glaucomatous eyes were lower than those in normal eyes (P < .001 for both). Peripapillary flow index (Pearson r = -0.808) and peripapillary vessel density (Pearson r = -0.835) were highly correlated with visual field pattern standard deviation in glaucomatous eyes (P = .001 for both). The areas under the receiver operating characteristic curve for normal vs glaucomatous eyes were 0.892 for peripapillary flow index and 0.938 for peripapillary vessel density. Using OCT angiography, reduced peripapillary retinal perfusion in glaucomatous eyes can be visualized as focal defects and quantified as peripapillary flow index and peripapillary vessel density, with high repeatability and reproducibility. Quantitative OCT angiography may have value in future studies to determine its potential usefulness in glaucoma evaluation.

Choroidal Thickness in Turkish Children with Anisometric Amblyopia

Purpose: To assess macular choroidal thickness (CT) and axial length measurements in children with anisometropic amblyopia and to compare the measurements with that of fellow non-amblyopic eyes and age-sex matched controls. Methods: Forty patients with anisometropic amblyopia and 40 age-/sex-matched controls were evaluated in this study. Eyes were classified into three groups as follows: amblyopic eyes (n = 40), fellow non-amblyopic eyes, and healthy eyes (n = 40). All subjects underwent complete ophthalmic examination and macular choroidal thickness measurements by enhanced depth imaging method of the Spectralis optical coherence tomography system. CT was measured at the fovea and at 1000-μm intervals from the foveal center in both temporal and nasal directions. The statistical assessment was performed with the assistance of one-way analysis of variance (ANOVA) and Pearson’s correlation test. Results: The mean subfoveal CT was 389.35, 349.07, and 315.8 μm in the amblyopic, fellow non-amblyopic and healthy eyes, respectively. Choroid was thickest in subfoveal and thinnest in nasal regions among all groups. Both amblyopic and fellow non-amblopic eyes were more hyperopic than healthy eyes. While the subfoveal and nasal CT in amblyopic eyes and fellow eyes were significantly higher than healthy eyes, the temporal CT in amblyopic eyes was significantly higher than in healthy eyes. There was a significant positive correlation between the CT of the subfoveal, nasal, and temporal regions and the refractive state (r = 0.432 p = 0.001; r = 0.324 p = 0.001; r = 0.215 p = 0.01, respectively). Conclusion: The macular choroidal thickness—not only in amblyopic eyes but also in non-amblyopic fellow eyes—was significantly thicker than in the healthy subjects. The thick choroid in amblyopic and non-amblyopic fellow eyes may indicate bilateral delay of emmetropization, which probably means amblyopia affecting the visual feedback of both eyes.

Optimization of the split-spectrum amplitude-decorrelation angiography algorithm on a spectral optical coherence tomography system.

The split-spectrum amplitude-decorrelation angiography algorithm was optimized on a spectral optical coherence tomography system using a flow phantom. The number of times the spectrum was split and the bandwidth of each split were adjusted to maximize the flow phantom decorrelation signal-to-noise ratio. The improvement in flow detection was then demonstrated with en face retinal angiograms. The optimized algorithm increased the detectable retinal microvascular flow and decreased the variability of the quantified vessel density in OCT retinal angiograms of healthy human subjects.

Sine-modulated wavelength-independent full-range complex spectral optical coherence tomography with an ultra-broadband light source

We present a full-range complex spectral domain optical coherence tomography with an ultra-broadband light source based on sinusoidal modulation. For the sinusoidal modulation strategy, a lead zirconate titanate stack actuator is employed to achieve the sinusoidal vibration of a mirror and therefore to get a series of spectral interferogram with different phase delays. The purpose of this strategy is to get higher performance complex-conjugate artifact elimination. Bessel separation of the signal sequence at each wavelength of the spectrometer was used to reconstruct the real and imaginary components of interference fringes; however, the sinusoidal modulation method is independent of light source wavelength. The experimental results demonstrated that the method had an excellent performance in a complex-conjugate suppression of 50 dB for a full width at half maximum bandwidth of 236 nm, and it has better anti-artifact ability and more flexible range in phase shifting than the conventional wavelength-dependent phase-shifting method on a full-range complex spectral optical coherence tomography system. Furthermore, the effect of the hysteresis error of lead zirconate titanate actuators on the performance of complex-conjugate artifact elimination was investigated and the solution of lead zirconate titanate positioning performance for both conventional phase-shifting and sine-modulation methods was suggested.

Macular choroidal thickness measurements in patients with obstructive sleep apnea syndrome.

The purpose of this study is to assess macular choroidal thickness measurements in patients with different severities of obstructive sleep apnea syndrome (OSAS) versus normal controls by using enhanced depth imaging optical coherence tomography (EDI-OCT). This paper is a descriptive study. In this prospective study, the macular area of 74 patients with OSAS and 33 controls were evaluated. All subjects underwent complete ophthalmic examination and macular choroidal thickness (CT) measurements by enhanced depth imaging method of the Spectralis optical coherence tomography system. Choroidal thickness (CT) was measured at the fovea and at 1,000-μm intervals from the foveal center in both temporal and nasal directions by two masked observers. The mean age was not significantly different between patients with OSAS and controls. Patients were grouped as mild (n = 15), moderate (n = 28), and severe (n = 31) according to apnea-hypopnea index (AHI) scores. The mean subfoveal choroidal thickness (SFCT) was 338.0 ± 85.2μm in the control group versus 351.3 ± 90, 307.8 ± 65.5, and 325.4 ± 110.2μm in mild, moderate, and severe groups, respectively (p = 0.416). There was no significant correlation between the severity of OSAS and choroidal thickness. The patients with OSAS seem to protect the choroidal thickness despite hypoxia. The role of OSAS in the pathophysiology of choroidal blood flow and choroidal structure needs further investigation.

Retinal Layer Segmentation in Patients with Multiple Sclerosis Using Spectral Domain Optical Coherence Tomography

To evaluate the thickness of the 10 retinal layers in the paramacular area of patients with multiple sclerosis (MS) compared with healthy subjects using the new segmentation technology of spectral domain optical coherence tomography (OCT). To examine which layer has better sensitivity for detecting neurodegeneration in patients with MS. Observational, cross-sectional study. Patients with MS (n = 204) and age-matched healthy subjects (n = 138). The Spectralis OCT system (Heidelberg Engineering, Inc., Heidelberg, Germany) was used to obtain automated segmentation of all retinal layers in a parafoveal scan in 1 randomly selected eye of each participant, using the new segmentation application prototype. The thicknesses of 512 parafoveal points in the 10 retinal layers were obtained in each eye, and the mean thickness of each layer was calculated and compared between patients with MS and healthy subjects. The analysis was repeated, comparing patients with MS with and without previous optic neuritis. Correlation analysis was performed to evaluate the association between each retinal layer mean thickness, duration of disease, and functional disability in patients with MS. A logistic regression analysis was performed to determine which layer provided better sensitivity for detecting neurodegeneration in patients with MS. All retinal layers, except the inner limiting membrane, were thinner in patients with MS compared with healthy subjects (P < 0.05). Greater effects were observed in the inner retinal layers (nerve fiber, ganglion cells, inner plexiform, and inner nuclear layers) of eyes with previous optic neuritis (P < 0.05). The retinal nerve fiber layer and ganglion cell layer thicknesses were inversely correlated with the functional disability score in patients with MS. The ganglion cell layer and inner plexiform layer thicknesses could predict axonal damage in patients with MS. Analysis based on the segmentation technology of the Spectralis OCT revealed retinal layer atrophy in patients with MS, especially of the inner layers. Reduction of the ganglion cell and inner plexiform layers predicted greater axonal damage in patients with MS.

Distribution of Retinal Layer Atrophy in Patients With Parkinson Disease and Association With Disease Severity and Duration

To evaluate the thickness of the 10 retinal layers in the paramacular area of Parkinson disease patients using a new segmentation technology of optical coherence tomography (OCT) to examine whether the thickness of specific layers predicts neurodegeneration or Parkinson disease severity. Observational prospective study. Parkinson disease patients (n = 129) and age-matched healthy subjects (n = 129) were enrolled. The Spectralis OCT system was used to automatically segment all retinal layers in a parafoveal scan using the new segmentation application prototype. Mean thickness of each layer was calculated and compared between Parkinson disease patients and healthy subjects, and between Parkinson disease patients with disease durations of less than or at least 10 years. A correlation analysis was performed to evaluate the association between retinal layer thickness, duration of disease, and Parkinson disease severity. Logistic regression analysis was performed to determine the most sensitive layer for predicting axonal atrophy. Parkinson disease patients showed statistically significant reduced thickness in the retinal nerve fiber, ganglion cell, inner plexiform, and outer plexiform layers and increased thickness in the inner nuclear layer compared with healthy subjects (P < .05). The inner retinal layers were more affected in Parkinson disease patients with long disease duration. The ganglion cell layer thickness was inversely correlated with disease duration and Parkinson disease severity, and was predictive of axonal damage in Parkinson disease patients. The segmentation application of the Spectralis OCT revealed retinal layer atrophy in Parkinson disease patients, especially in the inner layers of patients with long disease duration. Ganglion cell layer reduction was associated with increased axonal damage.

Enhanced Depth Imaging Optical Coherence Tomography of the Choroid in Central Retinal Vein Occlusion

To evaluate subfoveal choroidal thickness in patients with central retinal vein occlusion (CRVO) using enhanced depth imaging optical coherence tomography. Retrospective observational study. We measured bilateral subfoveal choroidal thickness, averaged for 100 scans, in 36 patients (mean age, 66 ± 15 years; 26 women and 10 men) with unilateral CRVO by using the enhanced depth imaging methods of the Spectralis optical coherence tomography system. Twenty-two patients were treated with intravitreal bevacizumab (1.25 mg/0.05 mL), and subfoveal choroidal thickness was measured before and after treatment. Statistical analysis was performed to compare subfoveal choroidal thickness of CRVO and fellow eyes and to compare subfoveal choroidal thickness before and after intravitreal bevacizumab. Mean subfoveal choroidal thickness measured in 36 eligible eyes of 36 patients was 257.1 ± 83.2 μm, which was significantly greater than that in fellow eyes (222.6 ± 67.8 μm; P < .01, paired t test). There was strong correlation between CRVO eyes and fellow eyes (r = 0.79, P < .01). Mean subfoveal choroidal thickness after intravitreal bevacizumab was 227.7 ± 65.1 μm, which was significantly thinner than that before intravitreal bevacizumab therapy (266.9 ± 79.0 μm; P < .01, paired t test). Subfoveal choroidal thickness of CRVO eyes was significantly greater than that of fellow eyes and decreased significantly after intravitreal bevacizumab treatment. Enhanced depth imaging optical coherence tomography can be used to evaluate choroidal involvement in CRVO and may assist noninvasive diagnosis and management of this disease.

Neural networks to identify multiple sclerosis with optical coherence tomography

To compare axonal loss in ganglion cells detected with spectral-domain optical coherence tomography (OCT) in eyes of patients with multiple sclerosis (MS) versus healthy control subjects using an artificial neural network (ANN). To analyse the capability of the ANN technique to improve the detection of retinal nerve fibre layer (RNFL) damage in patients with multiple sclerosis. Patients with multiple sclerosis (n = 106) and age-matched healthy subjects (n = 115) were enrolled. The Spectralis OCT system was used to obtain the circumpapillary RNFL thickness in both eyes. The 768 RNFL thickness measurements provided by the Spectralis OCT were performed to obtain thickness measurements from 24 uniformly divided locations around the peripapillary RNFL. The performance of the ANN technique for identifying RNFL loss in patients with multiple sclerosis was evaluated. Receiver-operating characteristic (ROC) curves were used to display the ability of the test to discriminate between MS and healthy eyes in our population. ROC curves obtained using ANN and parameters provided by OCT (mean and 6 sector thicknesses) were compared. The capability of the ANN technique to detect RNFL loss in patients with multiple sclerosis compared with healthy subjects was good. The area under the ROC curve was 0.945. Compared with the OCT-provided parameters, the ANN had the largest area under the ROC curve. Measurements of RNFL thickness obtained with Spectralis OCT have a good ability to differentiate between healthy and individuals with multiple sclerosis. Based on the area under the ROC curve, the ANN performed better than any single OCT parameter.

Three-Dimensional Geometries Representing the Retinal Nerve Fiber Layer in Multiple Sclerosis, Optic Neuritis, and Healthy Eyes

Background: To represent and interpret the three-dimensional (3D) geometry and the distribution of the axonal damage to the retinal nerve fiber layer (RNFL) in patients with multiple sclerosis (MS) compared with healthy subjects. To analyze alterations in RNFL morphology in eyes of MS patients with or without previous episodes of optic neuritis (ON). Methods: MS patients (n = 122) and age-matched healthy subjects (n = 108) were enrolled. The Spectralis optical coherence tomography system was used to determine the circumpapillary RNFL thickness. The 768 RNFL thickness measurements were used to evaluate thickness measurements in patients with or without antecedent ON and to design a 3D reconstruction of the RNFL thickness representing the mechanobiologic tissue response to neurodegeneration caused by MS and ON episodes. Results: RNFL thickness was decreased in MS patients, and was higher in the MS group with previous ON. Statistical analysis and 3D RNFL reconstruction revealed greater damage to the ganglionar cells in the superonasal RNFL area (101.77 µm in MS vs. 125.47 µm in healthy subjects) and in the inferotemporal RNFL (119.05 µm in MS eyes and 149.26 µm in healthy eyes). Conclusions: The 3D representation of RNFL thickness based on measurements allows physicians to better observe damage in the temporal areas, especially in patients with previous ON.

Diagnostic Capability of Lamina Cribrosa Thickness by Enhanced Depth Imaging and Factors Affecting Thickness in Patients with Glaucoma

To determine the diagnostic ability of laminar thickness obtained using enhanced depth imaging (EDI) of the Heidelberg Spectralis optical coherence tomography (OCT) system (Heidelberg Engineering, Heidelberg, Germany) and the factors related to laminar thickness in patients with glaucoma. Evaluation of a diagnostic test. A total of 144 patients with glaucoma (68 with primary open-angle glaucoma [POAG], 76 with normal-tension glaucoma [NTG]), and 65 healthy controls. All patients underwent retinal nerve fiber layer (RNFL) thickness and optic nerve head (ONH) scanning with the Spectralis OCT system. Mean laminar thickness was defined at the center of the mid-superior, central, and mid-inferior horizontal B-scans of the ONH, and the mean of 3 laminar thickness measurements was used for the diagnostic test. Receiver operating characteristic (ROC) curves were obtained for average and quadrant RNFL thickness and mean laminar thickness. Areas under the ROC curve (AUCs), 95% confidence intervals (CIs), and sensitivities at a fixed specificity (90%) were calculated. Factors related to mean laminar thickness were analyzed by univariate and multivariate regression analyses in patients with glaucoma. Comparison of diagnostic ability using AUCs. Mean laminar thickness had the largest AUCs among all patients with glaucoma (AUC, 0.980; 95% CI, 0.966-0.993) and patients with NTG (AUC, 0.989; 95% CI, 0.980-0.994). The AUC of the mean laminar thickness of patients with NTG was significantly different from the AUC of the inferior RNFL thickness (AUC, 0.947; 95% CI, 0.929-0.965; P = 0.047), which had the largest AUC among the RNFL thickness parameters. The AUCs for discrimination between early glaucomatous eyes and normal eyes showed significant differences between the NTG group (AUC, 0.981; 95% CI, 0.968-0.992) and all patients with glaucoma (AUC, 0.941; 95% CI, 0.931-0.952; P = 0.007). The factor significantly associated with laminar thickness in both univariate and multivariate regression was NTG diagnosis (P = 0.001). The diagnostic ability of laminar thickness was comparable to that of peripapillary RNFL thickness in patients with glaucoma overall and better than peripapillary RNFL thickness in patients with early NTG.

Automated segmentation of retinal blood vessels in spectral domain optical coherence tomography scans

The correct segmentation of blood vessels in optical coherence tomography (OCT) images may be an important requirement for the analysis of intra-retinal layer thickness in human retinal diseases. We developed a shape model based procedure for the automatic segmentation of retinal blood vessels in spectral domain (SD)-OCT scans acquired with the Spectralis OCT system. The segmentation procedure is based on a statistical shape model that has been created through manual segmentation of vessels in a training phase. The actual segmentation procedure is performed after the approximate vessel position has been defined by a shadowgraph that assigns the lateral vessel positions. The active shape model method is subsequently used to segment blood vessel contours in axial direction. The automated segmentation results were validated against the manual segmentation of the same vessels by three expert readers. Manual and automated segmentations of 168 blood vessels from 34 B-scans were analyzed with respect to the deviations in the mean Euclidean distance and surface area. The mean Euclidean distance between the automatically and manually segmented contours (on average 4.0 pixels respectively 20 µm against all three experts) was within the range of the manually marked contours among the three readers (approximately 3.8 pixels respectively 18 µm for all experts). The area deviations between the automated and manual segmentation also lie within the range of the area deviations among the 3 clinical experts. Intra reader variability for the experts was between 0.9 and 0.94. We conclude that the automated segmentation approach is able to segment blood vessels with comparable accuracy as expert readers and will provide a useful tool in vessel analysis of whole C-scans, and in particular in multicenter trials.