Quantitative analysis of the intraretinal layers and optic nerve head using ultra-high resolution optical coherence tomography

Analysis of the capsular bend in posterior capsular opacification using anterior segment optical coherence tomography

PURPOSE

To investigate the link between the capsular bend and the morphological types and characteristics of posterior capsular opacification (PCO) using anterior segment optical coherence tomography.

METHODS

Thirty eyes with PCO were examined, and three types of PCO were identified: pearl, fibrosis, and mixed. We assessed anterior capsular overlap, intraocular lens-capsule adhesion, and capsular bending. In addition to measuring the intraocular lens-posterior capsule distance and capsule bending angle (CBA), the PCO parameters (area, density, and score at 6-, 5-, and 3-mm intraocular lens optic regions) were recorded. The associations between capsular bend and PCO type and characteristics were investigated. A control group of 12 eyes without PCO was used to compare the study variables.

RESULTS

With p values greater than 0.001, there was a statistically significant difference in the mean PCO area and score at the 6-, 5-, and 3-mm optic zones in different PCO types, with the pearl type having the highest value, followed by the mixed type, and finally the fibrosis type. The PCO group had a significantly higher mean CBA than the control group (P = 0.001). CBA was positively related to intraocular lens-posterior capsule distance, PCO area, and PCO score at the 6-, 5-, and 3-mm zones (P = 0.001). The receiver operating characteristic curve's cut-off point for CBA was 96.85° when comparing PCO cases to controls. Partial overlap and incomplete adhesion were statistically more common in the PCO eyes than in the control (P = 0.001, 0.003, respectively).

CONCLUSION

PCO types and CBA have a strong relationship with PCO score and intraocular lens-posterior capsule space. In PCO's eyes, CBA has a cut-off value of 96.85°.

Foveal pit morphological changes in asymptomatic carriers of the G11778A mutation with Leber's hereditary optic neuropathy

AIM

To investigate the foveal pit morphology changes in unaffected carriers and affected Leber's hereditary optic neuropathy (LHON) patients with the G11778A mutation from one family.

METHODS

This study was a prospective cross-sectional study. Both eyes from 16 family members (age from 9 to 47y) with the G11778A mutation were analyzed and compared with 1 eye from 20 normal control subjects. Eleven family members with the G11778A mutation but without optic neuropathy were classified as unaffected carriers (n=22 eyes). Five family members (n=10 eyes) expressed the LHON phenotype and were classified as affected patients. Retinal images of all the subjects were taken by optical coherence tomography (OCT), and an automatic algorithm was used to segment the retina to eight layers. Horizontal and vertical OCT images centered on the fovea were used to measure intra-retinal layer thicknesses and foveal morphometry.

RESULTS

Thicker foveal thickness, thinner foveal pit depth, and flatter foveal slopes were observed in unaffected carriers and affected LHON patients (all P<0.001). Further, the slopes of all four sectors in the LHON were flatter than those in the unaffected carriers (all P<0.001). Compared with the control group, affected LHON patients had a thinner retinal nerve fiber layer (RNFL), ganglion cell layer and inner plexiform layer (GCL+IPL), and total retina (all P<0.01). The retinal nerve fiber layer (RNFL) of affected patients was 38.0% thinner than that of controls while the GCL+IPL was 40.1% thinner.

CONCLUSION

The foveal pit morphology shows changes in both unaffected carriers and affects patients. RNFL and GCL+IPL are thinner in affected LHON patients but not in unaffected carriers.

Thickness of individual layers at the macula and associated factors: the Beijing Eye Study 2011

BACKGROUND

Diagnosis and follow-up of retinal diseases may be improved if the thickness of the various retinal layers, in addition to the total retinal thickness, is taken into account. Here we measured the thickness of the macular retinal layers in a population-based study group to assess the normative values and their associations.

METHODS

Using spectral-domain optical coherence tomographic images (Spectralis®, wavelength: 870 nm; Heidelberg Engineering Co, Heidelberg, Germany), we measured the thickness of the macular retinal layers in participants of the population-based Beijing Eye Study without ocular diseases and without systematic diseases, such as arterial hypertension, hyperlipidemia, diabetes mellitus, cardiovascular diseases, previous myocardial infarction, cerebral trauma and stroke. Segmentation and measurement of the retinal layers was performed automatically in each of the horizontal scans.

RESULTS

The study included 384 subjects (mean age:60.0 ± 8.0 years). The mean thickness of the whole retina, outer plexiform layer, outer nuclear layer,retinal pigment epithelium, inner retinal layer and photoreceptor layer was 259.8 ± 18.9 μm, 19.4 ± 3.9 μm, 93.4 ± 9.6 μm, 17.6 ± 1.9 μm, 169.8 ± 18.6 μm, and 90.0 ± 4.2 μm, respectively. In multivariable analysis, the thickness of the foveola and of all retinal layers in the foveal, parafoveal and perifoveal region decreased with older age (all P < 0.05), except for the thickness of the parafoveal outer plexiform layer which increased with age. Men as compared to women had higher thickness measurements of the photoreceptor layer and outer nuclear layer in all areas, and of all layers between the retinal nerve fiber layer and inner nuclear layer in the parafoveal area (all P < 0.05). The associations between the macular retinal layers thickness and axial length were not consistent. The inner plexiform layer was thicker, and the ganglion cell layer and inner nuclear layer were thinner, in the temporal areas than in the nasal areas, CONCLUSIONS: The associations between decreasing thickness of most retinal layers with older age and the correlation of a higher thickness of some retinal layers with male gender may clinically be taken into account.

Visualization of Focal Thinning of the Ganglion Cell-Inner Plexiform Layer in Patients with Mild Cognitive Impairment and Alzheimer's Disease

BACKGROUND

A detailed analysis of the tomographic thickness of intraretinal layers may provide more information on neurodegeneration in patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD).

OBJECTIVE

The goal was to analyze tomographic thickness patterns of intraretinal layers in patients with AD andMCI.

METHOD

Forty-nine patients (25 AD and 24 MCI) and 21 cognitively normal (CN) controls were imaged using ultra-high-resolution optical coherence tomography to obtain volumetric data centered on the fovea. The segmented intraretinal layers were retinal nerve fiber layer (RNFL), ganglion cell- inner plexiform layer (GCIPL), inner nuclear layer (INL), outer nuclear layer (ONL), outer plexiform layer (OPL), and retinal photoreceptor (PR), in addition to the total retinal thickness(TRT).

RESULTS

The thickness differences were negative (thinning) mainly in TRT, RNFL, and GCIPL in both AD and MCI groups in comparison to CN, while the thickness differences were positive (thickening) mainly in ONL and PR in AD. GCIPL of AD and MCI was thinner in superior, nasal superior, and temporal superior quadrants, compared to CN (p < 0.05). GCIPL of the inner superior, inner nasal superior, inner temporal superior, and outer nasal superior sectors was significantly thinner in AD than CN (p < 0.05). GCIPL of the outer superior, inner temporal superior, outer nasal, and temporal superior sectors was significantly thinner in MCI than CN (p < 0.05).

CONCLUSION

Focal thinning of the GCIPL was visualized and quantified by detailed partitions in AD and MCI, which provides specific information about neurodegeneration in MCI and AD.

Retinal structural-vascular-functional relationship using optical coherence tomography and optical coherence tomography - angiography in myopia

Background

To examine the retinal structure–vascular-function relationship using optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) in myopia.

Methods

This was a prospective cross-sectional study comprising 86 eyes of 45 individuals with varying axial lengths and spherical equivalents and no posterior segment abnormalities. All eyes underwent optical coherence tomography with the Spectralis SD-OCT and OCTA with RTVue-XR Avanti; Optovue. Individual macular retinal layer thicknesses and flow areas and vessel densities were measured on OCT and OCTA, respectively. Linear correlations were made between the macular layer thicknesses, flow areas and vessel densities with axial length, spherical equivalent and visual acuity.

Results

The participants’ mean ages were 33.34 ± 14.45 years, mean spherical equivalent refractions were − 7.17 ± 5.71 D and axial lengths were 25.95 ± 2.41 mm. There were significant positive correlations of foveal angle (r = 0.757, p = 0.001), inner retinal (r = 0.764, p = 0.001) and outer plexiform layer (r = 0.771, p = 0.001) thickness on OCT and vessel densities in deep capillary plexus (r = 0.313, p = 0.003) on OCTA with axial length and negative correlations with spherical equivalents and visual acuity. Significant negative correlations of outer nuclear layer (r = − 0.560, p = 0.03) and photoreceptor outer segment layer thickness (r = − 0.856, p < 0.001) were noted on OCT with axial length and positive correlations with spherical equivalents and visual acuity.

Conclusion

The lateral retinal stretching in myopia could possibly explain the correlation between retinal layer thickness, vascular density and visual acuity in these eyes. Further research is required to investigate this.

Ultra-high resolution profiles of macular intra-retinal layer thicknesses and associations with visual field defects in primary open angle glaucoma

The structural characteristics of the outer retinal layers in primary open angle glaucoma (POAG) are still controversial, and these changes, along with those in the inner retinal layers, could have clinical and/or pathophysiological significance. A custom-built ultra-high resolution optical coherence tomography (UHR-OCT) combined with an automated segmentation algorithm can image and measure the eight intra-retinal layers. The purpose of this study is to determine the thickness characteristics of the macular intra-retinal layers, especially the outer layers, in POAG patients. Thirty-four POAG patients (56 eyes) and 33 normal subjects (63 eyes) were enrolled. Thickness profiles of the eight intra-retinal layers along a 6-mm length centred on the fovea at the horizontal and vertical meridians were obtained and the regional thicknesses were compared between two groups. The associations between the thicknesses of each intra-retinal layer and the macular visual field (VF) sensitivity were then analysed. POAG affected not only the inner retinal layers but also the photoreceptor layers and retinal pigment epithelium of the outer retina. However, the VF loss was correlated mainly with the damage of the inner retinal layers. UHR-OCT with automated algorithm is a useful tool in detecting microstructural changes of macula with respect to the progression of glaucoma.

The measurement repeatability using different partition methods of intraretinal tomographic thickness maps in healthy human subjects

Purpose

To determine the repeatability and profiles with different partition methods in intraretinal thickness layers in healthy human subjects, using optical coherence tomography (OCT).

Methods

A custom-built ultrahigh-resolution OCT was used to acquire three-dimensional volume of the macula in 20 healthy subjects. The dataset was acquired twice using the macular cube 512×128 protocol in an area of 6×6 mm² centered on the fovea. Commercially available segmentation software (Orion™) was used to segment the dataset into thickness maps of six intraretinal layers. The coefficient of repeatability and intraclass coefficient of correlation (ICC) were analyzed using hemispheric zoning and sectors defined by the Early Treatment Diabetic Retinopathy Study (ETDRS).

Results

All datasets were successfully segmented to create six thickness maps of individual intraretinal layers. Coefficients of repeatabilities of these layers in hemispheric zones ranged from 0.9 to 6.6 µm, with an average of 3.6 µm (standard deviation [SD] 1.4), which was not significantly different compared to ETDRS sectors (P>0.05). ICCs of these layers in hemispheric zones ranged from 0.68 to 0.99, with an average of 0.91 (SD 0.07). There were no significant differences in ICCs between two zoning methods (P>0.05). Significant variations of tomographic intraretinal thicknesses were found between the inner and outer annuli and among the quadrantal sectors within the inner and outer annuli (P<0.05). Significant variations of the quadrantal sectors including both inner and outer annuli were evident in intraretinal layers (P<0.05) except for the outer plexiform layer.

Conclusion

The measurement repeatabilities of tomographic thicknesses of intraretinal layers are comparable using both hemispheric and ETDRS partitions in volumetric data combined with the commercially available segmentation software. In keeping with known, normal anatomical variation, significant differences in tomographic thickness in various intraretinal layers were apparent in both hemispheric and ETDRS sectors.

In vivo imaging of retinal hemodynamics with OCT angiography and Doppler OCT

Retinal hemodynamics is important for early diagnosis and precise monitoring in retinal vascular diseases. We propose a novel method for measuring absolute retinal blood flow in vivo using the combined techniques of optical coherence tomography (OCT) angiography and Doppler OCT. Doppler values can be corrected by Doppler angles extracted from OCT angiography images. A three-dimensional (3D) segmentation algorithm based on dynamic programming was developed to extract the 3D boundaries of optic disc vessels, and Doppler angles were calculated from 3D vessel geometry. The accuracy of blood flow from the Doppler OCT was validated using a flow phantom. The feasibility of the method was tested on a subject in vivo. The pulsatile retinal blood flow and the parameters for retinal hemodynamics were successfully obtained.

Automatic segmentation of the optic nerve head for deformation measurements in video rate optical coherence tomography

Optical coherence tomography (OCT) imaging has become a standard diagnostic tool in ophthalmology, providing essential information associated with various eye diseases. In order to investigate the dynamics of the ocular fundus, we present a simple and accurate automated algorithm to segment the inner limiting membrane in video-rate optic nerve head spectral domain (SD) OCT images. The method is based on morphological operations including a two-step contrast enhancement technique, proving to be very robust when dealing with low signal-to-noise ratio images and pathological eyes. An analysis algorithm was also developed to measure neuroretinal tissue deformation from the segmented retinal profiles. The performance of the algorithm is demonstrated, and deformation results are presented for healthy and glaucomatous eyes.

Macular Thickness Profiles of Intraretinal Layers in Myopia Evaluated by Ultrahigh-Resolution Optical Coherence Tomography

PURPOSE

To investigate the thickness and variation profiles of 8 intraretinal layers in myopia.

DESIGN

Prospective cross-sectional study.

METHODS

Young subjects with spherical equivalents ranging from +0.50 to -10.25 diopters and good corrected vision were divided into emmetropic (n = 20), low myopic (n = 50), and high myopic (n = 30) groups. Retinal images centered on the fovea along the horizontal and vertical meridians were obtained by ultrahigh-resolution optical coherence tomography (OCT). Macular images were segmented into 8 intraretinal layers by an automatic segmentation algorithm to yield thickness profiles within a 6-mm-diameter circle divided into central, pericentral, and peripheral regions.

RESULTS

For intraretinal layers in the central region, the outer segment of receptors layer was thicker in the high myopic group and positively correlated with axial length. In the pericentral and peripheral regions, all layers except the ganglion cell and inner plexiform layer had thickness changes in high myopia. The total thickness of the peripheral region was less than in the emmetropic controls owing to thinner inner nuclear layer, combined Henle fiber and outer nuclear layer, and outer segment of receptors layer. Nevertheless, the thicknesses of the combined myoid and ellipsoid zone and the combined interdigitation zone and retinal pigment epithelium/Bruch complex in the peripheral region were greater than for the emmetropic controls.

CONCLUSIONS

Intraretinal layer thicknesses in young high myopic eyes varied significantly from emmetropic controls, especially in the peripheral region. Ultrahigh-resolution OCT with automated segmentation can detect changes in retinal macular microstructure during the development of myopia.

Do different spectral domain OCT hardwares measure the same? Comparison of retinal thickness using third-party software

PURPOSE

Spectral-domain optical coherence tomographies (OCTs) from different companies do not give identical retinal thicknesses. The purpose of this study was to evaluate if differences in thickness when using a spectral domain Cirrus OCT or a Heidelberg Spectralis are due to hardware differences, or if they are caused by the segmentation algorithms.

METHODS

Thirty-seven healthy eyes were examined within the same session with a Cirrus OCT and a Spectralis OCT, the latter using averaged B-scans. Scans from similar positions and passing the fovea were analyzed by custom-made software. Thickness was analyzed at the fovea, the central 1-mm line and the 6-mm line.

RESULTS

When Cirrus and Spectralis scans were analyzed with the same software, the retinal thickness at the foveal center was 225.92 μm (SD 17.0) using the Cirrus and 228.70 μm (SD 18.4) using the Spectralis; the difference of 2.78 μm was not significant (p = 0.055). For the central 1 mm, the difference was 1.78 μm (p = 0.0414), and for all points out to 6 mm, the Spectralis retinal thickness was also significantly larger than the Cirrus thickness (p = 0.0052), though the mean difference was only 1.85 μm. Also for the RPE_OScomplex, Spectralis measured a greater thickness than did Cirrus, with a mean of 3.32 μm (p < 0.0001) for all points.

CONCLUSION

The retinal thicknesses from the Cirrus and from the Spectralis differed by 14 μm with the standard software of the instruments, and by less than 3 μm when analyzed with the same custom-made software, indicating that the major differences between the two SD-OCT systems are due to differences in their built-in software algorithms.

Optical coherence tomography for an in-vivo study of posterior-capsule-opacification types and their influence on the total-pulse energy required for Nd:YAG capsulotomy: a case series

Background

Posterior capsule opacification (PCO) is the most common post-operative complication associated with cataract surgery and is mostly treated with Nd:YAG laser capsulotomy. Here, we demonstrate the use of high-resolution spectral-domain optical coherence tomography (OCT) as a technique for PCO analysis. Additionally, we evaluate the influence of PCO types and the distance between the intraocular lens (IOL) and the posterior capsule (PC), i.e., the IOL/PC distance, on the total-pulse energy required for the Nd:YAG laser posterior capsulotomy.

Methods

47 eyes with PCO scheduled for the Nd:YAG procedure were examined and divided into four categories: fibrosis, pearl, mixed type and late-postoperative capsular bag distension syndrome. Using custom-made computer software for OCT image analysis, the IOL/PC distances in two dimensions were measured. The IOL/PC distances were compared with those of a control group of 15 eyes without PCO. The influence of the different PCO types and the IOL/PC distance on the total-pulse energy required for the Nd:YAG procedure was analyzed.

Results

The total-pulse energy required for a laser capsulotomy differs significantly between PCO types (p = 0.005, Kruskal-Wallis test). The highest energy was required for the fibrosis PCO type, followed by mixed, pearl and late-postoperative capsular bag distension syndrome. The IOL/PC distance also significantly influenced the total-pulse energy required for laser capsulotomy (p = 0.028, linear regression). Lower total-pulse energy was expected for a larger IOL/PC distance.

Conclusions

Our study indicates that the PCO types and the IOL/PC distance influence the total-pulse energy required for Nd:YAG capsulotomy. The presented OCT method has the potential to become an additional tool for PCO characterization. Our results are important for a better understanding of the photodisruptive mechanisms in Nd:YAG capsulotomy.

Fractal-based analysis of optical coherence tomography data to quantify retinal tissue damage

BACKGROUND

The sensitivity of Optical Coherence Tomography (OCT) images to identify retinal tissue morphology characterized by early neural loss from normal healthy eyes is tested by calculating structural information and fractal dimension. OCT data from 74 healthy eyes and 43 eyes with type 1 diabetes mellitus with mild diabetic retinopathy (MDR) on biomicroscopy was analyzed using a custom-built algorithm (OCTRIMA) to measure locally the intraretinal layer thickness. A power spectrum method was used to calculate the fractal dimension in intraretinal regions of interest identified in the images. ANOVA followed by Newman-Keuls post-hoc analyses were used to test for differences between pathological and normal groups. A modified p value of <0.001 was considered statistically significant. Receiver operating characteristic (ROC) curves were constructed to describe the ability of each parameter to discriminate between eyes of pathological patients and normal healthy eyes.

RESULTS

Fractal dimension was higher for all the layers (except the GCL + IPL and INL) in MDR eyes compared to normal healthy eyes. When comparing MDR with normal healthy eyes, the highest AUROC values estimated for the fractal dimension were observed for GCL + IPL and INL. The maximum discrimination value for fractal dimension of 0.96 (standard error =0.025) for the GCL + IPL complex was obtained at a FD ≤ 1.66 (cut off point, asymptotic 95% Confidence Interval: lower-upper bound = 0.905-1.002). Moreover, the highest AUROC values estimated for the thickness measurements were observed for the OPL, GCL + IPL and OS. Particularly, when comparing MDR eyes with control healthy eyes, we found that the fractal dimension of the GCL + IPL complex was significantly better at diagnosing early DR, compared to the standard thickness measurement.

CONCLUSIONS

Our results suggest that the GCL + IPL complex, OPL and OS are more susceptible to initial damage when comparing MDR with control healthy eyes. Fractal analysis provided a better sensitivity, offering a potential diagnostic predictor for detecting early neurodegeneration in the retina.

Repeatability and reproducibility of eight macular intra-retinal layer thicknesses determined by an automated segmentation algorithm using two SD-OCT instruments

Purpose

To evaluate the repeatability, reproducibility, and agreement of thickness profile measurements of eight intra-retinal layers determined by an automated algorithm applied to optical coherence tomography (OCT) images from two different instruments.

Methods

Twenty normal subjects (12 males, 8 females; 24 to 32 years old) were enrolled. Imaging was performed with a custom built ultra-high resolution OCT instrument (UHR-OCT, ∼3 µm resolution) and a commercial RTVue100 OCT (∼5 µm resolution) instrument. An automated algorithm was developed to segment the macular retina into eight layers and quantitate the thickness of each layer. The right eye of each subject was imaged two times by the first examiner using each instrument to assess intra-observer repeatability and once by the second examiner to assess inter-observer reproducibility. The intraclass correlation coefficient (ICC) and coefficients of repeatability and reproducibility (COR) were analyzed to evaluate the reliability.

Results

The ICCs for the intra-observer repeatability and inter-observer reproducibility of both SD-OCT instruments were greater than 0.945 for the total retina and all intra-retinal layers, except the photoreceptor inner segments, which ranged from 0.051 to 0.643, and the outer segments, which ranged from 0.709 to 0.959. The CORs were less than 6.73% for the total retina and all intra-retinal layers. The total retinal thickness measured by the UHR-OCT was significantly thinner than that measured by the RTVue100. However, the ICC for agreement of the thickness profiles between UHR-OCT and RTVue OCT were greater than 0.80 except for the inner segment and outer segment layers.

Conclusions

Thickness measurements of the intra-retinal layers determined by the automated algorithm are reliable when applied to images acquired by the UHR-OCT and RTVue100 instruments.