Swept-source Optical Coherence Tomography Scans Research Articles

The role of ultra-widefield imaging with navigated central and peripheral cross-sectional and three-dimensional swept source optical coherence tomography in ophthalmology: Clinical applications

Abstract: PURPOSE: To assess central and peripheral retinal and choroidal diseases using ultra-widefield (UWF) fundus imaging in combination with navigated central and peripheral cross-sectional and three-dimensional (3D) swept source optical coherence tomography (SS-OCT) scans. METHODS: Retrospective study involving 332 consecutive patients, with a nearly equal distribution of males and females. The mean age of patients was 52 years (range 18–92 years). Average refractive error was −3.80 D (range +7.75 to −20.75 D). RESULTS: The observations in this study demonstrate the efficacy of peripheral navigated SS-OCT in assessing various ocular conditions. The technology provides high-quality images of the peripheral vitreous, vitreoretinal interface, retina, and choroid, enabling visualization of vitreous floaters and opacities, retinal holes and tears, pigmented lesions, and peripheral retinal degenerations. 3D OCT scans enhance the visualization of these abnormalities and improve diagnostic and therapeutic decisions. CONCLUSION: Navigated central and peripheral cross-sectional and 3D SS-OCT scans offer significant complementary benefits in the assessment and management of retinal diseases. Their addition to UWF imaging provides a comprehensive view of central and peripheral ocular structures, aiding in early detection, precise anatomical measurements, and objective monitoring of disease progression. In addition, this technology serves as a valuable tool for patient education, a teaching tool for trainees, and documentation for medico-legal purposes.

Changes in Neurodegeneration and Visual Prognosis in Branch Retinal Vein Occlusion after Resolution of Macular Edema

This study aimed to examine the thicknesses of the ganglion cell layer (GCL) and peripapillary retinal nerve fiber layer (RNFL) in eyes with resolved macular edema (ME) in branch retinal vein occlusion (BRVO) and determine their relationship with visual acuity (VA). This retrospective observational case–control study included 57 eyes of BRVO patients with resolved ME after treatment. The macular GCL thickness, peripapillary RNFL thickness, and central macular thickness (CMT) measured on swept-source optical coherence tomography scans with the contralateral eyes used as controls were evaluated. The mean CMT was 270.48 ± 32.7 μm; the mean RNFL thickness was 105.46 ± 25.94 μm in BRVO eyes. Although the average RNFL thickness was decreased in BRVO eyes compared to unaffected eyes, there was no significant difference between the groups. However, the temporal and nasal RNFL thicknesses were significantly different between the groups. The mean affected quadrant had a significantly thinner GCL compared to the corresponding opposite unaffected quadrant (p = 0.02). Final VA was significantly correlated with nasal and middle GCL thicknesses in the affected area (r = −0.512, p = 0.003 and r = −0.537, p = 0.001, respectively); no correlation was found between the average RNFL thickness and mean CMT. The peripapillary RNFL and GCL thicknesses of the affected area were reduced in BRVO eyes compared to unaffected eyes. VA significantly correlated with nasal and middle GCL thicknesses in the affected area. Inner retinal damage occurring in patients with ME secondary to BRVO may be related to the visual prognosis.

Enhanced choroidal thickness, total choroidal area and choroidal vascularity index from deep‐learning generated OCT images

Aims/Purpose: Our goal is to enhance the visualization of the choroid in clinical standard spectral‐domain OCT (SDOCT) scans using a deep‐learning (DL) approach that uses matching swept‐source OCT (SSOCT). We aim to improve the measurement of the sub‐foveal choroidal thickness (SFCT), total choroidal area (TCA), and choroidal vascularity index (CVI) in SDOCT images.Methods: A total of 105 350 SDOCT and SSOCT B‐scan images (Zeiss Cirrus 5000 and Zeiss PlexElite) were used to develop the DL model. The data set included B‐scans from healthy (238 eye pairs from 155 patients) and glaucoma (192 eye pairs from 122 patients) subjects. The DL model learned deep anatomical features from SSOCT scans and generated enhanced SDOCT images. The peak signal‐to‐noise ratio (PSNR) and structural similarity index metric (SSIM) were used to assess the quality of generated images. In addition, we compared the anatomical parameters derived from the generated and ground‐truth SSOCT images, including SVCT, TCA and CVI values.Results: We tested our method using 20 580 B‐scan image pairs from 84 eyes. The DL‐generated images effectively preserved the anatomical structure of the retina layers and improved the visualization of the choroid. The enhanced SDOCT images had higher image quality than the original SDOCT images, as demonstrated by the higher PSNR (31 dB vs. 18 dB) and SSIM values (3.4 times higher SSIM than the original SDOCT images). SVCT, TCA, and CVI measurements from the DL‐generated SDOCT images showed strong correlations with corresponding measurements using SSOCT with high Pearson's coefficients (0.93, 0.99, and 0.93), high intra‐class correlation indices (0.96, 0.99 and 0.96), and high coefficient of determination r2 values (0.85, 0.98 and 0.86).Conclusions: Our DL model enhances the visibility of the choroid in images, surpassing the capabilities of standard clinical SDOCT images. As a result, accurate measurement of SVCT, TCA and CVI, which were previously limited due to imaging depth constraints of SDOCT, becomes possible. This technology opens up new possibilities for utilizing affordable SDOCT devices to study the choroid in healthy and pathological conditions.

Deep-learning-based automated measurement of outer retinal layer thickness for use in the assessment of age-related macular degeneration, applicable to both swept-source and spectral-domain OCT imaging.

Effective biomarkers are required for assessing the progression of age-related macular degeneration (AMD), a prevalent and progressive eye disease. This paper presents a deep learning-based automated algorithm, applicable to both swept-source OCT (SS-OCT) and spectral-domain OCT (SD-OCT) scans, for measuring outer retinal layer (ORL) thickness as a surrogate biomarker for outer retinal degeneration, e.g., photoreceptor disruption, to assess AMD progression. The algorithm was developed based on a modified TransUNet model with clinically annotated retinal features manifested in the progression of AMD. The algorithm demonstrates a high accuracy with an intersection of union (IoU) of 0.9698 in the testing dataset for segmenting ORL using both SS-OCT and SD-OCT datasets. The robustness and applicability of the algorithm are indicated by strong correlation (r = 0.9551, P < 0.0001 in the central-fovea 3 mm-circle, and r = 0.9442, P < 0.0001 in the 5 mm-circle) and agreement (the mean bias = 0.5440 um in the 3-mm circle, and 1.392 um in the 5-mm circle) of the ORL thickness measurements between SS-OCT and SD-OCT scans. Comparative analysis reveals significant differences (P < 0.0001) in ORL thickness among 80 normal eyes, 30 intermediate AMD eyes with reticular pseudodrusen, 49 intermediate AMD eyes with drusen, and 40 late AMD eyes with geographic atrophy, highlighting its potential as an independent biomarker for predicting AMD progression. The findings provide valuable insights into the ORL alterations associated with different stages of AMD and emphasize the potential of ORL thickness as a sensitive indicator of AMD severity and progression.

Quantitative analysis of choroidal alterations in thyroid eye disease using swept-source OCT

Purpose:To investigate choroidal alterations in patients with thyroid eye disease (TED) using swept-source optical coherence tomography (SS-OCT) and compare them with age-matched healthy controls.Methods:SS-OCT scans were performed to obtain quantitative measurements of choroidal parameters. Mean choroidal thickness (MCT), choroidal vessel volume (CVV), choroidal stroma volume (CSV), choroidal vascularity index (CVI), and choroidal stroma-to-vessel volume ratio (CSVR) were calculated and compared between TED and control eyes.Results:TED eyes exhibited significantly higher MCT (276.25 ± 58.75 μmvs. 236.86 ± 45.02 μm,p&amp;lt; 0.001), CVV (21.46 ± 5.10 mm3vs. 18.14 ± 3.83 mm3,p= 0.001), and CSV (13.86 ± 2.80 mm3vs. 11.44 ± 2.17 mm3,p&amp;lt; 0.001) compared to control eyes. However, there were no significant differences in CVI (0.61 ± 0.02vs. 0.61 ± 0.03,p= 0.838) or CSVR (0.65 ± 0.05vs. 0.64 ± 0.07,p= 0.345) between the two groups.Conclusion:SS-OCT effectively differentiated TED eyes from normal eyes based on choroidal alterations. The increased MCT, CVV, and CSV in TED suggest both dilated choroidal vasculature and expanded choroidal stroma. These findings highlight the potential of SS-OCT as an adjunctive imaging tool for the assessment of TED.

Optic Nerve Head Changes After Intraocular Pressure-Lowering Glaucoma Surgeries Using Optical Coherence Tomography.

Optic nerve head (ONH) changes were detected with swept-source optical coherence tomography (SS-OCT) after intraocular pressure (IOP)-lowering glaucoma surgeries. The aim of this study was to detect changes in the ONH with SS-OCT after IOP-lowering procedures. Patients with progressing glaucoma who were referred for IOP-lowering procedures were included. The participants underwent a 24-2 visual field test and SS-OCT (DRI OCT Triton Plus; Topcon). IOP and SS-OCT scans were obtained during the preoperative period and up to 7 days and 30-90 days postoperatively. ONH parameters were measured with a B -scan at the center of the optic disc and an average of 5 central B -scans. The hypotenuse of the ONH cup (HOC) was calculated using the Pythagorean theorem: hypotenuse 2 = leg1 2 + leg2 2 , considering the length and depth of the cup as the legs of a right triangle. We also evaluated changes in Bruch membrane opening (BMO)-to-BMO diameter. Statistical analysis was performed using generalized estimating equations. A total of 15 eyes were included. The mean patient age was 70 (SD, 11.04) years. The mean circumpapillary retinal nerve fiber layer was 60.13 (SD, 23.21) µm and the visual field mean deviation was -13.29 (SD, 8.5) dB. The mean IOP at each visit was: 20.5 (SD, 4.99); 11 (SD, 4.95), and 15.7 (SD, 5.04), respectively. The mean HOC, the mean depth and length of the ONH cup, and the BMO-to-BMO diameter decreased significantly after the IOP-lowering procedures. The HOC evaluated with SS-OCT significantly decreased after IOP-lowering surgeries. This parameter was useful for evaluating short-term changes in the ONH.

Automated segmentation and quantification of calcified drusen in 3D swept source OCT imaging.

Qualitative and quantitative assessments of calcified drusen are clinically important for determining the risk of disease progression in age-related macular degeneration (AMD). This paper reports the development of an automated algorithm to segment and quantify calcified drusen on swept-source optical coherence tomography (SS-OCT) images. The algorithm leverages the higher scattering property of calcified drusen compared with soft drusen. Calcified drusen have a higher optical attenuation coefficient (OAC), which results in a choroidal hypotransmission defect (hypoTD) below the calcified drusen. We show that it is possible to automatically segment calcified drusen from 3D SS-OCT scans by combining the OAC within drusen and the hypoTDs under drusen. We also propose a correction method for the segmentation of the retina pigment epithelium (RPE) overlying calcified drusen by automatically correcting the RPE by an amount of the OAC peak width along each A-line, leading to more accurate segmentation and quantification of drusen in general, and the calcified drusen in particular. A total of 29 eyes with nonexudative AMD and calcified drusen imaged with SS-OCT using the 6 × 6 mm2 scanning pattern were used in this study to test the performance of the proposed automated method. We demonstrated that the method achieved good agreement with the human expert graders in identifying the area of calcified drusen (Dice similarity coefficient: 68.27 ± 11.09%, correlation coefficient of the area measurements: r = 0.9422, the mean bias of the area measurements = 0.04781 mm2).

Morphologic Stages of Rhegmatogenous Retinal Detachment Assessed Using Swept-Source OCT

To describe the sequential morphologic changes after rhegmatogenous retinal detachment (RRD) utilizing a novel, objective, and clinically relevant staging system based on swept-source OCT (SS-OCT) and determine its association with the duration of fovea-off and postoperative visual acuity (VA). Prospective cohort study. Consecutive patients with primary fovea-involving RRD referred to St. Michael's Hospital, Toronto, Canada, from January 2020 to April2022. All patients underwent SS-OCT and ultrawide-field SS-OCT at baseline. Primary RRDs with breaks above the 8- and 4-o'clock meridians were included. Patients with vision loss for ≥ 3 months, proliferative vitreoretinopathy grade C or worse, a demarcation line, previous vitrectomy, or other retinal pathology were excluded. The staging was based on an assessment of outer retinal morphology on successive SS-OCT scans from the peripheral break to the most posterior aspect of the RRD, following its direction of progression. Sequential outer retinal morphologic changes observed using SS-OCT and associated VA at 3 months after surgery. Forty-nine eyes were included. The mean age (standard deviation [SD]) was 61.2 (15.2) years. The mean presenting logarithm of the minimum angle of resolution (SD) acuity was 1.09 (0.75). All stages observed on a high-definition horizontal 51-line scan were reported. Outer retinal changes occurred in 5 stages: (1) separation of the neurosensory retina from the retinal pigment epithelium (42/49, 85.7%); (2) thickening of inner and outer segments of photoreceptors (45/49, 91.8%); (3) outer retinal corrugation formation: (3a) low-frequency (44/49, 93.6%) and (3b) high-frequency outer retinal corrugations (42/49, 85.7%); (4) loss of the definition of outer retinal corrugations, with concurrent thickening of inner and outer segments (26/49, 53.1%); and (5) patchy (moth-eaten) or complete loss of inner and outer segments (17/49, 34.7%). The mean duration of fovea-off by stage in the parafovea (SD) was 2 (1.4), 2.3 (1.2), 11.4 (8.1), and 12 (13.3) days for stages 3a, 3b, 4, and 5, respectively. There was a statistically significant association between increasing stage of RRD and longer duration of foveal involvement (P= 0.001) and, most importantly, between increasing stage and worse VA at 3 months after surgery (P= 0.011). This novel staging system describes the sequential morphologic changes in RRD using SS-OCT. Increasing stage of RRD was associated with worse VA at 3 months after surgery. The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Nasal and temporal curvatures of lamina CRIBROSA in myopic eyes

Little is known about the myopic characteristics of lamina cribrosa (LC) curvature. As such, we investigated nasal and temporal LC curvatures in myopia. In this retrospective, cross-sectional study, 144 myopic eyes (refraction < − 2D) and 88 non-myopic eyes (refraction > − 0.5D) underwent swept-source optical coherence tomography scanning of the LC. The anterior border of LC curvature was delineated with 17 points and interpolated with the “cardinal spline” curve-fitting method. The average curvature indices of the temporal and nasal sides were presented as the temporal and nasal curvatures. Myopic eyes had a mean refraction of − 6.7 ± 2.8D, while for non-myopic eyes, the value was 0.3 ± 1.0D. Nasal LC curvature was visible in 54 myopia (37.5%) and 42 non-myopia (47.7%) cases (P = 0.126), and temporal LC curvature was visible in 142 myopia (98.6%) and 68 non-myopia (77.3%) cases (P = 0.001). The nasal LC curvature was significantly larger in myopia than in non-myopia (P < 0.001). Contrastingly, the temporal LC curvature was significantly smaller in myopia than in non-myopia (P < 0.001). Axial length was associated with larger nasal LC curvature, smaller temporal LC curvature, and larger nasal–temporal LC curvature difference (all P’s < 0.05). In myopic relative to non-myopic eyes, LC curvature was decreased temporally and increased nasally.

Automatic Quantitative Assessment of Lens Opacities Using Two Anterior Segment Imaging Techniques: Correlation with Functional and Surgical Metrics.

The purpose of this study is to quantitatively assess lens opacity, using a swept-source optical coherence tomography (SS-OCT) device for anterior segment assessment, and establish the correlation with Scheimpflug imaging, corrected distance visual acuity (CDVA) and cumulative dissipated energy (CDE). This prospective cross-sectional single-center study enrolled 51 patients (51 eyes) with crystalline lens opacity. Patients with previous ocular surgery, pathologies or general disorders affecting vision were excluded. Eyes were scanned with an SS-OCT device, and lens densitometry was automatically analyzed using a custom MATLAB script which examined lens density, nuclear density and linear density. The same analyses were performed on Scheimpflug images. Preoperative CDVA and CDE during phacoemulsification were recorded. Spearman’s (ρ) and Pearson’s (r) correlation coefficients were assessed according to data normality. Statistically significant correlations were established between SS-OCT and Scheimpflug imaging using lens analysis (ρ = 0.47, p < 0.001), nuclear analysis (ρ = 0.73, p < 0.001) and linear analysis (r = 0.44, p < 0.001). A significant correlation with CDE was found with all the SS-OCT methods (r = 0.57, p < 0.001). Only the nuclear analysis of the SS-OCT scans (Tb = −0.33, p < 0.01) and Pentacam Nucleus Staging (Tb = −0.26, p < 0.05) showed a statistically significant correlation with CDVA. Good inter-device agreement in lens densitometry was found. However, SS-OCT yielded improved lens imaging compared with the Scheimpflug device and a higher correlation with clinical parameters. Thus, high-resolution SS-OCT has the potential to become a preferable option for automatic cataract grading and preoperative planning.

A Deep Learning Model for Automated Segmentation of Geographic Atrophy Imaged Using Swept-Source OCT

To present a deep learning algorithm for segmentation of geographic atrophy (GA) using en face swept-source OCT (SS-OCT) images that is accurate and reproducible for the assessment of GA growth over time. Retrospective review of images obtained as part of a prospective natural history study. Patients with GA (n= 90), patients with early or intermediate age-related macular degeneration (n= 32), and healthy controls (n= 16). An automated algorithm using scan volume data to generate 3 image inputs characterizing the main OCT features of GA-hypertransmission in subretinal pigment epithelium (sub-RPE) slab, regions of RPE loss, and loss of retinal thickness-was trained using 126 images (93 with GA and 33 without GA, from the same number of eyes) using a fivefold cross-validation method and data augmentation techniques. It was tested in an independent set of one hundred eighty 6× 6-mm2 macular SS-OCT scans consisting of 3 repeated scans of 30 eyes with GA at baseline and follow-up as well as 45 images obtained from 42 eyes without GA. The GA area, enlargement rate of GA area, square root of GA area, and square root of the enlargement rate of GA area measurements were calculated using the automated algorithm and compared with ground truth calculations performed by 2 manual graders. The repeatability of these measurements was determined using intraclass coefficients (ICCs). There were no significant differences in the GA areas, enlargement rates of GA area, square roots of GA area, and square roots of the enlargement rates of GA area between the graders and the automated algorithm. The algorithm showed high repeatability, with ICCs of 0.99 and 0.94 for the GA area measurements and the enlargement rates of GA area, respectively. The repeatability limit for the GA area measurements made by grader 1, grader 2, and the automated algorithm was 0.28, 0.33, and 0.92 mm2, respectively. When compared with manual methods, this proposed deep learning-based automated algorithm for GA segmentation using en face SS-OCT images was able to accurately delineate GA and produce reproducible measurements of the enlargement rates of GA.

Impact of lens opacity and axial length on concomitant screening of maculopathy by swept-source optical coherence tomography-based optical biometer

BackgroundPreoperative evaluation of macular disorders is crucial to predict postoperative visual outcomes among patients with cataract. The swept-source optical coherence tomography (SS-OCT) based optical biometer was proved to be useful in screening macular pathology, while the impact of lens opacities and axial lengths on macular disease screening using SS-OCT based optical biometer remained unknown. This study aimed to evaluate the influence of lens opacities and axial lengths on foveal image quality detected by SS-OCT-based optical biometer, as well as sensitivity and specificity for the detection of macular diseases.MethodsThis was a diagnostic accuracy study that retrospectively included patients who underwent preoperative cataract examinations at our hospital between November 2020 and June 2021. All patients underwent SS-OCT based optical biometer and spectral-domain OCT (SD-OCT). The SD-OCT was the golden standard for diagnosing macular diseases. Sensitivity, specificity, and receiver operating characteristic (ROC) were calculated to evaluate the value of foveal SS-OCT scans for the detection of macular disease.ResultsOf the 224 eyes enrolled in the study, 82 eyes were diagnosed with macular disease by SD-OCT. The foveal image was almost indistinguishable due to poor quality when the mean grayscale of the image was less than 40. The posterior subcapsular opacity score and the axial length were significantly correlated with the gray density of the foveal image (r=−0.70, P<0.0001 and r=−0.40, P<0.0001). After excluding cases with indistinguishable foveal images (subcapsular opacities score ≥3.5, axial length ≥28.9 mm), the SS-OCT yielded 68% (95% confidence interval, 0.54–0.79) sensitivity and 87% (95% confidence interval, 0.78–0.92) specificity in 136 eyes.ConclusionsRoutine SS-OCT based biometric measurement for the evaluation of macular pathology simultaneously prior to cataract surgery is suggested except for patients with advanced cataract (posterior subcapsular opacities score ≥3.5) and long axial length (≥28.9 mm).

Three-Dimensional Volume Calculation of Intrachoroidal Cavitation Using Deep-Learning–Based Noise Reduction of Optical Coherence Tomography

PurposeIntrachoroidal cavitations (ICCs) are peripapillary pathological lesions generally associated with high myopia that can cause visual field (VF) defects. The current study aimed to evaluate a three-dimensional (3D) volume parameter of ICCs segmented from volumetric swept-source optical coherence tomography (SS-OCT) images processed using deep learning (DL)-based noise reduction and to investigate its correlation with VF sensitivity.MethodsThirteen eyes of 12 consecutive patients with peripapillary ICCs were enrolled. DL-based denoising and further analyses were applied to parapapillary 6 × 6-mm volumetric SS-OCT scans. Then, 3D ICC volume and two-dimensional depth and length measurements of the ICCs were calculated. The correlations between ICC parameters and VF sensitivity were investigated.ResultsThe ICCs were located in the inferior hemiretina in all eyes. ICC volume (P = 0.02; regression coefficient [RC], −0.007) and ICC length (P = 0.04; RC, −4.51) were negatively correlated with the VF mean deviation, whereas ICC depth (P = 0.15) was not. All of the parameters, including ICC volume (P = 0.01; RC, −0.004), ICC depth (P = 0.02; RC, −0.008), and ICC length (P = 0.045; RC, −2.11), were negatively correlated with the superior mean total deviation.ConclusionsWe established the volume of ICCs as a new 3D parameter, and it reflected their influence on visual function. The automatic delineation and 3D rendering may lead to improved detection and pathological understanding of ICCs.Translational RelevanceThis study demonstrated the correlation between the 3D volume of ICCs and VF sensitivity.

Depth-resolved visualization and automated quantification of hyperreflective foci on OCT scans using optical attenuation coefficients.

An automated depth-resolved algorithm using optical attenuation coefficients (OACs) was developed to visualize, localize, and quantify hyperreflective foci (HRF) seen on OCT imaging that are associated with macular hyperpigmentation and represent an increased risk of disease progression in age related macular degeneration. To achieve this, we first transformed the OCT scans to linear representation, which were then contrasted by OACs. HRF were visualized and localized within the entire scan by differentiating HRF within the retina from HRF along the retinal pigment epithelium (RPE). The total pigment burden was quantified using the en face sum projection of an OAC slab between the inner limiting membrane (ILM) to Bruch's membrane (BM). The manual total pigment burden measurements were also obtained by combining manual outlines of HRF in the B-scans with the total area of hypotransmission defects outlined on sub-RPE slabs, which was used as the reference to compare with those obtained from the automated algorithm. 6×6 mm swept-source OCT scans were collected from a total of 49 eyes from 42 patients with macular HRF. We demonstrate that the algorithm was able to automatically distinguish between HRF within the retina and HRF along the RPE. In 24 test eyes, the total pigment burden measurements by the automated algorithm were compared with measurements obtained from manual segmentations. A significant correlation was found between the total pigment area measurements from the automated and manual segmentations (P < 0.001). The proposed automated algorithm based on OACs should be useful in studying eye diseases involving HRF.

Choroidal Thickness in Eyes with Band Atrophy of the Optic Nerve from Chiasmal Compression.

Background The choroid is a vascular tissue that helps maintain retinal and prelaminar optic nerve head function. Choroidal thickness has been previously studied in diseases accompanied by retinal neural loss, but the relationship between the two sets of measurements is not clear. In eyes with temporal hemianopia as a result of chiasmal compression lesions (CCL), retinal neural loss tends to be greater in the nasal than the temporal hemiretina, a fact that may be useful in evaluating the effect of inner retinal layer loss on choroidal thickness. Purpose To evaluate macular and peripapillary choroidal thickness on swept-source optical coherence tomography (SS-OCT) in eyes with temporal hemianopia as a result of chiasmal compression and in healthy controls. Methods 33 eyes of 26 patients with band atrophy of the optic nerve and temporal visual field defects as a result of previously treated suprasellar tumors (CCL group) and 40 eyes of 21 healthy controls underwent SS-OCT scanning. The thickness of the peripapillary retinal nerve fiber layer (pRNFL), the peripapillary choroid (pChoroid), the macular RNFL (mRNFL), the macular ganglion cell layer (mGCL), and the macular choroid (mChoroid) was expressed globally and by sector (peripapillary quadrants and macular hemifield and quadrants). Ratios between macular nasal and temporal hemifield and quadrantic measurements were calculated using generalized estimated equation models, and the two groups were compared. Results The pRNFL, mRNFL, and mGCC thicknesses were significantly smaller in the CCL group than in the control group (64.67 ± 10.53 μm, 29.68 ± 5.80 μm, and 80.60 ± 10.17 μm vs. 103.78 ± 12.23 μm, 39.89 ± 3.82 μm, and 105.51 ± 7.76 μm, respectively; p < 0.001). For the choroid, the only difference between the groups was increased macular nasal hemifield and superonasal quadrant thickness in CCL (222.47 ± 61.05 μm and 230.45 ± 58.59 μm in the CCL group, respectively vs. 190.68 ± 52.54 μm and 197.65 ± 54.80 μm in the control group, respectively; p < 0.05). The temporal/nasal ratios were significantly higher for the mRNFL and mGCC parameters and significantly lower for the mChoroid parameters in the CCL group, except for the superotemporal/superonasal quadrant ratio. Conclusions The choroid does not thin after the inner retinal layer becomes damaged due to CCL and may even be thicker in some areas with corresponding severe retinal neural loss. While further studies are needed to interpret these findings, choroidal thinning is most likely not secondary to optic nerve disease-related inner retinal neural loss.

Analysis of choroidal structure and vascularity indices with image binarization of swept source optical coherence tomography images: A prospective study of 460 eyes.

PURPOSE:To evaluate choroidal vascularity index (CVI) among normal subjects using image binarization of swept source optical coherence tomography (SS-OCT).MATERIALS AND METHODS:Four hundred and sixty eyes of 230 normal participants were included. Total circumscribed choroidal area, luminal area, stromal area (SA), and CVI were derived from SS-OCT scans using open-source software (ImageJ) with the modified Niblack method. Both CVI and subfoveal choroidal thickness (SFCT) were correlated with age, refractive error, intraocular pressure, and mean ocular perfusion pressure (MOPP) using mixed linear model analysis. Pearson's correlation coefficient was used to determine the relationship between age and each dependent factor. Analyses were performed using the SPSS software version 20.0 (IBM Corp., Armonk USA) and statistical significance was tested at 5%.RESULTS:The mean age was 42.1 (±17.6) years. Mean SFCT was 307 ± 79 μm. Mean CVI was 66.80 (±3.8)%. There was statistically significant positive correlation between CVI and increasing age (r = 0.259, P < 0.0001) and statistically significant negative correlation between SFCT and age (r = −0.361, P < 0.0001). There was positive linear correlation between refractive error and CVI (r = 0.220, P < 0.0001) and negative correlation between SFCT and refractive error. There was no significant effect of MOPP on both CVI (P = 0.07) and SFCT (P = 0.7).CONCLUSION:CVI and SFCT are significantly correlated with age and refractive error in normal Indian eyes.

CHANGES IN THE CHOROIDAL THICKNESS AFTER MACULAR BUCKLING IN HIGHLY MYOPIC EYES.

To assess changes in the choroidal thickness (CT) after macular buckling in eyes with high myopia. Highly myopic eyes that underwent macular buckling surgery were retrospectively analyzed. Data of swept-source optical coherence tomography scanning at baseline and at 1, 3, 6, 12, and 18 months after macular buckling were collected. Subfoveal CT and CT at 750 µm superior, inferior, nasal, and temporal to the fovea were measured. The total choroidal area, vascular area, and stromal area were measured by the binarization method. The choroidal vascularity index was calculated by dividing the vascular area by the total choroidal area. Forty-one eyes were included in the final analysis. The subfoveal CT increased from 49.85 ± 31.23 µm preoperatively to 75.74 ± 37.89 µm 1 month after macular buckling (P < 0.001), then decreased over time, coinciding with the trends of parafoveal CT, total choroidal area, vascular area, and stromal area. The subfoveal CT was restored to the preoperative level six months postoperatively (P = 0.202) and remained stable until the end of follow-up. The choroidal vascularity index increased at 1 and 3 months postoperatively (P = 0.001 and 0.005, respectively). The choroid thickened in the early postoperative period. The compression force of the buckle implant might disturb microcirculatory drainage and contribute to the thickening. The choroid spontaneously recovered to the preoperative level over time.

Utility of IOLMaster 700 Swept-Source Optical Coherence Tomography in Detecting Macular Disease for Preoperative Cataract Surgery Patients.

PurposeTo assess the efficacy of IOLMaster 700 (IOLM) biometer swept-source optical coherence tomography (SS-OCT) in detecting macular pathology before cataract surgery and to compare IOLM SS-OCT characteristics of foveal pathology with a widely used spectral-domain OCT (SD-OCT) system.Patients and MethodsRetrospective analysis of 1156 consecutive eyes with IOLMaster 700 SS-OCT undergoing cataract surgery from January to June 2017 was performed. Approximately a third of these eyes (327 eyes) also had a SD-OCT scan performed previously. A single reviewer assessed each SS-OCT scan and identified them as “normal” or “abnormal.” SS-OCT sensitivity and specificity in identifying foveal pathology was assessed using findings on Spectralis SD-OCT scans as the gold standard.ResultsOf 327 eyes with both IOLM SS-OCT and Spectralis SD-OCT scans, 121 eyes (37.0%) had abnormal SS-OCT scans. Of these 121 eyes, SD-OCT scans confirmed pathology in 104 eyes (86.0%). Of the remaining 206 eyes graded to have normal SS-OCT scans, 84 eyes (40.8%) had normal SD-OCT scans, and 122 eyes (59.2%) had pathologic findings on SD-OCT scans. For each pathologic condition, subtle but definitive differences existed in the appearance of the IOLM SS-OCT and SD-OCT images.ConclusionUsing a normal or abnormal Spectralis SD-OCT scan as confirmation of absence or presence of foveal pathology respectively, we found a high positive predictive value (86.0%) of an abnormal IOLM SS-OCT scan and a high specificity (83.2%) but low sensitivity (46.0%) and negative predictive value (40.8%) of a normal-appearing SS-OCT scan. These results suggest that an abnormal IOLM SS-OCT scan in an eye without known pathology is a strong indicator of an abnormal macula and should prompt further evaluation of the retina to identify pathology prior to cataract surgery. Importantly, IOLM SS-OCT scans do not detect all macular pathology and cannot be used as a screening test for identifying macular pathology.

An en face swept source optical coherence tomography study of the vitreous in eyes with anterior uveitis.

To analyse vitreous anatomy patients with anterior uveitis (AU) using swept source optical coherence tomography (SS-OCT). Patients with newly diagnosed AU and healthy participants were scanned using 16-mm SS-OCT B-scans and 12 × 12 mm cube centred at the fovea. Linear SS-OCT scans were evaluated to identify the premacular bursa (PB) above the macula and the Cloquet's canal above the optic disc. A dynamic evaluation of the 12 × 12 mm cube enabled en face measurement of the vertical and horizontal diameters of the PB and the presence/absence of communication between the PB and Cloquet's canal. One hundred and thirty-five subjects were included in the study. Forty-five patients were healthy (mean age 33.47 years). En face measurements of the horizontal and vertical PB mean diameters were 5.2 mm and 4.7 mm. In 90 subjects with AU (mean age 30.10 years), the mean horizontal and vertical diameter of the PB were significantly larger (p < 0.01). Thirty-seven eyes with AU presented with cystoid macular oedema (CME). The mean diameters of the PB in this subgroup were significantly larger (p < 0.01). In 75% of the entire cohort (51% of eyes in the control group, 87% of eyes with AU and 100% of eyes with AU and CME), a channel connecting the PB and Cloquet's canal could be identified. SS-OCT identification of a connecting channel between the PB and the Cloquet's canal suggests that inflammatory cytokines may drain from the anterior chamber through this system of channels, thus increasing the risk of CME.

Imaging Features by Machine Learning for Quantification of Optic Disc Changes and Impact on Choroidal Thickness in Young Myopic Patients.

Purpose: To construct quantifiable models of imaging features by machine learning describing early changes of optic disc and peripapillary region, and to explore their performance as early indicators for choroidal thickness (ChT) in young myopic patients.Methods: Eight hundred and ninety six subjects were enrolled. Imaging features were extracted from fundus photographs. Macular ChT (mChT) and peripapillary ChT (pChT) were measured on swept-source optical coherence tomography scans. All participants were divided randomly into training (70%) and test (30%) sets. Imaging features correlated with ChT were selected by LASSO regression and combined into new indicators of optic disc (IODs) for mChT (IOD_mChT) and for pChT (IOD_pChT) by multivariate regression models in the training set. The performance of IODs was evaluated in the test set.Results: A significant correlation between IOD_mChT and mChT (r = 0.650, R2 = 0.423, P < 0.001) was found in the test set. IOD_mChT was negatively associated with axial length (AL) (r = −0.562, P < 0.001) and peripapillary atrophy (PPA) area (r = −0.738, P < 0.001) and positively associated with ovality index (r = 0.503, P < 0.001) and torsion angle (r = 0.242, P < 0.001) in the test set. Every 1 × 10 μm decrease in IOD_mChT was associated with an 8.87 μm decrease in mChT. A significant correlation between IOD_pChT and pChT (r = 0.576, R2 = 0.331, P < 0.001) was found in the test set. IOD_pChT was negatively associated with AL (r = −0.478, P < 0.001) and PPA area (r = −0.651, P < 0.001) and positively associated with ovality index (r = 0.285, P < 0.001) and torsion angle (r = 0.180, P < 0.001) in the test set. Every 1 × 10 μm decrease in IOD_pChT was associated with a 9.64 μm decrease in pChT.Conclusions: The study introduced a machine learning approach to acquire imaging information of early changes of optic disc and peripapillary region and constructed quantitative models significantly correlated with choroidal thickness. The objective models from fundus photographs represented a new approach that offset limitations of human annotation and could be applied in other areas of fundus diseases.