Optical Coherence Tomography Scans Research Articles

CNN-Based Device-Agnostic Feature Extraction From ONH OCT Scans.

Optical coherence tomography (OCT)-derived measurements of the optic nerve head (ONH) from different devices are not interchangeable. This poses challenges to patient follow-up and collaborative studies. Here, we present a device-agnostic method for the extraction of OCT biomarkers using artificial intelligence. ONH-centered OCT volumes from the Heidelberg SPECTRALIS, ZEISS CIRRUS HD-OCT 5000, and Topcon 3D OCT-1000 Mark I/II and 3D OCT-2000 devices were annotated by trained graders. A convolutional neural network (CNN) was trained on these segmented B-scans and utilized to obtain several ONH biomarkers, such as the retinal nerve fiber layer (RNFL) and the minimal rim width (MRW). The CNN results were compared between different devices and to the manufacturer-reported values using an independent test set. The intraclass correlation coefficient (ICC) for the circumpapillary retinal nerve fiber layer (cpRNFL) at 3.4 mm reported by the CIRRUS and 3D OCT-2000 was 0.590 (95% confidence interval [CI], -0.079 to 0.901), and our CNN resulted in a cpRNFL ICC of 0.667 (95% CI, -0.035 to 0.939). The cpRNFL at 3.5 mm on the CIRRUS, 3D OCT-2000, and SPECTRALIS generated by the CNN resulted in an ICC of 0.656 (95% CI, 0.055-0.922). Comparing the global mean MRWs from the SPECTRALIS between CNN and manufacturer yielded an ICC of 0.983 (95% CI, 0.917-0.997). The CNN ICC for the MRW among the CIRRUS, 3D OCT-2000, and SPECTRALIS was 0.917 (95% CI, 0.947-0.981). Our device-agnostic feature extraction from ONH OCT scans showed a higher reliability than the measures generated by the manufacturers for cpRNFL. MRW measurements compared very well among the manufacturers. This open-source software can robustly extract a wide range of biomarkers from any OCT device, removing the dependency on manufacturer-specific algorithms, which has significant implications for patient follow-up and collaborative research.

Dynamics-aware deep predictive adaptive scanning optical coherence tomography

Dynamics-aware deep predictive adaptive scanning optical coherence tomography

Effects of Anatomical Variation on Ganglion Cell and Nerve Fibre Layer Evaluation by Optical Coherence Tomography

Background/Objectives: The automated analyses of optical coherence tomography (OCT) scans of the retina occasionally suggest the presence of tissue deficits when no visual field defects can be detected. This study was made to find the sources of such alerts. Methods: Data from a population-based cohort of 360 participants aged 30–80 years was analysed for the anatomical sources of alerts after the extensive exclusion of participants where any suspicion of abnormality could be raised. An analysis was made of 12 × 9 mm volume scans centred between the disc and the fovea. The exclusions comprised 107 eyes with definite or borderline abnormal visual fields or other potentially confounding characteristics. A statistical analysis of the thickness patterns was made using the manufacturer’s proprietary algorithm. The analysis comprised alerts corresponding to local layer thickness values in the lower 5th percentile of an independent reference population. Results: Of the 613 eligible healthy eyes, thickness deficit alerts were seen in 391. They were related to the angle between the temporal nerve fibre ridges being wider, narrower, or rotated compared to the reference template in 174 eyes and to the variations in the size of the macula in 207 eyes. The source was unidentifiable in 28 eyes. The common sources were a thin papillomacular nerve fibre layer accompanied by arcuate nerve fibre ridges spaced far apart and a thinly, but wider than the normal macular ganglion cell layer. Conclusions: Anatomical variation in the retinal nerve fibre and ganglion cell layers was the source of more than 90% of the thickness deficit alerts in the eyes with normal visual fields.

Optical Coherence Tomography of the Corn Snake (Pantherophis guttatus) Eye: An Exploratory Study

Abstract The aim of this exploratory study was to capture images of the anterior and posterior segments of the corn snake eye using spectral domain optical coherence tomography (OCT). Post-mortem OCT scans were conducted on three euthanized corn snakes (Pantherophis guttatus), followed by a histological examination of their eyes. OCT findings were correlated with histology to identify anterior and posterior ocular structures, and to delineate retinal layers on OCT. Total retinal thickness (RT) was manually measured every 360 μm from the edge of the optic disc over a 3600 μm distance in the dorsal and ventral quadrant of each snake. In the anterior segment of the eye, OCT imaging successfully identified the spectacle, cornea, iris, lens and Schlemm’s canal. The posterior segment scans revealed a vestigious conus papillaris and retinal folds adjacent to the optic nerve head which were confirmed by histology. The membrana vasculosa was distinguishable from the surrounding retina, and despite some limitations in image resolution, retinal layers were discernible. There was a positive correlation between the total RT and the distance from the optic disc (with the retina being thicker farther from the optic disc). Additionally, the total RT in the ventral quadrant was significatively lower than in the dorsal quadrant. OCT imaging effectively identified various anatomical features and retinal layers of the corn snake’s eye. To establish comprehensive OCT references for the posterior segment of the eye, further studies involving healthy, living snakes are needed.

Refined speckle contrast estimation in OCT based on compensation of scattering-related distortions of speckle pattern parameters

Abstract Speckle contrast (SC) parameters in optical coherence tomography (OCT) scans are formed by the interplay of several factors—local level of optical wave backscattering by the material inhomogeneities, parameters of spatial distribution of the latter and the degree of cumulative optical wave attenuation during its fourth-and-back propagation. For the optical wavelengths used in OCT, this attenuation is usually dominated by the influence of scattering in the visualized turbid tissues rather than by absorption. For sufficiently high concentrations of scatterers (at least a few scatterers in the coherence volume) characterized by comparable scattering strengths and a fairly homogeneous distribution in space, the interference of locally scattered waves should be characterized by a Rayleigh distribution of speckle amplitudes, for which the local SC tends to 0.52. Equivalently, in terms of speckle intensities, the local SC tends to unity. Local spatial inhomogeneities or strongly uneven scattering strengths lead to the appearance of increased values of SC, which may serve as a diagnostic feature of some tissue components in OCT images. At the same time, in comparison to surface speckles formed by coherent-light scattering from rough surfaces, OCT-beam attenuation during its fourth-and-back propagation may introduce intensity inhomogeneities in OCT scans even for homogeneous tissue areas. This effect results in artefactual distortion of the visible SC in comparison with the above-mentioned expected value. Moreover, the presence of individual strong scatterers may additionally non-locally distort SC values due to the appearance of elongated shadows below such scatterers, which causes lateral inhomogeneities in OCT scans. Here, we propose a refined SC parameter, which is cleaned from distorting scattering-related effects in both axial and lateral directions. Depth-resolved estimation of the optical attenuation coefficient is used to restore attenuation-free OCT scans, for which the refined SC is estimated. The efficiency of the proposed approach is demonstrated using both digital OCT phantoms with highly controlled properties and experimental OCT data.

Detection of Disease Features on Retinal OCT Scans Using RETFound

Eye diseases such as age-related macular degeneration (AMD) are major causes of irreversible vision loss. Early and accurate detection of these diseases is essential for effective management. Optical coherence tomography (OCT) imaging provides clinicians with in vivo, cross-sectional views of the retina, enabling the identification of key pathological features. However, manual interpretation of OCT scans is labor-intensive and prone to variability, often leading to diagnostic inconsistencies. To address this, we leveraged the RETFound model, a foundation model pretrained on 1.6 million unlabeled retinal OCT images, to automate the classification of key disease signatures on OCT. We finetuned RETFound and compared its performance with the widely used ResNet-50 model, using single-task and multitask modes. The dataset included 1770 labeled B-scans with various disease features, including subretinal fluid (SRF), intraretinal fluid (IRF), drusen, and pigment epithelial detachment (PED). The performance was evaluated using accuracy and AUC-ROC values, which ranged across models from 0.75 to 0.77 and 0.75 to 0.80, respectively. RETFound models display comparable specificity and sensitivity to ResNet-50 models overall, making it also a promising tool for retinal disease diagnosis. These findings suggest that RETFound may offer improved diagnostic accuracy and interpretability for specific tasks, potentially aiding clinicians in more efficient and reliable OCT image analysis.

Extracting full information from OCT scans-signs of early age-related macular degeneration within inner retinal layers by local neighbourhood statistics. Part II: Results.

Associations between the occurrence of early age related macular degeneration (AMD) and alterations in retinal layer thicknesses have been reported, based on classical processing of optical coherence tomography (OCT) data by noise removal and subsequent image segmentation. However, speckle noise within OCT data itself bears a substantial part of the total information. For this reason, we designed an omics-type approach for full exploitation of OCT data, which was able to identify signs of early AMD throughout the retina as a whole. A nested case-control study was designed with 200 early AMD cases and 200 healthy controls. For each participant, within a randomly selected OCT scan and a randomly selected column therein, manual grading was performed for 26 retinal feature positions. At every position, a total of 3792 descriptors were computed, based on nonlinear transformations of OCT data, first-order neighbourhood statistics and Haralick features. Equivalence and differences between cases and controls were tested for each descriptor at every graded position. Results of multiple testing were expressed in terms of false and true discovery rates controlled by the Benjamini-Yekutieli procedure. In terms of the amount and disparity of true discoveries, overall non-equivalence was found for early AMD and healthy groups. Strong difference signals were observed at the internal limiting membrane and two central retinal positions, particularly for descriptors emphasising speckle noise. Between the retinae of healthy controls and early AMD patients, significant differences were observed at the level of local neighbourhood statistics within OCT data. Thus, independent evidence was obtained for AMD affecting not only the outer retinal layers but the retina as a whole, even in the early stages of the disease. Within OCT data, both cartoon and speckle bear essential parts of the total information. We pursued a constructive, completely documented, traceable and repeatable approach without invoking artificial intelligence methods.

Extracting full information from OCT scans-signs of early age-related macular degeneration within inner retinal layers by local neighbourhood statistics. Part I: Methodology.

Associations between the occurrence of early age-related macular degeneration (AMD) and alterations in retinal layer thicknesses have been reported based on classical processing of optical coherence tomography (OCT) data by noise removal and subsequent image segmentation. However, speckle noise within OCT data itself bears a substantial part of the total information. For this reason, an omics-type approach was designed for full exploitation of OCT data, which was able to identify signs of early AMD throughout the retina as a whole. A nested case-control study was designed with 200 early AMD cases and 200 healthy controls. For every participant, within a randomly selected OCT scan and a randomly selected column therein, manual grading was performed for 26 retinal feature positions. At each position, a total of 3792 descriptors were computed, based on nonlinear transformations of OCT data, first-order neighbourhood statistics and Haralick features. Equivalence and differences between cases and controls were tested for every descriptor at each graded position. Results of multiple testing were expressed in terms of false and true discovery rates controlled by the Benjamini-Yekutieli procedure. In terms of the amount and disparity of true discoveries, overall non-equivalence of early AMD and healthy groups was found. Strong difference signals were observed at the internal limiting membrane and two central retinal positions, particularly for descriptors emphasising speckle noise. Between retinae of healthy controls and early AMD patients, significant differences were observed at the level of local neighbourhood statistics within the OCT data. Thus, independent evidence was obtained for AMD affecting not only the outer retinal layers but also the retina as a whole, even in the early stages of the disease. Within OCT data, both cartoons and speckle bear essential parts of total information. A constructive, completely documented, traceable and repeatable approach was pursued without invoking artificial intelligence methods.

Three-Dimensional Choroidal Vessels Assessment in Age-Related Macular Degeneration.

To compare the choroidal vasculature in eyes with early- and intermediate-stage age-related macular degeneration (dAMD) and healthy using a novel three-dimensional algorithm. Patients with dAMD and healthy controls underwent clinical examinations and swept-source optical coherence tomography scans (PlexElite-9000 device) centered on the fovea. Scans with quality scores >6 were included. Eyes with any signs of neovascular AMD or geographic atrophy were excluded. The choroidal layer was segmented using ResUNet model and volumetric smoothing. Phansalkar thresholding was used to binarize the choroidal vasculature. The three-dimensional maps were divided into five sectors. The three largest vessels in each sector were measured to determine the mean choroidal vessel diameter (MChVD) and inter-vessel distance (IVD). Volumetric choroidal thickness (ChT) and vascularity index (CVI) were also calculated. This retrospective cross-sectional study analyzed 60 eyes from 45 dAMD patients (27 early-stage, 33 intermediate-stage) and 26 eyes from 16 healthy controls. The average MChVD was increased in dAMD eyes compared to healthy eyes (239.559 ± 47.058 µm vs. 197.873 ± 49.047 µm, P < 0.001). The average MChVD in each sector increased significantly in eyes with dAMD (P < 0.05). The average IVD was increased significantly in dAMD eyes compared to healthy eyes (234.128 ± 69.537 µm vs. 179.914 ± 49.995 µm, P < 0.001). The average IVD in each sector was significantly increased in eyes with dAMD (P < 0.05). Average ChT and CVI in dAMD were reduced compared to healthy eyes (P < 0.05). Eyes with dAMD demonstrated increased MChVD and IVD and decreased ChT and CVI, possibly related to smaller-vessel atrophy and larger-vessel dilation.

Characteristics of submacular hemorrhage with bacillary layer detachment and intrabacillary hemorrhage.

To study the outcomes of patients presenting with submacular hemorrhage (SMH) and bacillary layer detachment (BALAD) following intervention. This retrospective study examined fundus photographs and optical coherence tomography (OCT) scans to identify treatment-naive SMH and BALAD cases. Two groups were formed: SMH cases with and without BALAD. The treatment outcomes of these cases were assessed. Thirteen (65%) of the 20 eyes with SMH had BALAD. Blunt trauma was the most common cause of SMH (n = 10, 50%). Median age was 46 years (IQR range: 28-70). Demographic, clinical, or OCT imaging findings between the groups (p > 0.05) were comparable. Nine (45%) patients each underwent intravitreal gas injection alone or along with PPV and TpA injection. At 1-month post-treatment, VA improved (logMAR VA - 0.89; p = 0.017). BALADs and intrabacillary hemorrhage had resolved in eight (61%) cases. Intraretinal, subretinal, and sub-RPE fluids resolved in 100%, 70%, and 43% of cases, respectively. Eyes with resolved BALAD showed greater improvement in VA (logMAR VA - 0.98) than eyes with persisting BALAD (logMAR VA - 1.1) and resulted in significant decrease in central macular (p = 0.016) and retinal thicknesses (p = 0.031). SMH eyes without pre-treatment BALAD also observed statistically significant improvement in visual acuity following intervention (p = 0.031). BALAD and intrabacillary hemorrhage in SMH are relatively common. A significant proportion of cases had their BALAD and intrabacillary haemorrhage resolved following treatment. Persistence of BALAD had no effect on VA.

Earliest location of glaucomatous retinal nerve fibre layer damage is determined by intact baseline RNFL thickness profile

Background/aimsTo identify whether an intact retinal nerve fibre layer (RNFL) thickness profile could determine the location of the earliest RNFL defect in glaucoma.MethodsRetrospective longitudinal cohort study of patients with initial...

Paramagnetic rim lesions are associated with inner retinal layer thinning and progression independent of relapse activity in multiple sclerosis.

Paramagnetic rim lesions (PRLs) are chronic active lesions associated with a severe disease course in multiple sclerosis (MS). This study was undertaken to investigate an association between retinal layer thinning (annualized loss of peripapillary retinal nerve fiber layer [aLpRNFL] and ganglion cell-inner plexiform layer [aLGCIPL]) and PRLs in patients with MS (pwMS). In this study, pwMS with brain magnetic resonance imaging and ≥2 optical coherence tomography scans were included. Cox proportional hazard regression models were performed using progression independent of relapse activity (PIRA) as the dependent variable, and aLpRNFL, aLGCIPL, or the number of PRLs as independent variables, adjusted for covariates. We analyzed data from 97 pwMS (mean age = 35.2 years [SD = 9.9], 71.1% female, median disease duration = 2.3 years [interquartile range = 0.9-9.0]). The number of PRLs was associated with aLpRNFL and aLGCIPL. PIRA was observed in 18 (18.6%) pwMS, with aLpRNFL (hazard ratio [HR] = 1.44 per %/year), aLGCIPL (HR = 1.61 per %/year), and the number of PRLs (HR = 1.24 per PRL) being associated with increased risk of PIRA. The number of PRLs is associated with inner retinal layer thinning and increased risk of PIRA. A combination of PRLs and retinal layer thinning could serve as a surrogate for pwMS at highest risk of disability progression.

Optical coherence tomography characteristics in hydroxychloroquine retinopathy and the correlations with visual deterioration in Taiwanese

Abstract PURPOSE: This study aimed to investigate optical coherence tomography (OCT) characteristics in hydroxychloroquine (HCQ) retinopathy and their correlation with visual acuity among Taiwanese patients. MATERIALS AND METHODS: We retrospectively recruited patients undergoing long-term HCQ treatment who had received examinations of best-corrected visual acuity and OCT scans. We observed disruptions in the ellipsoid zone (EZ) and retinal pigment epithelium (RPE) across different retinal regions. Principal component analysis (PCA) was employed to identify the most significant factors associated with visual deterioration. RESULTS: Among the 120 eyes included in the study, HCQ retinopathy was present in 42 eyes (35.0%). In patients with mild-to-moderate retinopathy, the pericentral pattern was predominant (75.0%), whereas no parafoveal pattern was observed. Serial examinations revealed that lesions typically progressed from pericentral to parafoveal and foveal regions. EZ disruption was observed in all affected cases, most frequently at the pericentral region (100%), followed by the perifoveal (87.4%), parafoveal (72.1%), and foveal (43.2%) regions. RPE disruption was noted in 59.5% of cases, with the highest prevalence at the pericentral (53.2%) and perifoveal (52.3%) regions, followed by the parafoveal (33.3%) and foveal (28.8%) regions. PCA identified RPE disruption at the fovea and parafoveal regions as the most strongly correlated factors for visual deterioration. CONCLUSIONS: In Taiwanese patients, HCQ retinopathy predominantly manifests with pericentral lesions, while isolated parafoveal lesions are rare as an initial presentation. RPE disruption, rather than EZ disruption, appears to be the primary determinant for visual deterioration in this population.

Diagnosing glaucoma progression with optical coherence tomography.

Optical coherence tomography (OCT) is a widely used tool to diagnose and monitor glaucoma by objectively measuring the ganglion cell layer and the retinal nerve fiber layer (RNFL) thickness. The presence of RNFL thinning raises suspicion for glaucoma progression. Therefore, this review aims to discuss current approaches to using OCT for detecting glaucomatous change, limitations, and recent advancements. Previously established approaches to determining glaucomatous progression on OCT include quantitative and qualitative methods. The most common quantitative methods include event-based and trend-based analysis. Decreasing RNFL thickness or loss of the ganglion cell layer are indicative of glaucomatous changes. However, interpretation of OCT scans is strongly impacted by artifacts, which can be because of epiretinal membrane or posterior vitreous detachment. Race and aging also may impact interpretation of RNFL progression. More recent research focuses on loss of the RNFL because of the effects of systemic conditions. Given the limitations in the current approaches, recent advancements indicate a promising role for artificial intelligence in determining true glaucomatous progression. This review highlights current approaches to identifying glaucoma progression on OCT, limitations to these approaches, and the potential role for artificial intelligence.

Seasonal Variation in ATP-Induced Retinal Damage in the Cone-Dominant 13-Lined Ground Squirrel.

To examine whether time of year (relative to hibernation emergence) influences the retinal degenerative effects of intravitreal injection of adenosine triphosphate (ATP) in the 13-lined ground squirrel (13-LGS). Eighteen (9 male, 9 female) 13-LGS in three experimental cohorts (early season, mid-season, late season) (n = 6 each) underwent baseline imaging using scanning light ophthalmoscopy (SLO) and optical coherence tomography (OCT). Animals then received a 10-µL intravitreal injection of 0.723 M ATP, followed by OCT and SLO imaging at 3, 10, and 21 days. Adaptive optics SLO (AOSLO) was performed in animals without retinal damage after the 21-day follow-up. Retinal thickness, choroidal thickness, and cone density measures were compared to values from wild-type controls (n = 12). Five animals (four early season, one late season) showed retinal damage post-ATP injection (Fisher's exact test, P = 0.065). Animals with retinal damage displayed areas of disrupted retinal lamination on OCT. Any changes in OCT thickness were generally present on initial follow-up and resolved at later time points. Follow-up imaging with AOSLO on animals without retinal damage showed no significant differences in the cone mosaic topography from control eyes. Axial length was increased in mid-/late-season cohorts relative to early season (P = 0.0025 and P = 0.0007). In this pilot study, the 13-LGS appears more susceptible to ATP-induced retinal damage during the early season. Future studies adjusting dose based on ocular biometry may help elucidate the impact of time of year on chemical response. Consideration of ocular biometry in this and other animal models is merited when using intravitreal methods of chemical administration.

Impact of the Valsalva manoeuvre on the choroid: A systematic review with meta-analyses.

A variety of daily activities can intentionally or unintentionally cause the Valsalva manoeuvre, which induces a physiological response of elevated peripheral venous pressure. Studies have speculated that it may ultimately affect the choroidal anatomy. This is particularly important from a clinical point-of-view since patients occasionally hold their breath while undergoing macular optical coherence tomography (OCT). In this study, we systematically reviewed the literature to understand the impact of the Valsalva manoeuvre on the choroid and conducted meta-analyses on the changes induced in the subfoveal choroidal thickness (SFCT) and the choroidal vascularity index (CVI). We searched 12 literature databases for studies in healthy participants undergoing Valsalva manoeuvre with choroidal OCT scans before and during the manoeuvre. Seven studies with a total of 444 eyes of 279 individuals were eligible for the review. The Valsalva manoeuvre led to a statistically significant but numerically small increase in the SFCT of 6.5 μm (95% CI: 1.6-11.4 μm; p = 0.01) and a statistically significant increase in the CVI of 1.48 (95% CI: 1.23-1.73; p = 0.0002). Thus, the Valsalva manoeuvre has a measurable impact on the choroid, and we recommend careful observation of how the patient sits and behaves behind the OCT scanner while scanning in order to allow accurate measurements of the choroid for diagnosis and monitoring.

A small disc size, a big challenge: effect of optic disc size on the correlation between peripapillary choroidal thickness, peripapillary retinal nerve fiber layer, and ganglion cell layer.

We aimed to analyze the effect of optic disc size on the correlation between the peripapillary choroid (PPC), peripapillary retinal nerve fiber layer (RNFL), and macular ganglion cell inner plexiform layer (MGCIPL) thicknesses in subjects with ocular hypertension (OHT) and primary open angle glaucoma (POAG). This study included 61 eyes with a disc area (DA) of ≤ 1.63 mm2, 92 eyes with a DA of 1.63-2.42 mm2, and 59 eyes with a DA of ≥ 2.42 mm2 in small disc, regular disc, and large disc groups, respectively. The swept-source optical coherence tomography scans of the PPC, RNFL, and MGCIPL were analyzed according to disc size. The three groups did not significantly differ in RNFL or MGCIPL measurements, but the PPC measurement was statistically significantly higher in the small disc group and statistically significantly thinner in the large disc group. Most of the correlations observed between the RNFL and MGCIPL measurements and eye characteristics in the regular disc group were not detected in the small and large disc groups. While the RNFL and MGCIPL were well correlated in all disc size groups, the PPC did not correlate with the RNFL or MGCIPL in any of the groups. Overall, the RNFL and MGCIPL measurements were consistent across all three disc sizes. While the PPC was thicker in small discs than in larger discs, it was not correlated with the RNFL or MGCIPL.

Multi-modal representation learning in retinal imaging using self-supervised learning for enhanced clinical predictions

Self-supervised learning has become the cornerstone of building generalizable and transferable artificial intelligence systems in medical imaging. In particular, contrastive representation learning techniques trained on large multi-modal datasets have demonstrated impressive capabilities of producing highly transferable representations for different downstream tasks. In ophthalmology, large multi-modal datasets are abundantly available and conveniently accessible as modern retinal imaging scanners acquire both 2D fundus images and 3D optical coherence tomography (OCT) scans to assess the eye. In this context, we introduce a novel multi-modal contrastive learning-based pipeline to facilitate learning joint representations for the two retinal imaging modalities. After self-supervised pre-training on 153,306 scan pairs, we show that such a pre-training framework can provide both a retrieval system and encoders that produce comprehensive OCT and fundus image representations that generalize well for various downstream tasks on three independent external datasets, explicitly focusing on clinically pertinent prediction tasks. In addition, we show that interchanging OCT with lower-cost fundus imaging can preserve the predictive power of the trained models.

Proposing a Methodology for Axon-Centric Analysis of IOP-Induced Mechanical Insult.

IOP-induced mechanical insult on retinal ganglion cell axons within the optic nerve head (ONH) is believed to be a key factor in axonal damage and glaucoma. However, most studies focus on tissue-level mechanical deformations, overlooking that axons are long and thin, and that their susceptibility to damage likely depends on the insult's type (e.g. stretch/compression) and orientation (longitudinal/transverse). We propose an axon-centric approach to quantify IOP-induced mechanical insult from an axon perspective. We used optical coherence tomography (OCT) scans from a healthy monkey eye along with histological images of cryosections to reconstruct the axon-occupied volume including detailed lamina cribrosa (LC) pores. Tissue-level strains were determined experimentally using digital volume correlation from OCT scans at baseline and elevated IOPs, then transformed into axonal strains using axon paths estimated by a fluid mechanics simulation. Axons in the LC and post-LC regions predominantly experienced longitudinal compression and transverse stretch, whereas those in the pre-LC and ONH rim mainly suffered longitudinal stretch and transverse compression. No clear patterns were observed for tissue-level strains. Our approach allowed discerning axonal longitudinal and transverse mechanical insults, which are likely associated with different mechanisms of axonal damage. The technique also enabled quantifying insult along individual axon paths, providing a novel link relating the retinal nerve fiber layer and the optic nerve through the LC via individual axons. This is a promising approach to establish a clearer connection between IOP-induced insult and glaucoma. Further studies should evaluate a larger cohort.

Automated Detection of Drusenoid Pigment Epithelial Detachments From Spectral-Domain Optical Coherence Tomography in Patients With AMD.

This study aimed to develop an algorithm for automated detection of drusenoid pigment epithelial detachments (DPEDs) in optical coherence tomography (OCT) volumes of patients with age-related macular degeneration (AMD) and to compare its performance against traditional reading center grading on color-fundus photographs (CFPs). Eyes with a range of AMD severities, excluding neovascular disease, were imaged using spectral-domain OCT (SD-OCT) and paired CFPs and were followed annually for up to 5years. DPEDs were automatically identified by segmenting the retinal pigment epithelium (RPE) and Bruch's membrane (BM) layers from the SD-OCT volumes and imposing both a minimum RPE BM height (>75 µm) and a two-dimensional length requirement (>433 µm). Comparisons in detection rates and contoured areas were made between the algorithmic SD-OCT detections and manually graded and contoured CFPs. Of the 1602 visits for the 323 eyes, the automated OCT algorithm identified 139 visits (8.7%) from 50 eyes with DPED, but a reading center review of paired CFPs identified 23 visits (1.4%) from nine eyes as having DPEDs. Eyes identified with DPEDs on OCT received nine-step AMD severity scores ranging from 6 to 10, and those scores had occurrence ratios of 23/160 (14%), 89/226 (39%), 24/99 (24%), 2/63 (3%), and 1/29 (3%), respectively. On a subset of 25 visits that also underwent manual contouring of DPED lesions in CFP, the Pearson correlation coefficient for DPED areas observed by OCT and CFP was 0.85. Our analysis shows the feasibility of using OCT scans to objectively detect features that historically have been detected qualitatively by expert graders on CFPs. Automated detection and quantitation of high-risk features can facilitate screening patients for clinical-trial enrollment and could serve as an outcome metric [T1 (Translation-to-Humans) and T4 (Translation-to-Population-Health)].