BACKGROUND: To compare the repeatability and reproducibility of corneal and corneal epithelial thickness mapping using anterior segment optical coherence tomography (AS-OCT) according to tear film break-up time (TBUT).
METHODS: The included eyes were divided into three subgroups according to TBUT (group 1: TBUT ≤ 5 s, group 2: 5 s < TBUT ≤ 10 s, and group 3: TBUT > 10 s). All eyes were imaged separately thrice by two operators to obtain the thickness maps (TMs) of the cornea and corneal epithelium based on spatial zones encompassing a 9-mm-diameter area. Each TM consisted of 25 areas. Intraoperator (repeatability) and interoperator (reproducibility) standard deviations (Sws), coefficients of variation (CoVs), and intraclass correlation coefficients (ICCs) among the tests were calculated and compared in all the areas.
RESULTS: Altogether, 132 eyes of 67 subjects were included (50, 47, and 35 eyes in groups 1, 2, and 3; respectively). The ICCs of corneal epithelial thickness and corneal thickness were > 0.75 in most of the areas. Pairwise comparisons showed that AS-OCT exhibited lower repeatability in group 1 than in groups 2 and 3 (P < 0.05). However groups 2 and 3 showed similar results. Sws and CoVs of corneal epithelial thickness exhibited no significant interoperator differences. While no significant differences were observed in corneal thickness in most of the areas.
CONCLUSIONS: TBUT significantly influences the repeatability of corneal and corneal epithelial thickness measurements. Poor tear film stability requires careful evaluation of corneal epithelial thickness.

A number of hardware-based and software-based strategies have been suggested to eliminate motion artifacts for improvement of 3D-optical coherence tomography (OCT) image quality. However, the hardware-based strategies have to employ additional hardware to record motion compensation information. Many software-based strategies have to need additional scanning for motion correction at the expense of longer acquisition time. To address this issue, we propose a motion artifacts correction and motion estimation method for OCT volumetric imaging of anterior segment, without requirements of additional hardware and redundant scanning. The motion correction effect with subpixel accuracy for in vivo 3D-OCT has been demonstrated in experiments. Moreover, the physiological information of imaging object, including respiratory curve and respiratory rate, has been experimentally extracted using the proposed method. The proposed method offers a powerful tool for scientific research and clinical diagnosis in ophthalmology and may be further extended for other biomedical volumetric imaging applications.

OBJECTIVE: To observe the morphological characteristics of posterior scleral staphyloma (PSS) with or without macular retinoschisis (MRS) using optical coherence tomography (OCT). Additionally, the incidence and severity of other pathologic myopic maculopathy associated with posterior scleral staphyloma was also evaluated.
METHODS: General information and OCT imaging data from 440 patients with posterior scleral staphyloma (PSS) and the PSS curvature > 20×10-3 μm-1 were collected. These patients visited the Department of Ophthalmology at the First Affiliated Hospital of Harbin Medical University from January 2013 to June 2021. The obtained OCT images of PSS were analyzed using the Image J software to measure the curvature along the Bruch\'s membrane. The measured curvature was divided into four levels using the quartile method. The classification of macular retinoschisis (MRS) was based on the anatomical structure of the retina and the location of macular retinoschisis. Patients with PSS accompanied by MRS were assigned to the MRS group, while PSS patients without MRS were assigned to the non-MRS group. Additionally, typical OCT changes in other pathologic myopic maculopathy diseases, such as myopic choroidal neovascularization (mCNV), myopic traction maculopathy (MTM), and myopic foveoschisis (MF), were recorded and evaluated.
RESULTS: A total of 615 eyes (328 right eyes, 287 left eyes) from 440 patients (80 males and 360 females) were recruited in this study. The MRS group consisted of 159 patients (36.1%) with 190 eyes (30.9%), while the non-MRS group consisted of 281 patients (63.9%) with 425 eyes (69.1%). Both groups had a significantly higher proportion of female patients compared to male patients, and the right eye was more commonly affected than the left eye. In the MRS group, the prevalence of MRS increased progressively with the severity of PSS. Among the common posterior pole diseases, epiretinal membrane had the highest prevalence (33.2%), while lamellar macular hole had the lowest prevalence (5.3%). In the non-MRS group, the proportion of PSS in each group decreased progressively (except for an equal prevalence in the third and fourth levels) with increasing severity of PSS. Among the common posterior pole diseases, choroidal neovascularization had the highest prevalence (41.4%), while lamellar macular hole had the lowest prevalence (6.5%). When comparing the two groups, there were no significant differences in age, gender, and eye distribution. The MRS group had a higher prevalence of macular schisis, retinal detachment, and dome-shaped macula (17.9%, 14.2%, 14.8%) compared to the non-MRS group (11.3%, 9.2%, 9.6%). The non-MRS group had a significantly higher prevalence of choroidal neovascularization (41.4%) compared to the MRS group (12.6%), while there were no significant differences in the prevalence of epiretinal membrane and lamellar macular hole between the two groups.
CONCLUSIONS: The prevalence of MRS increased progressively with the severity of PSS, and the MRS occurrence was positively correlated with PSS, which indicated that PSS may lead to MRS, while the proportion of PSS in each group decreases gradually with the severity of PSS in the non-MRS group decreased progressively (except for an equal prevalence in the third and fourth levels). In the MRS group, outer macular retinoschisiss were most relevant to posterior scleral staphyloma, and the prevalence of macular holes and retinal detachments was higher in the MRS group compared to the non-MRS group, indicating that MRS may further turn into complications such as macular holes and retinal detachments, which can significantly affect vision or lead to blindness. The prevalence of choroidal neovascularization (CNV) was significantly higher in the non-MRS group compared to the MRS group, suggesting that PSS with lower severity is more prone to develop into CNV. Dome-shaped macula (DSM) seems to play a protective role in the development of pathologic myopia, and abnormal changes in posterior scleral staphyloma curvature may be an important factor affecting the development and shape of DSM.

Radiographic examination has been an essential part of the diagnostic workflow in periodontology and implant dentistry. However, radiographic examination unavoidably involves ionizing radiation and its associated risks. Clinicians and researchers have invested considerable efforts in assessing the feasibility and capability of utilizing nonionizing imaging modalities to replace traditional radiographic imaging. Two such modalities have been extensively evaluated in clinical settings, namely, ultrasonography (USG) and magnetic resonance imaging (MRI). Another modality, optical coherence tomography (OCT), has been under investigation more recently. This review aims to provide an overview of the literature and summarize the usage of USG, MRI, and OCT in evaluating health and pathology of periodontal and peri-implant tissues. Clinical studies have shown that USG could accurately measure gingival height and crestal bone level, and classify furcation involvement. Due to physical constraints, USG may be more applicable to the buccal surfaces of the dentition even with an intra-oral probe. Clinical studies have also shown that MRI could visualize the degree of soft-tissue inflammation and osseous edema, the extent of bone loss at furcation involvement sites, and periodontal bone level. However, there was a lack of clinical studies on the evaluation of peri-implant tissues by MRI. Moreover, an MRI machine is very expensive, occupies much space, and requires more time than cone-beam computed tomography (CBCT) or intraoral radiographs to complete a scan. The feasibility of OCT to evaluate periodontal and peri-implant tissues remains to be elucidated, as there are only preclinical studies at the moment. A major shortcoming of OCT is that it may not reach the bottom of the periodontal pocket, particularly for inflammatory conditions, due to the absorption of near-infrared light by hemoglobin. Until future technological breakthroughs finally overcome the limitations of USG, MRI and OCT, the practical imaging modalities for routine diagnostics of periodontal and peri-implant tissues remain to be plain radiographs and CBCTs.

OBJECTIVE: To investigate the formation and absorption of avascular subretinal hyperreflective material (avSHRM) in neovascular age-related macular degeneration (nAMD) based on optical coherence tomography angiography (OCTA) characteristics.
METHODS: Prospective cohort study METHODS: This study included patients with treatment-naïve nAMD and followed up for 3 months. Subjects were classified into avSHRM group and non-avSHRM group based on the presence of avSHRM at baseline. Quantitative OCTA characteristics including explant area, perimeter, vessel area, density, length, junctions, endpoints, lacunarity, maximum vessel caliber, vessel dispersion, and fractal dimension were assessed, three-dimensional volume and optical density ratio (ODR) of avSHRM were measured. Comparison analyses, correlate coefficients and regression models were applied to explore factors associated with avSHRM formation and absorption.
RESULTS: 88 eyes from 88 patients (39 females) were enrolled. Compared to non-avSHRM group, avSHRM group exhibit a more intricate vasculature, characterized by higher value of macular neovascularization (MNV) perimeter, vessel area, total vessel length, total number of junctions and total number of endpoints (all P < 0.05), as well as the maximum vessel caliber (P < 0.001). In the multivariate model, which has been adjusted for age, gender, and types of medications, avSHRM absorption was correlated with baseline average vessel length, maximum vessel caliber and avSHRM ODR (standardized β = 0.274, -0.367 and -0.334; P = 0.049, 0.010 and 0.018, respectively), with an adjusted R² of 0.453.
CONCLUSIONS: Quantitative OCTA measurements can be utilized for assessing the dynamics of avSHRM in nAMD. Patients with more complex vasculature are at a higher risk of avSHRM formation. Average vessel length, maximum vessel diameter and avSHRM ODR play a role in its absorption.

In this study, we employed a method integrating optical coherence tomography (OCT) with the U-Net and Visual Geometry Group (VGG)-Net frameworks within a convolutional neural network for quantitative characterization of the three dimensional whole blood during the dynamic coagulation process. VGG-Net architecture for the identification of blood droplets across three distinct coagulation stages including drop, gelation, and coagulation achieves an accuracy of up to 99%. In addition, the U-Net architecture demonstrated proficiency in effectively segmenting uncoagulated and coagulated portions of whole blood, as well as the background. Notably, parameters such as volume of uncoagulated and coagulated segments of the whole blood were successfully employed for the precise quantification of the coagulation process, which indicates well for the potential of future clinical diagnostics and analyses.

Quantitative analysis of optical attenuation based on optical coherence tomography images will offer an effective method to enhance diagnostic capabilities. In this paper, the optical attenuation in demineralized caries specimens was calculated to distinguish between normal teeth and carious teeth and further to differentiate the severity of caries, and thus come to the half-automated diagnosis of dental caries. Results show that the attenuation coefficient in carious regions is approximately 4.97 mm - 1 ± 0.206 $$ 4.97\\ {\\mathrm{mm}}^{-1}\\left(\\pm 0.206\\right) $$ , while that of normal teeth is about 3.69 mm - 1 ± 0.231 $$ 3.69\\ {\\mathrm{mm}}^{-1}\\ \\left(\\pm 0.231\\right) $$ . Attenuation coefficient of carious regions is 35% higher than that of normal teeth. Moreover, five classes of caries were qualified and classified based on the optical attenuation coefficient. Compared with the healthy teeth, there is a noticeable disparity in the attenuation coefficients of carious teeth, both on the surface and at the dentinoenamel junction. This study provides a method for accurate caries diagnosis, particularly in detection of early lesions and subtle structural changes.

OBJECTIVE: To quantify the presence of early structural alterations in the outer retinal layer and choroid among healthy subjects and diabetic patients with no or mild diabetic retinopathy, and to establish the correlation between the measured structural parameters and retinal sensitivity.
METHODS: In total, 31 eyes from subjects with type 2 diabetes and 29 eyes from healthy subjects were enrolled. Optical coherence tomography was used to measure outer retina layers and choroid, while microperimetry was used to characterize the changes of visual function in a 6-mm diameter area at macula. Quantitative analysis of structural and functional changes was performed between groups and the structure-function correlations were determined.
RESULTS: The thickness of myoid and ellipsoid zone, choroid and the mean retinal sensitivity were significantly smaller in diabetic group than that in controls (all P values < 0.05). Besides, thinner choroid and outer retina was associated with the decreased retinal sensitivity，especially in diabetic patients (r = 0.377, P = 0.048; r = 0.401, P = 0.034; respectively). Final multiple regression models showed the outer retinal thickness (ORT) (P = 0.033), choroidal thickness (P = 0.003) and the interaction between ORT and choroidal thickness (P = 0.001) were significant predictors to retinal sensitivity.
CONCLUSIONS: Thinning of choroid and outer retina were significantly correlated with reduced retinal sensitivity, which indicate outer retina and choroid might be potential imaging markers for evaluation of visual function related to neural impairment in type 2 diabetic patients without or in the early stage of diabetic retinopathy.

The precise features of lesions in non-ST-segment elevation myocardial infarction (NSTEMI) patients with total occlusion (TO) of the infarct-related artery (IRA) are still unclear. This study employs optical coherence tomography (OCT) to investigate pathological features in NSTEMI patients with or without IRA TO and explores the relationship between thrombus types and IRA occlusive status. This was a single-center retrospective study. A total of 202 patients diagnosed with NSTEMI were divided into two groups: those with Thrombolysis In Myocardial Infarction (TIMI) flow grade 0 before percutaneous coronary intervention (PCI) (referred to as the TO group, n = 100) and those TIMI flow grade 1-3 (referred to as the Non-TO group, n = 102). Baseline characteristics, coronary angiography findings, and OCT results were collected. Multivariate logistic analysis identified factors influencing TO in NSTEMI. The category of NSTEMI was further subdivided based on the type of electrocardiogram (ECG) into two subgroups: ST segment unoffset myocardial infarction (STUMI) and ST segment depression myocardial infarction (STDMI). This division allows for a more specific classification of NSTEMI cases. The TO group had a younger age, higher male representation, more smokers, lower hypertension and cerebrovascular disease incidence, lower left ventricular ejection fraction (LVEF), and higher creatine kinase myocardial band (CKMB) and creatine kinase (CK) peak levels. In the TO group, LCX served as the main IRA (52.0%), whereas in the Non-TO group, LAD was the predominant IRA (45.1%). Compared to the Non-TO group, OCT findings demonstrated that red thrombus/mixed thrombus was more common in the TO group, along with a lower occurrence of white thrombus (p < 0.001). The TO group exhibited a higher prevalence of STUMI (p = 0.001), whereas STDMI was more commonly observed in the Non-TO group (p = 0.001). NSTEMI presents as STUMI and STDMI distinct entities. Red thrombus/mixed thrombus in IRA often indicates occlusive lesions with STUMI on ECG. White thrombus suggests non-occlusive lesions with STDMI on ECG.

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