Swept-source Optical Coherence Tomography Research Articles

Choroidal Vascularity and Axial Length Elongation in Highly Myopic Children: A 2-Year Longitudinal Investigation.

To examine the influence of subfoveal choroidal thickness (SFCT) and choroidal vascularity index (CVI) on axial length (AL) elongation over a 2-year period in highly myopic children. In this is prospective, longitudinal, observational study, 163 participants (74%), who were 8 to 18years of age with bilateral high myopia (sphere ≤ -6.0 D) and without pathologic myopia, completed follow-up visits over 2years. All participants underwent baseline and follow-up ocular examinations, including swept-source optical coherence tomography (SS-OCT) and AL measurements. SFCT and CVI were derived from SS-OCT scans using a deep-learning-based program for choroidal structure assessment. The mean age of the participants at baseline was 15.0years (±2.3), with males constituting 47% of the cohort. An inverse relationship was observed between AL elongation and increases in baseline age, baseline SFCT, and CVI, as well as a decrease in baseline AL. Adjusting for other factors, every 10-µm increase in SFCT and each 1% increase in CVI were associated with decreases in AL elongation of 0.007mm (95% confidence interval [CI], -0.013 to -0.002; P = 0.011) and 0.010mm (95% CI, -0.019 to 0.000; P = 0.050), respectively. The incorporation of SFCT or CVI into predictive models improved discrimination over models using only age, gender, and baseline AL (both P < 0.05, likelihood ratio test). Our findings suggest a possible association between a thinner choroid and increased AL elongation over 2 years in children with high myopia, after adjusting for potential baseline risk factors such as age, gender, and initial AL.

Accuracy of intraocular lens calculation formulas based on swept-source OCT biometer in cataract patients with phakic intraocular lens

PurposeTo research the accuracy of intraocular lens (IOL) calculation formulas and investigate the effect of anterior chamber depth (ACD) and lens thickness (LT) measured by swept-source optical coherence tomography biometer (IOLMaster 700) in patients with posterior chamber phakic IOL (PC-pIOL).MethodsRetrospective case series. The IOLMaster 700 biometer was used to measure axial length (AL) and anterior segment parameters. The traditional formulas (SRK/T, Holladay 1 and Haigis) with or without Wang-Koch (WK) AL adjustment, and new-generation formulas (Barret Universal II [BUII], Emmetropia Verifying Optical [EVO] v2.0, Kane, Pearl-DGS) were utilized in IOL power calculation.ResultsThis study enrolled 24 eyes of 24 patients undergoing combined PC-pIOL removal and cataract surgery at Xiamen Eye Center of Xiamen University, Xiamen, Fujian, China. The median absolute prediction error in ascending order was EVO 2.0 (0.33), Kane (0.35), SRK/T-WKmodified (0.42), Holladay 1-WKmodified (0.44), Haigis-WKC1 (0.46), Pearl-DGS (0.47), BUII (0.58), Haigis (0.75), SRK/T (0.79), and Holladay 1 (1.32). The root-mean-square absolute error in ascending order was Haigis-WKC1 (0.591), Holladay 1-WKmodified (0.622), SRK/T-WKmodified (0.623), EVO (0.673), Kane (0.678), Pearl-DGS (0.753), BUII (0.863), Haigis (1.061), SRK/T (1.188), and Holladay 1 (1.513). A detailed analysis of ACD and LT measurement error revealed negligible impact on refractive outcomes in BUII and EVO 2.0 when these parameters were incorporated or omitted in the formula calculation.ConclusionThe Kane, EVO 2.0, and traditional formulas with WK AL adjustment displayed high prediction accuracy. Furthermore, the ACD and LT measurement error does not exert a significant influence on the accuracy of IOL power calculation formulas in highly myopic eyes implanted with PC-pIOL.

Anatomic Features of the Lamina Cribrosa and Optic Disc in Ocular Hypertension, Glaucoma and Healthy Eyes.

Central lamina cribrosa thickness (LCT) was found to be higher in eyes with ocular hypertension (OHT) compared with primary open angle glaucoma (POAG) and healthy controls (HCs). To evaluate the anatomic features of lamina cribrosa (LC) and the optic disc (OD) using swept-source optical coherence tomography (OCT) in eyes with OHT. Treatment naive eyes with OHT and POAG and healthy eyes were included. All eyes underwent a complete ophthalmological examination in addition to swept-source OCT of the OD. Anatomic features of LC, including central LCT, LC depth, prelaminar depth (PLD), and prelaminar tissue thickness, were measured manually using the internal caliper function of the OCT device and compared within groups. OD ovality, disc-foveal angle, and OD torsion were measured on colored photographs, using imageJ software. Seventy-one eyes of 37 patients in the OHT group, 41 eyes of 26 patients in the POAG group, and 30 eyes of 30 patients in the HC group were enrolled in the study. Groups were similar in age and sex distribution. Central LCT was significantly higher in the OHT group, compared with HCs (333.8 ± 50.5 vs 304.5 ± 46.3 µm, P = 0.02) and POAG group (286.7 ± 140.4, P = 0.001). PLD and LC depth were both highest in POAG (282.3 ± 145.5 µm and 471.3 ± 195.2 µm), followed by OHT (244.8 ± 30.2 µm and 440.7 ± 18.7 µm) and HCs (170.1 ± 152.6 µm and 412.8 ± 80 µm), only the difference between POAG and HCs in PLD was statistically significant ( P = 0.03). Prelaminar tissue thickness, OD torsion, disc-foveal angle, and disc ovality showed no significant difference. LC was significantly thicker in eyes with OHT, compared with POAG and HCs. This finding may be relevant to optic nerve protection from high intraocular pressure in patients with OHT.

Degree of conversion and interfacial adaptation of touch-cure resin cement polymerized by self-curing or dual-curing with reduced light.

The first aim of this study was to determine whether there is a difference in degree of conversion (DC) of touch-cure cements polymerized by self-curing with adhesive or dual-curing under reduced light. The second aim was to compare interfacial adaptation of zirconia restoration cemented using touch-cure cements self-cured or dual-cured by reduced light. The DC of touch-cure resin cements with adhesive was measured continuously using Fourier transform infrared spectrometry. Experimental groups differed depending on touch-cure cement. Each group had three subgroups of polymerization method. For subgroup 1, the DC was measured by self-curing. For subgroups 2 and 3, the DCs were measured by dual-curing with reduced light penetrating 3mm and 1mm zirconia blocks, respectively. For interfacial adaptation evaluation, Class I cavity was prepared on an extracted third molar, and zirconia restoration was fabricated. The restoration was cemented using the same cement. Groups and subgroups for interfacial adaptation were the same as those of the DC measurement. After thermo-cycling, interfacial adaptation at the tooth-restoration interface was evaluated using swept-source optical coherence tomography imaging. The DC of touch-cure cement differed depending on the measurement time, resin cement, and polymerization method (p < 0.05). Interfacial adaptation was different depending on the resin cement and polymerization method (p < 0.05). For touch-cure cement, light-curing with higher irradiance presented a higher DC and superior interfacial adaptation than light-curing with lower irradiance or self-curing. Although some adhesives accelerate the self-curing of touch-cure cement, light-curing for touch-cure cement is necessary for zirconia cementation.

Influence of Carotid Artery Stenting on the Retina and Choroid.

The effect of carotid artery stenting in patients with unilateral carotid artery stenosis on the retina and choroid was evaluated using swept-source optical coherence tomography angiography (SS-OCTA). SS-OCTA examination was conducted before stenting and 4days and 3months after stenting. The retinal nerve fiber layer, ganglion cell-inner plexiform layer (GCIPL), inner nuclear layer, superficial vascular complex (SVC), deep vascular complex (DVC), choroidal vascular volume (CVV), and choroidal vascular index were measured. Repeated-measures analysis of variance was performed to assess the impact of carotid artery stenting on optical coherence tomography angiography (OCTA) metrics. At baseline, 303 eyes from 160 patients (61.82 ± 9.98years; 85.29% males) were enrolled. SVC and DVC densities and CVV were lower in ipsilateral eyes (stenosed side) compared to contralateral eyes (all P < 0.05). Four days after stenting, a significant increase was seen in SVC density in ipsilateral eyes (P < 0.05) while a significant increase was seen in CVV in ipsilateral eyes and contralateral eyes (both P < 0.05). Three months after stenting (63 patients with 114 eyes), a significant decrease was seen in the GCIPL thickness of ipsilateral and contralateral eyes (all P < 0.001). Short term after carotid artery stenting, ipsilateral eyes showed a rapid and significant increase in SVC density and CVV. Optical coherence tomography (OCT)/OCTA measurements may have the potential to detect retinal and choroidal changes after stenting. Future research on the long-term effect of stenting on the retina and choroid will be guided by these findings.

Peripheral Ganglion Cell Complex Thickness and Retinal Microvasculature in Myopia Using Wide-Field Swept-Source OCT.

This study aims to investigate the impact of axial elongation on ganglion cell complex thickness (GCCT) and retinal capillary density (CD) using wide-field swept-source optical coherence tomography angiography. A retrospective cross-sectional analysis was conducted involving 506 eyes. Fovea-centered scans were obtained to assess the subregional GCCT and capillary density across the whole retina, the superficial capillary plexus (SCP), and deep capillary plexus (DCP) among three groups: normal control, high myopia (HM) eyes with axial length < 28mm, and HM eyes with axial length > 28mm. Regional variations (central vs. peripheral, quadrants difference [superior, inferior, nasal, and temporal]) were analyzed. In HM eyes with axial length > 28mm, GCCT and retinal CD exhibit a general decline in most regions (P < 0.05). In HM eyes with axial length < 28mm, significant reductions were observed specifically in peripheral regions, as in the GCCT beyond the 3 × 3mm2 area and CD in the 9-12mm whole retina, 9-12mm superior SCP, and 6-12mm DCP (P < 0.05). Maximum GCCT and retinal CD reduction with axial elongation was observed in subregions beyond 6 × 6 mm2. GCCT beyond the 3 × 3 mm2 area and peripheral retinal CD beyond the 6 × 6 mm2 area were more susceptible to axial elongation and are thereby deserving of particular attention. It is necessary to evaluate different regions during the clinical assessment of the effect of myopia on the fundus and pay close attention to the peripheral retina.

Treatment of dry eyes with lifitegrast 5% before cataract surgery: A prospective trial

Abstract Objective: The objective of the study was to evaluate the impact of dry eye treatment on intraocular lens (IOL) biometry measurements and postoperative refractive outcome. Design: This study involves a prospective interventional study. Participants: Consecutive patients with dry eye disease undergoing cataract surgery were included in the study. Materials and Methods: All participants underwent a comprehensive dry eye assessment including the ocular surface disease index (OSDI) questionnaire, Schirmer’s test without anesthesia, corneal fluorescein staining, and conjunctival lissamine green staining. Optical biometry was performed using swept-source optical coherence tomography (IOL Master® 700, Zeiss), and corneal aberrometry was measured using a scanning-slit aberrometer (OPD SCAN III, Nidek). Diagnosis of dry eye was made according to Dry Eye Workshop II. Patients received 6 weeks of treatment of lifitegrast 5% and preservative-free artificial tear eye drops and had repeat testing at the end of 6 weeks. The change in subjective and objective dry eye tests and biometry measurements and the difference in target and postoperative refraction before and after treatment were compared. Results: Forty eyes of 21 patients were included in the study. Subjectively, OSDI improved from 26.35 ± 6.24 at baseline to 20.97 ± 8.41 after treatment (P = 0.03). Objectively, corneal staining improved from 1.42 ± 1.78 at baseline to 0.39 ± 0.67 after treatment (P = 0.006). No changes were observed in Schirmer’s test without anesthesia, conjunctival staining, or corneal aberrometry (P &gt; 0.05). Repeated biometry after dry eye treatment showed a change in IOL power difference ≥0.5 diopters in 50% (20) of eyes. Mean absolute error was within 0.25D in 87.5% (35) of eyes after treatment compared to 67.5% at baseline (P = 0.05). Conclusion: Dry eye treatment leads to subjective symptom improvement and changes in IOL power calculations and postoperative refractive outcomes. Assessing and treating patients for dry eyes before cataract surgery is important in maximizing refractive outcomes.

Impact and Correction of an Anterior Phakic Intraocular Lens on Swept-Source Optical Coherence Tomography Biometry.

To evaluate the impact of anterior chamber phakic intraocular lens (pIOL) on swept-source optical coherence tomography (SS-OCT) biometric measurements and IOL power calculation. This retrospective analysis of 67 eyes of 49 patients with previous anterior chamber pIOL implantation analyzed the accuracy of automatic segmentation of the anterior surface of the crystalline lens and its impact on anterior chamber depth (ACD, measured from epithelium to lens), lens thickness measurements, and IOL power calculation. The sample was divided into two groups: correct detection of the anterior surface of the crystalline lens and inaccurate detection. Segmentation of eyes from the inaccurate detection group was manually corrected and ACD and lens thickness were calculated using ImageJ software. IOL power was calculated using 7 formulas for both measurements. The anterior surface of the crystalline lens was mis-identified in 13 (19.4%) eyes. ACD was underestimated (Δ -0.85 ± 0.33 mm, P < .001) and lens thickness was overestimated (Δ +0.81 ± 0.25 mm, P < .001). Manual correction changed the target spherical equivalent only in the Haigis formula (P = .009). After correction for segmentation bias, the Pearl DGS, Cooke K6, and EVO 2.0 formulas showed the lowest prediction error, with the Pearl DGS showing greatest accuracy within ±1.00 diopters of prediction error range (81.0%). SS-OCT biometry misidentifies the anterior surface of the crystalline lens in a significant proportion, resulting in significant IOL power calculation error in the Haigis formula. Manual proofing of segmentation is mandatory in every patient with anterior chamber pIOL implantation. After correct segmentation, the Pearl DGS, Cooke K6, and EVO seem to be the best formulas. [J Refract Surg. 2024;40(8):e562-e568.].

Optical coherence tomography angiography evaluation of retinal and choroidal microvascular changes in pregnant women with a history of unexplained recurrent spontaneous abortions.

To study retinal and choroidal microcirculation by optical coherence tomography angiography (OCTA) in pregnant women with unexplained recurrent spontaneous abortion (RSA) and to compare them with healthy pregnant and nonpregnant subjects. Pregnant women with an unexplained history of RSA (group 1), healthy pregnant (group 2), and healthy non-pregnant women (group 3) were included in the study. After a thorough ophthalmologic examination:best-corrected visual acuity, intraocular pressure,slit-lamp biomicroscopy, fundus examination,autorefractometer, biometry, and axial length measurement; OCT and OCTA measurements were performed with Swept Source OCT-Angiography (Topcon Co, Japan). The nonpregnant group had higher values for central foveal superficial capillary plexus (SCP) and deep capillary plexus (DCP) vessel density (VD) and lower values for superior, inferior, and mean VD compared with pregnant groups (p < 0.001). Choriocapillaris values (CC) VD were higher in groups 1 and 2 than in group 3 (p < 0.001). The group with unexplained RSA had a relatively smaller FAZ (foveal avascular zone) area than the group of healthy pregnant women (p:0.047). There were no statistically significant differences between groups in the retina, retinal nerve fiber layer, ganglion cell layer, and choroidal thickness (p > 0.05). Although our study did not identify any etiology in pregnant women with RSA, we observed detectable differences in FAZ area and vessel density values using OCTA, when comparing them with healthy pregnant women and healthy nonpregnant controls. We believe that OCTA, as used in many pathologies such as diabetic and hypertensive retinopathy and retinal vascular occlusion, can also be extended to unexplained RSA both to detect etiology and to monitor treatment in studies with a larger number of patients.

Optical Assessment of Photoreceptor Function Over the Macula.

The purpose of this study was to develop next-generation functional photoreceptor imaging using ultrahigh-speed swept-source optical coherence tomography (UHS-SS-OCT) and split-spectrum amplitude-decorrelation optoretinography (SSADOR) algorithm. The advancement enables rapid surveying of large retinal areas, promising non-contact, objective, and quantifiable measurements of macular visual function. We designed and built a UHS-SS-OCT prototype instrument using a wavelength tunable laser with 1 MHz A-scan rate. The functional scanning protocol records 5 repeated volumes in 3 seconds. A flash pattern selectively exposes the imaged retina area. SSADOR quantifies photoreceptor light response by extracting optical coherence tomography (OCT) signal changes within the photoreceptor outer segment before and after the flash. The study prospectively enrolled 16 eyes from 8 subjects, demonstrating the ability to measure photoreceptor light response over a record field of view (3 × 3mm2) with high topographical resolution (approximately 100 µm). The measured SSADOR signal corresponds to the flashed pattern, whose amplitude also correlates with flash strength, showing consistency and reproducibility across subjects. The integration of high-performance UHS-SS-OCT and SSADOR enables characterizing photoreceptor function over a clinically meaningful field of view, while maintaining a workflow that can be integrated into routine clinical tests and trials. The new approach allows detecting changes in photoreceptor light response with high sensitivity and can detect small focal impairments. This innovative advance can enable us to detect early photoreceptor abnormalities, as well as help to stage and monitor degenerative retinal diseases, potentially providing a surrogate visual function marker for retinal diseases and accelerating therapeutic development through a safe and efficient outcome endpoint.

Dispersion-Tuned Mode-Locked Laser for Swept Source OCT at 850 nm Using a cFBG and the Pulse Modulation Technique

Dispersion-Tuned Mode-Locked Laser for Swept Source OCT at 850 nm Using a cFBG and the Pulse Modulation Technique

Comparison of Scheimpflug Imaging (Pentacam HR) and Swept-Source Optical Coherence Tomography (CASIA2) in Eyes With Macular Corneal Dystrophy.

Assessment of tomographic characteristics and interdevice comparability between Scheimpflug imaging (Pentacam HR, Oculus Optikgeräte GmbH, Wetzlar, Germany) and swept-source optical coherence tomography (CASIA2, Tomey Corp., Nagoya, Japan) in eyes with macular corneal dystrophy (MCD). Eyes with MCD were examined by Pentacam HR and CASIA2. Interdevice comparison was performed using a Wilcoxon matched pairs test and Bland-Altman plots with 95% limit of agreement. A Spearman rank correlation coefficient was used for correlating indices of both devices. This retrospective study included 31 eyes of 18 patients (mean age: 32.1 ± 10.7 years). Eyes with MCD demonstrated a moderate astigmatism with a Cylinder anterior of 2.56 ± 1.50 D (Pentacam HR) and 2.52 ± 1.57 D (CASIA2) without a difference between both devices. CASIA2 (0.34 ± 0.14 D) measured lower values of Cylinder posterior compared with Pentacam HR (0.96 ± 0.66 D) (P < 0.0001). Comparison of pachymetry (Pentacam HR vs. CASIA2) showed higher values of the central corneal thickness (619 ± 227 μm vs. 445 ± 67 μm, P = 0.0001) and the thinnest corneal thickness (499 ± 165 μm vs. 430 ± 60 μm, P = 0.0167) for Pentacam HR. Corneal densitometry measurement revealed that increasing gray scale units caused a greater interdevice difference for pachymetry values, as Pentacam HR measured higher than CASIA2 for more opaque corneas. Eyes with MCD tend to have thinner corneas and a higher amount of corneal astigmatism than healthy eyes. In advanced MCD, Scheimpflug technology may mistakenly overestimate corneal thickness. The pachymetry measurement of the optical coherence tomography should be used when planning corneal surgery such as excimer laser-assisted phototherapeutic keratectomy to determine the ablation depth.

Adaptive contour-tracking to aid wide-field swept-source optical coherence tomography imaging of large objects with uneven surface topology.

High-speed and wide-field optical coherence tomography (OCT) imaging is increasingly essential for clinical applications yet faces challenges due to its inherent sensitivity roll-off and limited depth of focus, particularly when imaging samples with significant variations in surface contour. Here, we propose one innovative solution of adaptive contour tracking and scanning methods to address these challenges. The strategy integrates an electrically tunable lens and adjustable optical delay line control with real-time surface contour information, enabling dynamic optimization of imaging protocols. It rapidly pre-scans the sample surface to acquire a comprehensive contour map. Using this map, it generates a tailored scanning protocol by partitioning the entire system ranging distance into depth-resolved segments determined by the optical Raleigh length of the objective lens, ensuring optimal imaging at each segment. Employing short-range imaging mode along the sample contour minimizes data storage and post-processing requirements, while adaptive adjustment of focal length and reference optical delay line maintains high imaging quality throughout. Experimental demonstrations show the effectiveness of the adaptive contour tracking OCT in maintaining high contrast and signal-to-noise ratio across the entire field of view, even in samples with significantly uneven surface curvatures. Notably, this approach achieves these results with reduced data volume compared to traditional OCT methods. This advancement holds promise for enhancing OCT imaging in clinical settings, particularly in applications requiring rapid, wide-field imaging of tissue structures and blood flow.

Swept-source optical coherence tomography early findings in patients with carotid artery disease.

Ocular ischemic syndrome can be the first and only hint of life-threatening carotid artery disease. The early recognition of carotid stenosis-related retinal signs, as well as the comprehension of the pathophysiology behind retinal changes could become relevant for physicians to predict the risk of stroke. The aim of this study is to assess the carotid artery disease-induced early structural retinochoroidal changes by means of swept-source optical coherence tomography (SS-OCT). A prospective observational study was conducted in 72 eyes with carotid stenosis. According to the degree of stenosis, the participants were divided into a normal group (34 eyes), a mild-moderate stenosis group (22 eyes), a severe stenosis group (16 eyes). SS-OCT and OCTA were performed to scan macular fovea. Central macular thickness (CMT), subfoveal choroidal thickness (SCT) and foveal avascular zona (FAZ) area were the major measurements for our study. CMT was significantly thicker in group 3 when compared to group 2 and 1. SCT was significantly thinner in group 3 vs group 1, being thicker in group 2 when compared to group 1. No significant differences were obtained when comparing FAZ in the superficial and middle capillary plexus although it was significant when comparing the FAZ in the deep capillary plexus between group 1 and 3. internal carotid artery stenosis greater than 70% leads to a significant increase in CMT and a decrease in SCT prior the development of clinical findings of ocular ischemia syndrome.

Estimating Uncertainty of Geographic Atrophy Segmentations with Bayesian Deep Learning

To apply methods for quantifying uncertainty of deep learning segmentation of geographic atrophy (GA). Retrospective analysis of OCT images and model comparison. One hundred twenty-six eyes from 87 participants with GA in the SWAGGER cohort of the Nonexudative Age-Related Macular Degeneration Imaged with Swept-Source OCT (SS-OCT) study. The manual segmentations of GA lesions were conducted on structural subretinal pigment epithelium en face images from the SS-OCT images. Models were developed for 2 approximate Bayesian deep learning techniques, Monte Carlo dropout and ensemble, to assess the uncertainty of GA semantic segmentation and compared to a traditional deep learning model. Model performance (Dice score) was compared. Uncertainty was calculated using the formula for Shannon Entropy. The output of both Bayesian technique models showed a greater number of pixels with high entropy than the standard model. Dice scores for the Monte Carlo dropout method (0.90, 95% confidence interval 0.87-0.93) and the ensemble method (0.88, 95% confidence interval 0.85-0.91) were significantly higher (P<0.001) than for the traditional model (0.82, 95% confidence interval 0.78-0.86). Quantifying the uncertainty in a prediction of GA may improve trustworthiness of the models and aid clinicians in decision-making. The Bayesian deep learning techniques generated pixel-wise estimates of model uncertainty for segmentation, while also improving model performance compared with traditionally trained deep learning models. Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Association of SDF-1-3' Gene A Variant with Diabetic Retinopathy in the Hungarian Population.

We investigated the association between the SDF-1-3' (c801G > A) variant and the development of diabetic macular edema (DME) or proliferative diabetic retinopathy (PDR) in a Hungarian cohort. SDF-1-3' (c801G > A) was genotyped in 103 patients with diabetic retinopathy and 31 age- and sex-matched non-diabetic controls. Central retinal and choroidal thickness was measured by swept-source optical coherence tomography. The distribution of heterozygous and homozygous SDF-1-3' (c801G > A) genotypes was similar in diabetic and control subjects. The SDF-3'(c801AA) genotype was associated with DME (n = 94 eyes, allele distribution p = 0.006, genotype distribution p = 0.01 OR: 2.48, 95% CL: 1.21-5.08) in both univariable and multivariable modelling, independent of duration and type of diabetes, HbA1C, hypertension and microalbuminuria (p = 0.03). DME occurred earlier in patients carrying the SDF-1 (c801A) allele (Kaplan-Meier analysis, log-rank test p = 0.02). A marginally significant association was found between the presence of the SDF-1 (c801A) allele and the development of PDR (n = 89 eyes, p = 0.06). The SDF-1-3' (c801A) allele also showed a correlation with central retinal (p = 0.006) and choroidal (p = 0.08) thickness. SDF-1-3' (c801G > A) is involved in the development of macular complications in DM independent of critical clinical factors, suggesting that SDF-1 may be a future therapeutic target for high-risk patients, especially those carrying the SDF-1 (c801A) allele.

OCTA quantitative assessment of exercise-induced variations and recovery in retinal microvasculature of healthy subjects with or without masks

PurposeTo investigate the impact of exercise and mask-wearing on retinal microvasculature using optical coherence tomography angiography (OCTA). MethodsA total of 30 healthy volunteers were enrolled and tasked with physical exercise to reach 75–80 % maximum heart rates. Swept-source OCTA was performed on the macular region and optic nerve head (ONH) in participants with no mask, surgical mask, or N95 mask at quiescent conditions (Step 1) and 0 min, 10 min, 20 min, and 30 min post-exercise (Steps 2–5, respectively). The functional vessel density (VD), including the superficial and deep plex (SP and DP) in the macular area and the superficial plex (SP), nerve fiber plex, and small vessels in the optic nerve head, were measured. ResultsUnder quiescent conditions, the functional VD of SP and DP exhibited significant reduction with surgical and N95 masks in the foveal area (P < 0.05). In step 2 (immediately after training) with or without masks, functional VD of SP and nerve fiber both showed significant reduction in the inside disc and peripapillary area, small functional VD of nerve fiber in the ONH showed significant reduction in peripapillary area (P < 0.05). These changes had been recovered in Step 5 (30 min post-exercise) in all groups (no-mask, surgical mask and N95 mask groups) (P > 0.05). ConclusionsMask-wearing and physical exercise reduce retinal functional VD in macular and ONH areas. The retinal vasoconstriction induced by exercise tends to recover after rest for approximately 30 min. Our research provides insights into mask-wearing and physical exercise's immediate retinal microvasculature effects, hinting at systemic microvascular changes.

GPU-accelerated OCT imaging: Real-time data processing and artifact suppression for enhanced monitoring of 3D bioprinted tissues and vascular-like networks

Optical coherence tomography (OCT) imaging technology has significant advantages in in situ and noninvasive monitoring of biological tissues. However, it still faces the following challenges: including data processing speed, image quality, and improvements in three-dimensional (3D) visualization effects. OCT technology, especially functional imaging techniques like optical coherence tomography angiography (OCTA), requires a long acquisition time and a large data size. Despite the substantial increase in the acquisition speed of swept source optical coherence tomography (SS-OCT), it still poses significant challenges for data processing. Additionally, during in situ acquisition, image artifacts resulting from interface reflections or strong reflections from biological tissues and culturing containers present obstacles to data visualization and further analysis. Firstly, a customized frequency domain filter with anti-banding suppression parameters was designed to suppress artifact noises. Then, this study proposed a graphics processing unit (GPU)-based real-time data processing pipeline for SS-OCT, achieving a measured line-process rate of 800[Formula: see text]kHz for 3D fast and high-quality data visualization. Furthermore, a GPU-based real-time data processing for CC-OCTA was integrated to acquire dynamic information. Moreover, a vascular-like network chip was prepared using extrusion-based 3D printing and sacrificial materials, with sacrificial material being printed at the desired vascular network locations and then removed to form the vascular-like network. OCTA imaging technology was used to monitor the progression of sacrificial material removal and vascular-like network formation. Therefore, GPU-based OCT enables real-time processing and visualization with artifact suppression, making it particularly suitable for in situ noninvasive longitudinal monitoring of 3D bioprinting tissue and vascular-like networks in microfluidic chips.

Polarization-resolved analysis of outer retinal bands: investigating ballistic and multiply scattered photons using full-field swept-source optical coherence tomography.

Precise interpretation of the anatomical origins of outer retinal optical coherence tomography (OCT) presents technical challenges owing to the delicate nature of the retina. To address this challenge, our study introduces a novel polarization-sensitive full-field swept-source OCT (FF-SS-OCT) that provides parallel-polarization and cross-polarization OCT measurements, predominantly capturing ballistically reflected photons and multiply scattered photons, respectively. Notably, parallel-polarization OCT unveils layer-like structures more effectively, including the inner plexiform layer (IPL) sub-layers, outer plexiform layer (OPL) sub-layers (in rod-dominant regions), and rod/cone outer segment (OS) tips, compared to cross-polarization OCT, where such sub-layers are not visible. Through a comparative analysis of parallel-polarization and cross-polarization OCT images of the outer retina, we discovered that the 2nd outer retinal OCT band results from contributions from both the ellipsoid zone (EZ) and the inner segment/outer segment (IS/OS) junction. Similarly, the 3rd outer retinal OCT band appears to reflect contributions from both the interdigitation zone (IZ) and photoreceptor OS tips. This polarization-sensitive approach advances our understanding of the origins of outer retinal OCT signals and proposes potential new biomarkers for assessing retinal health and diseases.

The Influence of Corneal Thickness on Surgically Induced Corneal Astigmatism Derived from Total Keratometry Measured by Anterior Segment Swept-Source OCT.

The purposeof the study was to explore the possible correlations between the anterior segment parameters derived from anterior segment swept-source optical coherence tomography (AS-SS-OCT) with the surgically induced corneal astigmatism (CSIA) calculated from total keratometry (TK) measured by AS-SS-OCT. Seventy-one eyes of 67 patients with age-related cataract who underwent phacoemulsification combined with intraocular lens implantation with 2.2-mm incision were included. The CSIA values were calculated from anterior keratometry (CSIAKant) and TK (CSIATK) measured by AS-SS-OCT, respectively. Hotelling's T2 test was used to evaluate the difference. The correlation of CSIA with various parameters derived from AS-SS-OCT was tested with the Spearman correlation coefficient. The centroid of CSIAKant and of CSIATK were 0.31 ± 0.55 D @ 54° and 0.41 ± 0.59 D @ 51°, with no significant difference (F = 1.283, p = 0.281, Hotelling's T2). The mean absolute CSIAKant and CSIATK were 0.58 ± 0.24 D and 0.65 ± 0.28 D. Spearman test showed that the magnitude of CSIAKant was negatively correlated with preoperative peripheral corneal thickness (PCT, p = 0.045) and the magnitude of anterior keratometry (p = 0.044). The magnitude of CSIATK was negatively correlated with preoperative central corneal thickness (CCT, p = 0.003) and preoperative PCT (p = 0.015). The increased thickness of the peripheral cornea is correlated with the decrease in the magnitude of the CSIA. The correlation we identified between the corneal thickness and the CSIA indicated that certain preoperative parameters should be considered for the prediction of CSIA for a more precise refractive outcome.