Retinal Pigment Epithelium Layer Research Articles

Automatic segmentation of hyperreflective dots via focal priors and visual saliency.

Hyperreflective dots (HRDs) can be observed in spectral domain optical coherence tomography (SD-OCT), which can provide a sensitive marker in the treatment decision process. Quantitative analyses of HRDs are the key to make appropriate decisions on observation, treatment, and retreatment. The purpose of this study is to automatically and accurately segment HRDs in SD-OCT B-scans with diabetic retinopathy (DR). The authors propose an automatic segmentation algorithm of HRDs via focal priors and visual saliency. The algorithm is divided into three stages: segmentation of retinal layers, calculation of the multiscale local contrast saliency map, and adaptive threshold segmentation. First, a method based on improved graph search is used to segment retinal layers to obtain the region of interest (ROI) and the reflectivity estimation of the retinal pigment epithelium (RPE) layer; then, the multiscale local contrast saliency map is obtained by using a local contrast measure, which measures the dissimilarity between the current pixels and corresponding neighborhoods; finally, an adaptive threshold is applied to segment HRDs. Experimental results on 20 SD-OCT B-scans demonstrate that our method is effective for HRDs segmentation. The average dice similarity coefficient (DSC) and detection accuracy are 71.12% and 85.07%, respectively. The proposed method can accurately segment HRDs in SD-OCT B-scans with DR and outperforms current state-of-the-art methods. Our method can provide reliable HRDs segmentation to assist ophthalmologists in clinical diagnosis, treatment, disease monitoring, andprogression.

Exploration of fluoroquinolone-induced retinal pigment epithelium layer changes in the pathogenesis of macular degeneration

PurposeFluoroquinolone toxicity studies in animals (cats, rabbits and mice) showed that acute retinal degenerations appear clinically related to phototoxicity. The aim of this study was to evaluate the association between the administration of oral fluoroquinolone and the onset of clinically or subclinically detectable acute retinal degeneration in humans. Material and MethodsThis study included patients that received oral fluoroquinolone treatment (ciprofloxacin, levofloxacin or moxifloxacin) for variable systemic diseases diagnosed by the Department of Urology and Infectious Diseases (study group, n=76), and age and sex matched otherwise healthy subjects (control group, n=50). All the subjects underwent a detailed ophthalmologic examination including tests for visual acuity, intraocular pressures, color vision, photostress recovery time and contrast sensitivity measurements, central foveal thickness, subfoveal choroidal thickness, ganglion cell complex thickness and 10/2 Humphrey visual field test. Color fundus and fundus autofluorescence photographs were also obtained. Examinations and tests were repeated at 1st week and 1st month in the study group. ResultsThere was no statistically significant difference among visual acuity, intraocular pressure, photostress recovery time, color vision, contrast sensitivity measurements, central foveal thickness, subfoveal choroidal thickness, average ganglion cell complex thickness, superior ganglion cell complex thickness, inferior ganglion cell complex thickness, focal loss volume, global loss volume, mean deviation, pattern standard deviation values in treatment group at baseline, 1st week and 1st month (p > 0.05, for the comparison of each parameters). There was not any alteration among color fundus and fundus autofluorescence photographs obtained at baseline, 1st week and 1st month in treatment group. All parameters within the study and control groups were similar throughout the study period (p > 0.05, for the comparison of each parameter). ConclusionThis study evaluated the association between the administration of oral fluoroquinolone and the onset of acute retinal degeneration. Preliminary results of this study showed that use of oral fluoroquinolone had no detectable impact on retinal degeneration at acute phase.

NURR1 expression regulates retinal pigment epithelial–mesenchymal transition and age-related macular degeneration phenotypes

Phenotypic variations in the retinal pigment epithelial (RPE) layer are often a predecessor and driver of ocular degenerative diseases, such as age-related macular degeneration (AMD), the leading cause of vision loss in the elderly. We previously identified the orphan nuclear receptor-related 1 (NURR1), from a nuclear receptor atlas of human RPE cells, as a candidate transcription factor potentially involved in AMD development and progression. In the present study we characterized the expression of NURR1 as a function of age in RPE cells harvested from human donor eyes and in donor tissue from AMD patients. Mechanistically, we found an age-dependent shift in NURR1 dimerization from NURR1-RXRα heterodimers toward NURR1-NURR1 homodimers in primary human RPE cells. Additionally, overexpression and activation of NURR1 attenuated TNF-α-induced epithelial-to-mesenchymal transition (EMT) and migration, and modulated EMT-associated gene and protein expression in human RPE cells independent of age. In vivo, oral administration of IP7e, a potent NURR1 activator, ameliorated EMT in an experimental model of wet AMD and improved retinal function in a mouse model that presents with dry AMD features, impacting AMD phenotype, structure, and function of RPE cells, inhibiting accumulation of immune cells, and diminishing lipid accumulation. These results provide insight into the mechanisms of action of NURR1 in the aging eye, and demonstrate that the relative expression levels and activity of NURR1 is critical for both physiological and pathological functions of human RPE cells through RXRα-dependent regulation, and that targeting NURR1 may have therapeutic potential for AMD by modulating EMT, inflammation, and lipid homeostasis.

Waardenburg syndrome type 4 coexisting with open-angle glaucoma: a case report

BackgroundWaardenburg syndrome is an autosomal dominant disorder with varying degrees of sensorineural hearing loss as well as abnormal pigmentation in hair, skin, and iris. There are four types of Waardenburg syndrome (1–4) with different characteristics. Mutations in six genes have been identified to be associated with the various types. Herein, we describe a case of Waardenburg syndrome type 4 combined with open-angle glaucoma.Case presentationA 43-year-old Han Chinese man had undergone trabeculectomy due to progression of visual field impairment and unstable intraocular pressure in both eyes. Slit-lamp examination revealed diffuse iris hypopigmentation in the left eye and hypopigmentation of part of the iris in the right eye. Fundus examination showed red, sunset-like fundus due to a lack of pigmentation in the retinal pigment epithelium layer, diffuse loss of the nerve fiber layer, and an excavated optic nerve head with advanced-stage glaucoma. Imaging was performed using anterior segment optical coherence tomography to detect the iris configuration. In the heterochromic iris portion, the normal part of the iris showed a clear hyperreflective signal of the anterior border layer, while atrophy of the pigmented anterior border layer showed a hyporeflective area of the anterior surface resulting in reduced light absorption. Two mutations of the endothelin receptor type B gene were recognized in this study. The first (c.1111G>A on exon 7) leads to an amino acid change from glycine to serine at codon 371. Sanger verification revealed that this mutation is inherited from the mother. The other mutation (c.553G>A) leads to an amino acid change from valine to methionine at codon 185. Sanger verification showed that this mutation was inherited from the father.ConclusionWaardenburg syndrome shows a remarkable diversity in clinical presentation and morphology. This disease can also present with open-angle glaucoma. Sequencing analysis revealed two heterozygous mutations in the EDNRB gene in this patient, inherited from his mother and father, respectively. These two sites constitute a compound heterozygous variation.

Automated segmentation of diabetic macular edema in OCT B‐scan images based on RCU‐Net

AbstractDiabetic macular edema (DME) is a typical fundus disease that can cause blindness in severe cases. The morphology of the inner limiting membrane (ILM) to the retinal pigment epithelium (RPE) layer in the retina and the macular edema (ME) area are important features for the diagnosis of DME. Doctors usually use non‐invasive and high‐resolution optical coherence tomography (OCT) to examine the fundus of the patient. However, manual diagnosis has low efficiency and strong subjectivity. Realizing the automatic segmentation of the ILM‐RPE layer and ME is extremely important for the early diagnosis of DME. In this paper, the attention mechanism based on residual convolution module U‐Net (RCU‐Net) is proposed for the automatic segmentation of the retinal layer and cystoid edema lesions. Through the fusion of the residual structure and CBAM for feature extraction, the useful features in the channel and space are effectively strengthened, and the network can better learn different levels of information. The proposed network is combined with the Lovász‐softmax loss, which can better target the correlation between targets to obtain the optimal segmentation model during training. Finally, this paper compares the proposed method with several other segmentation methods. The experimental results show that the of the method in this model reaches 88.595%, and the reaches 99.171%. The RCU‐Net proposed in this paper is used to segment the ILM‐RPE layer and ME region in the retina OCT B‐scan images, and its overall performance is better than other networks.

A novel mutation of CYP4V2 gene associated with Bietti crystalline dystrophy complicated by choroidal neovascularization.

To investigate the clinical characteristics and genetic features of a Bietti crystalline dystrophy (BCD) proband in a Chinese family. A Chinese female diagnosed with BCD complicated by bilateral choroidal neovascularization (CNV) and her parents underwent complete ophthalmic examinations, including fundus autofluorescence (AF), fundus photography (FP), fundus fluorescein angiography (FFA), visual field testing, full-field electroretinography (ERG), optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA). The sequencing of the CYP4V2 gene was performed to the whole family. Bilateral tiny glittering crystal-like deposits and differing extent of atrophy of the retinal pigment epithelium (RPE) were found in the posterior pole of her fundus. The diffuse hypo-fluorescence shown on AF images and window defects shown on FFA both indicated the atrophy of the RPE and choriocapillaris. OCT showed the thinning of the RPE and choriocapillaris layer, ellipsoid zone (EZ) band defect and CNV in both eyes. OCTA images proofed bilateral type 2 CNV. The visual field test showed central and paracentral scotoma. ERG showed a slightly decreased b-wave in scotopic ERG. Gene sequencing identified three mutations of the CYP4V2 gene, c.802_807del, c.810delT, and c.1388G>A. The mutation c.1388G>A was a novel substitution mutation. The novel mutation c.1388G>A may be a possible cause that could induce the clinical phenotype of BCD.

Microglia Prevent the Loss of Visual Function in the Aging Retina by Maintaining the Health of Retinal Pigment Epithelial Cells

Even in healthy individuals, aging leads to the progressive deterioration of visual function that coincides with increasing cellular dysfunction in retinal neurons and retinal pigment epithelial (RPE) cells. Interestingly, aging also coincides with the migration of microglia from the inner to the outer retina where they reside in the subretinal space between photoreceptor outer segments and the apical surface of RPE. Healthy young microglia act as the immune sentinels of the retina, and thus are protective and maintain retinal homeostasis. However, age alters cellular functions and the role of aging subretinal microglia is not known. Here we investigated whether aged microglia residing in the subretinal space are either preventing or promoting loss of visual function.Microglia were depleted in 33‐month‐old C57/BL6 mice fed for 6 weeks with a chow containing PLX5622, a small molecule inhibitor of colony‐stimulating factor‐1 receptor (Csf1r) which is expressed by microglia and is required for their proliferation, differentiation, and survival. As a negative control, age‐matched mice received a control diet. Following microglia depletion, the optomotor reflex (OMR) was used to assess visual acuity and contrast sensitivity and electroretinogram (ERG) assessed retinal function. Morphological analysis was determined by immunohistochemical staining and TEM.To distinguish microglia from infiltrating macrophages, retinas from old mice were stained with P2RY12, a microglia‐specific marker. The vast majority of cells residing between the photoreceptor outer segments and RPE layer in old mice were P2RY12+ microglia. These cells displayed a highly amoeboid and activated morphology and were filled with autofluorescence droplets similar to lipofuscin. PLX5622 treatment depleted up to 90% of the microglia. Microglia preserved visual function, and in the absence of microglia, there was a significant loss of contrast sensitivity and ERG c‐wave, as compared with untreated controls. Loss of microglia coincided with a loss of RPE cells and increased RPE swelling indicating that microglia support RPE in aged animals. TEM indicates that subretinal microglia actively phagocytize shed photoreceptor outer segments, thereby compensating for the known age‐related decline of RPE phagocytosis.We conclude that microglia in aging mice migrate to the subretinal space of the outer retina to support and maintain RPE cell functions that preserves vision.

Efficacy of Navigated Laser Photocoagulation for Chronic Central Serous Chorioretinopathy: A Retrospective Observational Study.

Background. No consensus has been reached regarding the management of central serous chorioretinopathy (CSCR). We aimed to investigate the efficacy of navigated laser treatment for chronic CSCR and changes in the morphology of the retinal pigment epithelium (RPE). In this retrospective observational study, 19 patients with subjective symptoms admitted to the Nanjing Medical University Affiliated Eye Hospital were included between January 2021 and August 2021. All patients underwent visual acuity and optical coherence tomography (OCT) examination during follow-up. Fluorescein angiography (FA) was performed at baseline and at the final follow-up to confirm the dye leakage sites. The mean logMAR BCVA at baseline and at the end of follow-up was 0.49 ± 0.24 and 0.24 ± 0.15, respectively. The mean logMAR BCVA 3 months after treatment was significantly better than that before treatment (p = 0.002). Significant improvements were observed in central macular thickness (CMT) and subfoveal choroidal thickness (SFCT) after navigated laser photocoagulation (p < 0.0001). Subretinal fluid was completely resolved in 13 (68%) of 19 eyes at 3 months. RPE lesions on OCT images showed RPE detachment in 17 eyes (61.5%), small protrusion of the RPE layer in 5 eyes (7.5%), and a rough RPE layer in 4 eyes (31%). After laser treatment, 9 points (35%) showed retinal detachment, and 10 (38.5%) regions showed an irregular RPE layer. An irregularly protruded RPE layer was also observed in different regions of the leakage spot in 5 (19%) eyes, and RPE defects were seen in 2 (7.5%) eyes. Navigated laser photocoagulation for chronic CSCR can achieve substantial anatomical and visual improvement. OCT outcomes may provide new information to facilitate understanding of the mechanism of chronic CSCR. Navigated laser photocoagulation should be chosen as an optimal treatment option in patients with chronic CSCR who cannot afford photodynamic therapy.

First observation of intraocular extranodal natural killer/T-cell lymphoma secondary to a retroperitoneal tumour: a case report and comparative review

BackgroundVitreoretinal lymphomas are difficult to diagnose due to their insidious onset and inaccessible focal points. Natural killer/T-cell derived malignancies are rare as intraocular lymphomas and usually have a rapid progression and a poor prognosis. Therefore, it is essential to make a definite diagnosis, especially differentially with B-cell-derived lymphomas, which account for most cases of vitreoretinal lymphomas.Case presentationThis case report describes a 55-year-old female reporting a 10-month history of painless decline in her vision of the right eye. Optical coherence tomography of the patient revealed hyperreflective nodules and irregular humps in the retinal pigment epithelium layer. The right vitreous was aspirated for diagnostic assessment, revealing an interleukin-10 level of 39.4 pg/mL and an interleukin-10/interleukin-6 ratio of 1.05. The right vitreous humor was positive for Epstein–Barr virus DNA. Upon a systemic examination, a high metabolic nodule was found in the retroperitoneal area and proven to be positive for Epstein–Barr virus-encoded mRNA, CD2, CD3ε, TIA-1, and Ki-67. Considering the homology of the two lesions, the patient was diagnosed with metastatic vitreoretinal lymphoma secondary to retroperitoneal extranodal natural killer/T-cell derived lymphoma. The patient received systemic chemotherapy and regular intravitreal injections of methotrexate. Her visual acuity of the right eye had improved from 20/125 to 20/32 at the latest follow-up. No new lesions were found.ConclusionsA definitive diagnosis of vitreoretinal lymphoma is challenging. On some occasions in which pathological evidence is missing, the available examination results and clinical observations must be comprehensively considered. This study herein summarized pertinent pieces of literature and reports and reviewed available practicable methods to make a definitive diagnosis of intraocular extranodal natural killer/T-cell lymphoma, which was particularly distinct from the common diffuse large B-cell lymphomas.

Evaluation of Retinal Layer Thicknesses in Patients with Keratoconus Using Retinal Layer Segmentation Analysis.

To conduct an evaluation of the effects of irregular astigmatism on the retinal nerve fiber layer (RNFL) and the retinal layers observed using spectral-domain optical coherence tomography (SD-OCT) in patients who had keratoconus (KC). A total of 255 eyes from 255 individuals, comprising 72 eyes of KC patients, 70 eyes of patients with astigmia, and 113 eyes of healthy controls were included in the analysis. RNFL scan maps (comprising global, temporal, superotemporal, inferotemporal, nasal, inferonasal, and superonasal maps) and macular thickness (MT) maps of a standard from the Early Treatment Diabetic Retinopathy Study (ETDRS) grid were assessed. The measurements were segmented automatically using Spectralis software, and included the RNFL, inner and outer plexiform layers (IPL, OPL), inner and outer nuclear layers (INL, ONL), ganglion cell layer, retinal pigment epithelium (RPE) in the central 6-mm ETDRS subfield. The RNFL thickness in the KC group was lower when compared with the other two groups; however, statistically significant differences were noted in the global, temporal, superotemporal, and inferotemporal sectors (p < 0.05 for all). All of the central MT parameters showed significant variation among the groups, while a statistically significant decrease was noted in the KC group, except in the inferior outer sector (p = 0.741). In the segmentation analysis, the KC group had the significantly lowest IPL, ONL, RPE, and outer retinal layer (ORL) thickness among the groups (p < 0.05 for each). The astigmatic group was similar to the control group with regard to these parameters (p > 0.05 for each). The eyes in the KC group appeared to have a thinner RNFL and MT when compared to those in the astigmatic and control groups. The ORLs, especially the ONL and RPE, were the most affected component of the macula in the KC group.

MTOR activity is essential for retinal pigment epithelium regeneration in zebrafish.

The retinal pigment epithelium (RPE) plays numerous critical roles in maintaining vision and this is underscored by the prevalence of degenerative blinding diseases like age-related macular degeneration (AMD), in which visual impairment is caused by progressive loss of RPE cells. In contrast to mammals, zebrafish possess the ability to intrinsically regenerate a functional RPE layer after severe injury. The molecular underpinnings of this regenerative process remain largely unknown yet hold tremendous potential for developing treatment strategies to stimulate endogenous regeneration in the human eye. In this study, we demonstrate that the mTOR pathway is activated in RPE cells post-genetic ablation. Pharmacological and genetic inhibition of mTOR activity impaired RPE regeneration, while mTOR activation enhanced RPE recovery post-injury, demonstrating that mTOR activity is essential for RPE regeneration in zebrafish. RNA-seq of RPE isolated from mTOR-inhibited larvae identified a number of genes and pathways dependent on mTOR activity at early and late stages of regeneration; amongst these were components of the immune system, which is emerging as a key regulator of regenerative responses across various tissue and model systems. Our results identify crosstalk between macrophages/microglia and the RPE, wherein mTOR activity is required for recruitment of macrophages/microglia to the RPE injury site. Macrophages/microglia then reinforce mTOR activity in regenerating RPE cells. Interestingly, the function of macrophages/microglia in maintaining mTOR activity in the RPE appeared to be inflammation-independent. Taken together, these data identify mTOR activity as a key regulator of RPE regeneration and link the mTOR pathway to immune responses in facilitating RPE regeneration.

Clinical classification, visual outcomes, and optical coherence tomographic features of 48 patients with posterior sympathetic ophthalmia

BackgroundTo investigate the clinical manifestations, visual outcomes and optical coherence tomographic (OCT) features of patients with posterior sympathetic ophthalmia (PSO).MethodsWe performed a retrospective review of 48 patients diagnosed with PSO between January 2013 and December 2019. We compared the clinical and OCT features among different clinical types of PSO.ResultsPSO could be classified into two types according to whether the fundus exhibited serous retinal detachment (SRD) or multifocal choroiditis (MFC). There were 41 patients (85.4%) with SRD and 7 patients (14.6%) with MFC. The latent period of patients with MFC was significantly longer than that of patients with SRD (P = 0.002). The final visual acuity of patients with MFC was significantly worse than that of patients with SRD (P = 0.0001). In patients with acute SRD, OCT revealed that the mean height of retinal detachment in the fovea was 528.8 ± 437.5 μm. After treatment, the retina reattached in all patients and the band structures of the outer retina were restored in most patients (92.7%). In patients with acute MFC, the OCT images revealed inflammatory lesions on the retinal pigment epithelium layer. After treatment, the OCT images showed hyperreflective fibrosis of the lesions and loss of the outer retinal band structures in all patients.ConclusionsWe found that PSO could be classified according to the presence of SRD or MFC. The visual prognosis differed significantly between these types of PSO. OCT imaging is useful for clinical classification and monitoring of retinal changes after treatment.

Dark Adaptation and Its Role in Age-Related Macular Degeneration.

Dark adaptation (DA) refers to the slow recovery of visual sensitivity in darkness following exposure to intense or prolonged illumination, which bleaches a significant amount of the rhodopsin. This natural process also offers an opportunity to understand cellular function in the outer retina and evaluate for presence of disease. How our eyes adapt to darkness can be a key indicator of retinal health, which can be altered in the presence of certain diseases, such as age-related macular degeneration (AMD). A specific focus on clinical aspects of DA measurement and its significance to furthering our understanding of AMD has revealed essential findings underlying the pathobiology of the disease. The process of dark adaptation involves phototransduction taking place mainly between the photoreceptor outer segments and the retinal pigment epithelial (RPE) layer. DA occurs over a large range of luminance and is modulated by both cone and rod photoreceptors. In the photopic ranges, rods are saturated and cone cells adapt to the high luminance levels. However, under scotopic ranges, cones are unable to respond to the dim luminance and rods modulate the responses to lower levels of light as they can respond to even a single photon. Since the cone visual cycle is also based on the Muller cells, measuring the impairment in rod-based dark adaptation is thought to be particularly relevant to diseases such as AMD, which involves both photoreceptors and RPE. Dark adaptation parameters are metrics derived from curve-fitting dark adaptation sensitivities over time and can represent specific cellular function. Parameters such as the cone-rod break (CRB) and rod intercept time (RIT) are particularly sensitive to changes in the outer retina. There is some structural and functional continuum between normal aging and the AMD pathology. Many studies have shown an increase of the rod intercept time (RIT), i.e., delays in rod-mediated DA in AMD patients with increasing disease severity determined by increased drusen grade, pigment changes and the presence of subretinal drusenoid deposits (SDD) and association with certain morphological features in the peripheral retina. Specifications of spatial testing location, repeatability of the testing, ease and availability of the testing device in clinical settings, and test duration in elderly population are also important. We provide a detailed overview in light of all these factors.

Zic5 stabilizes Gli3 via a non-transcriptional mechanism during retinal development.

The Zic family of zinc finger transcription factors plays a critical role in multiple developmental processes. Using loss-of-function studies, we find that Zic5 is important for the differentiation of retinal pigmented epithelium (RPE) and the rod photoreceptor layer through suppressing Hedgehog (Hh) signaling. Further, Zic5 interacts with the critical Hh signaling molecule, Gli3, through the zinc finger domains of both proteins. This Zic5-Gli3 interaction disrupts Gli3/Gli3 homodimerization, resulting in Gli3 protein stabilization via a reduction in Gli3 ubiquitination. During embryonic Hh signaling, the activator form of Gli is normally converted to a repressor form through proteosome-mediated processing of Gli3, and the ratio of Gli3 repressor to full-length (activator) form of Gli3 determines the Gli3 repressor output required for normal eye development. Our results suggest Zic5 is a critical player in regulating Gli3 stability for the proper differentiation of RPE and rod photoreceptor layer during Xenopus eye development.

Inhibition of DUSP6 Activates Autophagy and Rescues the Retinal Pigment Epithelium in Sodium Iodate-Induced Retinal Degeneration Models In Vivo and In Vitro.

Autophagy plays a protective role in the retinal pigment epithelium (RPE) by eliminating damaged organelles in response to reactive oxygen species (ROS). Dual-specificity protein phosphatase 6 (DUSP6), which belongs to the DUSP subfamily, works as a negative-feedback regulator of the extracellular signal-regulated kinase (ERK) pathway. However, the complex interplay between DUSP6 and autophagy induced by ROS in RPE is yet to be investigated. To investigate the relationship between DUSP6 and autophagy, we exposed the ARPE-19 cell line and C57BL/6N mice to sodium iodate (NaIO3) as an oxidative stress inducer. Our data showed that the inhibition of DUSP6 activity promotes autophagy flux through the ERK pathway via the upregulation of immunoblotting expression in ARPE-19 cells. Live imaging showed a significant increase in autophagic flux activities, which suggested the restoration autophagy after treatment with the DUSP6 inhibitor. Furthermore, the mouse RPE layer exhibited an irregular structure and abnormal deposits following NaIO3 injection. The retina layer was recovered after being treated with DUSP6 inhibitor; this suggests that DUSP6 inhibitor can rescue retinal damage by restoring the mouse retina’s autophagy flux. This study suggests that the upregulation of DUSP6 can cause autophagy flux malfunctions in the RPE. The DUSP6 inhibitor can restore autophagy induction, which may serve as a potential therapeutic approach for retinal degeneration disease.

A Device-Independent, Shape Preserving Retinal Optical Coherence Tomography Image Alignment Method Applying TV-Unet for RPE Layer Detection

Retinal optical coherence tomography (OCT) images are widely used in diagnosis of ocular conditions. However, random shift and orientation changes of the retinal layers in OCT B-scans yield to appearance variations across the scans. These variations reduce the accuracy of the algorithms applied in the analysis of OCT images. In this study, we propose a preprocessing step to compensate these variations and align B-scans. At first, by incorporating total variation (TV) loss in the well-known Unet model, we propose a TV-Unet model to accurately detect the retinal pigment epithelium (RPE) layer in each B-scan. Then we use the detected RPE layer in the alignment method to form a curvature curve and a reference line. A novel window transferring-based alignment approach is applied to force the curve points to form a straight line, while preserving the shape and size of the pathological lesions. Since detection of RPE layer is a crucial step in the proposed alignment method, we utilized various datasets to train and test the TV-Unet and provided a multimodal, device-independent OCT image alignment method. The TV-Unet localizes the RPE layer in OCT images with low boundary error (maximum of 1.94pixels) and high Dice coefficient (minimum of 0.98). Quantitative and qualitative results indicated that the proposed method can efficiently detects the RPE layer and align OCT images while preserving the structure and size of the retinal lesions (biomarkers) in the OCT scans.

Opportunities for agent based modeling of retinal stem cell transplantation.

Opportunities for agent based modeling of retinal stem cell transplantation.

Mechanism of Hypoxia Inducible Factor-1α (HIF-1α) in Choroidal Neovascularization in Macular Lutea of High Myopia

To explore the changes in the expression of hypoxia inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) in the process of choroidal neovascularization (CNV) in the macular area of cases with form deprivation myopia (FDM), in this study, 36 healthy mice were selected as research subjects for analysis. Specifically, they were randomly divided into test group (n = 18) and control group (n = 18). The right eye of the test group mice underwent form deprivation for 6 weeks to induce FDM, also known as FDM group. Five mice were randomly selected from FDM group and control group at 6 time points (before photocoagulation, at 7 d, 14 d, 21 d, 28 d, and 35 d after photocoagulation), respectively, for fluorescein angiography and hematoxylin-eosin staining (HE) staining to observe differences in the retina. It was found that the retina of Control group mice was well-structured with clear stratification, while that of the test group mice was severely damaged with a disordered structure, manifested as edema and swelling and damaged Bruch membrane and retinal pigment epithelium (RPE) layer. Furthermore, macrophages and RPE cells were observed in the photocoagulation area, and there was a high-fluorescence area with a blurred margin in the fundus, indicating the formation of new blood vessels. The immunohistochemical experiment revealed that within three weeks after the surgery, HIF-1α was highly expressed in the test group, and the expression level was obviously higher than the Control group. The real-time quantitative polymerase chain reaction (PCR) results showed that the expression level of VEGF and HIF-α in the test group was obviously higher than the Control group within three weeks after the surgery. The Western blot experiment was performed 1 week after the surgery, and it was noted that the expression level of VEGF and HIF-1α were higher in the test group versus the Control group. In summary, HIF-1α is instrumental in ocular CNV, which is also associated with VEGF.

Downregulation of AlphaB-crystallin in Retinal Pigment Epithelial Cells Exposed to Diabetes-related Stimuli In Vivo and In Vitro.

AlphaB-crystallin plays a pivotal role in many diseases. However, the involvement of alphaB-crystallin in retinal pigment epithelial (RPE) cells with diabetes stimuli remains unknown. The aim of this study is to examine the alterations of RPE cells and alphaB-crystallin expression in diabetic models in vivo and in vitro. Diabetic conditions in mice were induced by streptozotocin (STZ). The thickness of the RPE/choroid complex was measured by optical coherence tomography (OCT). Periodic acid-Schiff (PAS) staining was used to investigate the choriocapillaris in histological sections of murine eyeballs and oxidative stress was evaluated using immunofluorescence with anti-4-hydroxynonenal (HNE) antibody. AlphaB-crystallin expression was examined in the RPE/choroid complex using ELISA. Real-Time PCR was performed to evaluate the alphaB-crystallin expression in cultured human RPE cells with high glucose or following advanced glycation end-products (AGE) stimulation. In diabetic mice, OCT-based RPE/choroidal layers were thickened 2 months after STZ stimulation, where PAS-positive dilated choriocapillaris was noted. Immunoreactivity of 4-HNE was strongly observed in the RPE layer, from which a significant number of RPE cells was lost. Meanwhile, alphaB-crystallin expression in 2-month STZ mice was significantly lower compared to controls. In accordance with these results, in vitro data showed that the alphaB-crystallin expression was also significantly lower in RPE cells with high glucose or following AGE stimulation compared to untreated cells. In both types of diabetic models the expression of alphaB-crystallin was found to be downregulated in RPE cells and was associated with increased levels of oxidative stress.

Adaptive optics two-photon excited fluorescence lifetime imaging ophthalmoscopy of photoreceptors and retinal pigment epithelium in the living non-human primate eye.

Fluorescence lifetime imaging has demonstrated promise as a quantitative measure of cell health. Adaptive optics two-photon excited fluorescence (TPEF) ophthalmoscopy enables excitation of intrinsic retinal fluorophores involved in cellular metabolism and the visual cycle, providing in vivo visualization of retinal structure and function at the cellular scale. Combining these technologies revealed that macaque cones had a significantly longer mean TPEF lifetime than rods at 730 nm excitation. At 900 nm excitation, macaque photoreceptors had a significantly longer mean TPEF lifetime than the retinal pigment epithelium layer. AOFLIO can measure the fluorescence lifetime of intrinsic retinal fluorophores on a cellular scale, revealing differences in lifetime between retinal cell classes.