Deep Learning-Based SD-OCT Layer Segmentation Quantifies Outer Retina Changes in Patients With Biallelic RPE65 Mutations Undergoing Gene Therapy.

Purpose: To quantify outer retina structural changes and define novel biomarkers of inherited retinal degeneration associated with biallelic mutations in RPE65 (RPE65-IRD) in patients before and after subretinal gene augmentation therapy with voretigene neparvovec (Luxturna). Methods: Application of advanced deep learning for automated retinal layer segmentation, specifically tailored for RPE65-IRD. Quantification of five novel biomarkers for the ellipsoid zone (EZ): thickness, granularity, reflectivity, and intensity. Estimation of the EZarea in single and volume scans was performed with optimized segmentation boundaries. The control group was age similar and without significant refractive error. Spherical equivalent refraction and ocular length were evaluated in all patients. Results: We observed significant differences in the structural analysis of EZ biomarkers in 22 patients with RPE65-IRD compared with 94 healthy controls. Relative EZ intensities were already reduced in pediatric eyes. Reductions of EZ local granularity and EZ thickness were only significant in adult eyes. Distances of the outer plexiform layer, external limiting membrane, and Bruch's membrane to EZ were reduced at all ages. EZ diameter and area were better preserved in pediatric eyes undergoing therapy with voretigene neparvovec and in patients with a milder phenotype. Conclusions: Automated quantitative analysis of biomarkers within EZ visualizes distinct structural differences in the outer retina of patients including treatment-related effects. The automated approach using deep learning strategies allows big data analysis for distinct forms of inherited retinal degeneration. Limitations include a small dataset and potential effects on OCT scans from myopia at least -5 diopters, the latter considered nonsignificant for outer retinal layers.

Early subclinical macular disease in asymptomatic patients with primary antiphospholipid syndrome: A quantitative multimodal retinal evaluation.

PURPOSE: To perform a quantitative multimodal evaluation in 25 patients with primary antiphospholipid syndrome (PAPS) without ocular complaints and to compare them with 25 healthy individuals. METHODS: A structural and functional ophthalmological evaluation using optical coherence tomography angiography (OCTA) and microperimetry (MP) exam in 25 patients with PAPS, followed at a tertiary rheumatology outpatient clinic, was performed. All ophthalmologic manifestations were documented and subsequent statistical analysis was performed for comparative purposes, with significance set at p < 0.05. RESULTS: We included 100 eyes of 50 subjects (25 patients with PAPS without ocular complaints and 25 healthy individuals). Quantitative OCTA assessment revealed significant differences between PAPS patients and controls in both the superficial vascular complex (SVC) and deep vascular complex (DVC) using high-speed protocol, as well as in the SVC in the high-resolution protocol. Analysis of the foveal avascular zone (FAZ) parameters showed a larger area of FAZ in the DVC in PAPS patients using the high-speed method compared to the control group (p = 0.047). In MP quantitative analysis, the PAPS group exhibited lower central (p = 0.041) and global (p < 0.001) retinal sensitivity compared to the control group, along with sectoral differences, except in the inferior sector. CONCLUSIONS: PAPS patients present lower vascular density and retinal sensitivity compared to the control group, even in patients without paracentral acute middle maculopathy (PAMM). Our findings underscore the significance of ocular evaluation beyond symptomatic assessment in these patients.

Optimizing Retinal Imaging: Evaluation of ultrasmall TiO2 nanoparticle- fluorescein conjugates for improved Fundus Fluorescein Angiography.

Fundus Fluorescein Angiography (FFA) has been extensively used for the identification, management, and diagnosis of various retinal and choroidal diseases, such as age-related macular degeneration, diabetic retinopathy, retinopathy of prematurity, among others. This exam enables clinicians to evaluate retinal morphology and the pathophysiology of retinal vasculature. However, adverse events, including from mild to severe reactions to sodium fluorescein, have been reported. Titanium dioxide nanoparticles (NPTiO2) have shown significant potential in numerous biological applications. Coating or conjugating these nanoparticles with small molecules can enhance their stability, photochemical properties, and biocompatibility, as well as increase the hydrophilicity of the nanoparticles, making them more suitable for biomedical applications. This work demonstrates the potential use of ultrasmall titanium dioxide nanoparticles conjugated with sodium fluorescein to improve the quality of angiography exams. The strategy of conjugating fluorescein with NPTiO2 successfully enhanced the fluorescence photostability of the contrast agent and increased its retention time in the retina. Preliminary in vivo and in vitro safety tests suggest that these nanoparticles are safe for the intended application demonstrating low tendency to hemolysis, and no significant changes in the retina thickness or in the electroretinography a-wave and b-wave amplitudes. Overall, the conjugation of fluorescein to NPTiO2 has produced a nanomaterial with favorable properties for use as an innovative contrast agent in FFA examinations. By providing a clear description of our methodology of analysis, we also aim to offer better perspectives and reproducible conditions for future research.

Benign Lobular Inner Nuclear Layer Proliferations of the retina.

PURPOSE: Report the clinical and imaging findings of a patient with an intraretinal benign tumor that was documented as an unexpected clinical finding after an ischemic stroke in the context of mitral valve disease. This tumor must be distinguished from retinoblastoma and other malignant neoplasms. METHODS: A patient with intraretinal tumor of the inner nuclear layer (INL) underwent a combination of ophthalmic examination, fundus photography, fluorescein angiography, optical coherence tomography (OCT), and optical coherence tomography angiography (OCT-A). RESULTS: A 64-year-old male patient with unilateral benign tumor lesions dependent on the internal retina, centered in the posterior pole, and multifocal. OCT showed that these lesions were centered within the INL at the edge of the inner plexiform layer and were not associated with other findings in the posterior pole. CONCLUSIONS: Benign Lobular Inner Nuclear Layer Proliferations (BLIP) of the Retina are recently described lesions that should be considered, given their distinctive characteristics that set them apart from other benign and malignant retinal lesions.

Multimodal imaging and genetic screening in Mexican patients with Gyrate atrophy: identification of novel OAT pathogenic variants.

PURPOSE: Description of retinal phenotype by structural and functional testing, ornithine plasma levels and mutational data of OAT gene in patients with Gyrate Atrophy (GA). METHODS: Ophthalmologic examination, fundus photography (CFP), autofluorescence (FAF), spectral-domain optical coherence tomography (SD-OCT), Goldmann perimetry (GP), full-field electroretinogram (ffERG) and chromatic perimetry (CP) testing were performed. Ornithine plasma levels were measured. Sanger sequencing mutational analysis of the coding exons and exon-intron junctions of the OAT gene were analyzed. RESULTS: Twelve eyes of seven Mexican patients with GA were included. CFF showed peripheric patches of chorioretinal atrophy; FAF revealed peripheric oval areas of hypoautofluorescence; SD-OCT exhibited outer retinal tubulations in 58%, cystoid macular edema in 50%, epiretinal membrane in 42%, foveoschisis and staphyloma in 17%, and hyperreflective deposits in 100% of the eyes; GP showed constricted visual fields in 100% of the eyes; ffERG revealed preserved photopic response in 17% and preserved scotopic response in 17% of the eyes; CP exposed a deficit in generalized response of rods and cones in 100% of the eyes. Mean ornithine plasma levels were 509.5 µmol/L. One patient with genetic confirmation of GA had normal ornithine plasma levels (48 µmol/L). Molecular findings in OAT gene detected two novel pathogenic variants: c.796 C > T (p.Gln266*) and c.721_722dupCC (p.Asp242ArgfsTer6). CONCLUSION: This study provides new information regarding functional and structural diagnosis in patients with GA, expands the understanding of retinal phenotype in patients with GA, reports two novel mutations and presents the first case of GA confirmed by genetic testing with normal ornithine levels.

Interpretable multimodal classification for age-related macular degeneration diagnosis.

Explainable Artificial Intelligence (XAI) is an emerging machine learning field that has been successful in medical image analysis. Interpretable approaches are able to "unbox" the black-box decisions made by AI systems, aiding medical doctors to justify their diagnostics better. In this paper, we analyze the performance of three different XAI strategies for medical image analysis in ophthalmology. We consider a multimodal deep learning model that combines optical coherence tomography (OCT) and infrared reflectance (IR) imaging for the diagnosis of age-related macular degeneration (AMD). The classification model is able to achieve an accuracy of 0.94, performing better than other unimodal alternatives. We analyze the XAI methods in terms of their ability to identify retinal damage and ease of interpretation, concluding that grad-CAM and guided grad-CAM can be combined to have both a coarse visual justification and a fine-grained analysis of the retinal layers. We provide important insights and recommendations for practitioners on how to design automated and explainable screening tests based on the combination of two image sources.

Prolonged Photobiomodulation with Deep Red Light Mitigates Incipient Retinal Deterioration in a Mouse Model of Type 2 Diabetes.

Diabetic retinopathy is a prevalent complication of type 2 diabetes mellitus, characterized by progressive damage to the retinal structure and function. Photobiomodulation therapy, using red or near-infrared light, has been proposed as a non-invasive intervention to mitigate retinal damage, but has been tested generally with short-term stimuli. This study aimed to evaluate the effects of prolonged photobiomodulation with deep red light on retinal structure and function in a type 2 diabetes mouse model. Transgenic LepRdb/J (db/db) mice were exposed to photobiomodulation therapy via LED devices emitting 654 nm light for 12 h daily over ten weeks and compared to untreated mice. Retinal function was evaluated by flash electroretinography, while structural changes were assessed through histology and immunohistochemistry to detect astro- and microgliosis. At 33 weeks of age, db/db mice were obese and severely diabetic, but exhibited only incipient indicators of retinal deterioration. Electroretinogram b-wave peak latencies were prolonged at intermediate flash intensities, while the outer plexiform layer displayed significantly elevated IBA1 expression. Photobiomodulation therapy prevented these two markers of early retinal deterioration but had no effect on other morphological and functional parameters. Photobiomodulation is well-tolerated and maintains potential as a complementary treatment option for diabetic retinopathy but requires further optimization of therapeutic settings and combinatory treatment approaches.

Ontogeny of Thyroid Hormone Signaling in the Retina of Zebrafish: Effects of Thyroidal Status on Retinal Morphology, Cell Survival, and Color Preference.

The retina is crucial for converting light into neuronal signals for visual perception. Understanding the retina's structure, function, and development is essential for vision research. It is known that the thyroid hormone (TH) receptor type beta 2 (TRß2) is a key element in the regulation of cone differentiation in the retina, but other elements of TH signaling, such as transporters and enzyme deiodinases, have also been implicated in retinal cell development and survival. In the present study, we investigated the expression profile of genes involved in TH signaling and analyzed the impact of thyroidal status on retinal morphology, opsin expression, cell death/proliferation profile, as well as color preference behavior during the early retina development of zebrafish larvae. mRNA expression analysis on dissected whole eyes revealed that TH signaling elements gradually increase during eye development, with dio3b being the component that shows the most dramatic change. Mutations generated by CRISPR/CAS9 in the dio3b gene, but not in the thrb gene, modifies the structure of the retina. Disruption in TH level reduces the cell number of the ganglion cell layer, increases cell death, and modifies color preference, emphasizing the critical importance of precise TH regulation by its signaling elements for optimal retinal development and function.

Quantification of Photoreceptors' Changes in a Diabetic Retinopathy Model with Two-Photon Imaging Microscopy.

Emerging evidence suggests that retinal neurodegeneration is an early event in the pathogenesis of diabetic retinopathy (DR), preceding the development of microvascular abnormalities. Here, we assessed the impact of neuroinflammation on the retina of diabetic-induced rats. For this aim we have used a two-photon microscope to image the photoreceptors (PRs) at different eccentricities in unstained retinas obtained from both control (N = 4) and pathological rats (N = 4). This technique provides high-resolution images where individual PRs can be identified. Within each image, every PR was located, and its transversal area was measured and used as an objective parameter of neuroinflammation. In control samples, the size of the PRs hardly changed with retinal eccentricity. On the opposite end, diabetic retinas presented larger PR transversal sections. The ratio of PRs suffering from neuroinflammation was not uniform across the retina. Moreover, the maximum anatomical resolving power (in cycles/deg) was also calculated. This presents a double-slope pattern (from the central retina towards the periphery) in both types of specimens, although the values for diabetic retinas were significantly lower across all retinal locations. The results show that chronic retinal inflammation due to diabetes leads to an increase in PR transversal size. These changes are not uniform and depend on the retinal location. Two-photon microscopy is a useful tool to accurately characterize and quantify PR inflammatory processes and retinal alterations.

Expanding the Phenotypic Spectrum of Pathogenic KIAA0586 Variants: From Joubert Syndrome to Hydrolethalus Syndrome.

KIAA0586 variants have been associated with a wide range of ciliopathies, mainly Joubert syndrome (JS, OMIM #616490) and short-rib thoracic dysplasia syndrome (SRTD, OMIM #616546). However, the hypothesis that this gene is involved with hydrolethalus syndrome (HSL, OMIM #614120) and orofaciodigital syndrome IV (OMIM #258860) has already been raised. Ciliopathies' clinical features are often overlapped despite differing in phenotype severity. Besides KIAA0586, HYLS1 and KIF7 are also known for being causative of ciliopathies, indicating that all three genes may have similar or converging genomic pathways. Overall, the genotypic and phenotypic spectrum of ciliopathies becomes wider and conflicting while more and more new variants are added to this group of disorders' molecular pot. In this case report we discuss the first Brazilian individual clinically diagnosed with hydrolethalus syndrome and molecular findings that demonstrate the role of KIAA0586 as a causative gene of a group of genetic disorders. Also, recent reports on individuals with intronic and exonic variants combined leading to ciliopathies support our patient's molecular diagnosis. At the same time, we discuss variable expressivity and overlapping features in ciliopathies.

Molecular hydrogen promotes retinal vascular regeneration and attenuates neovascularization and neuroglial dysfunction in oxygen-induced retinopathy mice.

BACKGROUND: Retinopathy of Prematurity (ROP) is a proliferative retinal vascular disease occurring in the retina of premature infants and is the main cause of childhood blindness. Nowadays anti-VEGF and retinal photocoagulation are mainstream treatments for ROP, but they develop a variety of complications. Hydrogen (H2) is widely considered as a useful neuroprotective and antioxidative therapeutic method for hypoxic-ischemic disease without toxic effects. However, whether H2 provides physiological angiogenesis promotion, neovascularization suppression and glial protection in the progression of ROP is largely unknown.This study aims to investigate the effects of H2 on retinal angiogenesis, neovascularization and neuroglial dysfunction in the retinas of oxygen-induced retinopathy (OIR) mice. METHODS: In this study, mice that were seven days old and either wild-type (WT) or Nrf2-deficient (Nrf2-/-) were exposed to 75% oxygen for 5 days and then returned to normal air conditions. Different stages of hydrogen gas (H2) inhalation were administered. Vascular obliteration, neovascularization, and blood vessel leakage were analyzed and compared. To count the number of neovascularization endothelial nuclei, routine HE staining of retinal sections was conducted. Immunohistochemistry was performed using DyLight 594 labeled GSL I-isolectin B4 (IB4), as well as primary antibodies against proliferating cell nuclear antigen (PCNA), glial fibrillary acidic protein (GFAP), and Iba-1. Western blots were used to measure the expression of NF-E2-related factor 2 (Nrf2), vascular endothelial growth factor (VEGF), Notch1, Dll4, and HIF-1α. Additionally, the expression of target genes such as NQO1, HO-1, Notch1, Hey1, Hey2, and Dll4 was measured. Human umbilical vein endothelial cells (HUVECs) treated with H2 under hypoxia were used as an in vitro model. RT-PCR was used to evaluate the mRNA expression of Nrf2, Notch/Dll4, and the target genes. The expression of reactive oxygen species (ROS) was observed using immunofluorescence staining. RESULTS: Our results indicate that 3-4% H2 does not disturb retinal physiological angiogenesis, but ameliorates vaso-obliteration and neovascularization in OIR mice. Moreover, H2 prevents the decreased density and reverses the morphologic and functional changes in retinal astrocytes caused by oxygen-induced injury. In addition, H2 inhalation reduces microglial activation, especially in the area of neovascularization in OIR mice. H2 plays a protective role in vascular regeneration by promoting Nrf2 activation and suppressing the Dll4-induced Notch signaling pathway in vivo. Also, H2 promotes the proliferation of HUVECs under hypoxia by negatively regulating the Dll4/Notch pathway and reducing ROS levels through Nrf2 pathway aligning with our findings in vivo.Moreover, the retinal oxygen-sensing mechanisms (HIF-1α/VEGF) are also involved in hydrogen-mediated retinal revascularization and neovascularization suppression. CONCLUSIONS: Collectively, our results indicate that H2 could be a promising therapeutic agent for POR treatment and that its beneficial effect in human ROP might involve the activation of the Nrf2-Notch axis as well as HIF-1α/VEGF pathways.

Retinal abnormalities in a patient with cutis marmorata telangiectatica congenita.

Cutis marmorata telangiectatica congenita is a rare congenital vascular malformation characterised by cutaneous vascular abnormalities, typically diagnosed at birth or in the early postnatal period. Although typically benign, this disease is associated with other systemic abnormalities, including rare ocular alterations, such as congenital glaucoma, cataracts and retinopathy.This manuscript describes a female infant, who presented with generalised livedo reticularis, a band of alopecia and cutaneous atrophy in the temporal region above the coronal suture. The patient was diagnosed with cutis marmorata telangiectatica congenita by a paediatrician, and an ophthalmological evaluation was requested. A funduscopy examination in both eyes showed temporal and superior retina with avascular areas with new vessels, venous dilations and shunts, and no retinal detachments. Given these findings, we performed retinal photocoagulation laser treatment with excellent results.This case report highlights the importance of early ophthalmological evaluation of children with this disease to prevent secondary complications, such as vitreous haemorrhage and tractional retinal detachment.

An ethologically relevant paradigm to assess defensive response to looming visual contrast stimuli.

In the animal kingdom, threat information is perceived mainly through vision. The subcortical visual pathway plays a critical role in the rapid processing of visual information-induced fear, and triggers a response. Looming-evoked behavior in rodents, mimicking response to aerial predators, allowed identify the neural circuitry underlying instinctive defensive behaviors; however, the influence of disk/background contrast on the looming-induced behavioral response has not been examined, either in rats or mice. We studied the influence of the dark disk/gray background contrast in the type of rat and mouse defensive behavior in the looming arena, and we showed that rat and mouse response as a function of disk/background contrast adjusted to a sigmoid-like relationship. Both sex and age biased the contrast-dependent response, which was dampened in rats submitted to retinal unilateral or bilateral ischemia. Moreover, using genetically manipulated mice, we showed that the three type of photoresponsive retinal cells (i.e., cones, rods, and intrinsically photoresponsive retinal ganglion cells (ipRGCs)), participate in the contrast-dependent response, following this hierarchy: cones > > rods > > > ipRGCs. The cone and rod involvement was confirmed using a mouse model of unilateral non-exudative age-related macular degeneration, which only damages canonical photoreceptors and significantly decreased the contrast sensitivity in the looming arena.

Synchronous Diagnosis of Diabetic Retinopathy by a Handheld Retinal Camera, Artificial Intelligence, and Simultaneous Specialist Confirmation.

PURPOSE: Diabetic retinopathy (DR) is a leading cause of preventable blindness, particularly in underserved regions where access to ophthalmic care is limited. This study presents a proof of concept for utilizing a portable handheld retinal camera with an embedded artificial intelligence (AI) platform, complemented by a synchronous remote confirmation by retina specialists, for DR screening in an underserved rural area. DESIGN: Retrospective cohort study. SUBJECTS: A total of 1115 individuals with diabetes. METHODS: A retrospective analysis of a screening initiative conducted in 4 municipalities in Northeastern Brazil, targeting the diabetic population. A portable handheld retinal camera captured macula-centered and disc-centered images, which were analyzed by the AI system. Immediate push notifications were sent out to retina specialists upon the detection of significant abnormalities, enabling synchronous verification and confirmation, with on-site patient feedback within minutes. Referral criteria were established, and all referred patients underwent a complete ophthalmic work-up and subsequent treatment. MAIN OUTCOME MEASURES: Proof-of-concept implementation success. RESULTS: Out of 2052 invited individuals, 1115 participated, with a mean age of 60.93 years and diabetes duration of 7.52 years; 66.03% were women. The screening covered 2222 eyes, revealing various retinal conditions. Referable eyes for DR were 11.84%, with an additional 13% for other conditions (diagnoses included various stages of DR, media opacity, nevus, drusen, enlarged cup-to-disc ratio, pigmentary changes, and other). Artificial intelligence performance for overall detection of referable cases (both DR and other conditions) was as follows: sensitivity 84.23% (95% confidence interval (CI), 82.63-85.84), specificity 80.79% (95% CI, 79.05-82.53). When we assessed whether AI matched any clinical diagnosis, be it referable or not, sensitivity was 85.67% (95% CI, 84.12-87.22), specificity was 98.86 (95% CI, 98.39-99.33), and area under the curve was 0.92 (95% CI, 0.91-0.94). CONCLUSIONS: The integration of a portable device, AI analysis, and synchronous medical validation has the potential to play a crucial role in preventing blindness from DR, especially in socially unequal scenarios. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Thinning of the retinal nerve fiber and choroidal layers in adolescents with anorexia nervosa: A controlled study.

PURPOSE: We aimed to evaluate retinal nerve fiber and choroidal layer alterations in adolescents with anorexia nervosa using spectral-domain optical coherence tomography. METHODS: Thirty patients with anorexia nervosa and 30 healthy adolescents aged 12-18 years were included in this study. Their age, sex, body mass index, anorexia nervosa type, disease duration, and spectral-domain optical coherence tomography data were recorded. RESULTS: Central macular thickness and retinal nerve fiber layer thickness in the temporal and inferior regions were significantly lesser in patients with anorexia than in healthy controls (p<0.05). Moreover, significant choroidal thinning around the foveal and subfoveal regions in patients with anorexia was observed (p<0.05). In addition, a statistically significant relation between the increase in disease duration and the thinning of the inferior retinal nerve fiber layer was detected (p<0.05). CONCLUSION: The retinal nerve fiber layer and choroidal layer thicknesses were lesser in patients with anorexia than in healthy controls. Screening for retinal indices might prevent the development of irreversible retinal pathologies in adolescents with anorexia nervosa. In addition, thinning of the retinal nerve fiber and choroidal layers could reflect structural or functional changes in the brain of adolescents with anorexia nervosa.

Chromatic vision and structural assessment in primary congenital glaucoma.

Primary congenital glaucoma is a rare disease that occurs in early birth and can lead to low vision. Evaluating affected children is challenging and there is a lack of studies regarding color vision in pediatric glaucoma patients. This cross-sectional study included 21 eyes of 13 children with primary congenital glaucoma who were assessed using the Farnsworth D-15 test to evaluate color vision discrimination and by spectral domain optical coherence tomography to measure retinal fiber layer thickness. Age, visual acuity, cup-to-disc ratio and spherical equivalent data were also collected. Global and sectional circumpapillary and macular retinal fiber layer thicknesses were measured and compared based on color vision test performance. Four eyes (19%) failed the color vision test with diffuse dyschromatopsia patterns. Only age showed statistical significance in color vision test performance. Global and sectional circumpapillary and macular retinal fiber layer thicknesses were similar between the color test outcomes dyschromatopsia and normal. While the color vision test could play a role in assessing children with primary congenital glaucoma, further studies are needed to correlate it with damage to retinal fiber layer thickness.

Novel optical coherence tomography findings in a patient with methanol toxicity: a case report.

We report a case of acute methanol toxicity with unique optical coherence tomography findings. A 56-year-old man was referred to our ophthalmology clinic with a history of handmade vodka consumption and vision loss. On ophthalmologic examination, his vision was 20/100 in his right eye and 20/200 in his left eye. Bilateral mild optic disk hyperemia was detected on fundus examination. Because of the severity of systemic symptoms in such cases, it is very difficult to include optical coherence tomography in the ophthalmologic examination. However, we managed to perform optical coherence tomography and recorded shallow subretinal fluid and a prominent middle limiting membrane sign as acute retinal structural changes in the patient. The patient was treated with hemodialysis, intravenous ethanol, and sodium bicarbonate. On the fourth day of treatment, visual acuity improved to 20/20 in both eyes. In addition, the prominent middle limiting membrane sign and subretinal fluid disappeared. In this unusual case, retinal pigment epithelium damage and retinal ischemia may have contributed to the prominent middle limiting membrane and subretinal fluid, which are novel optical coherence tomography findings of methanol toxicity.

Platelet-Activating Factor Receptor (PAFR) Regulates Retinal Progenitor/Stem Cells Profile in Ciliary Epithelium Cells.

The retina is a central nervous tissue essential to visual perception and highly susceptible to environmental damage. Lower vertebrate retinas activate intrinsic regeneration mechanisms in response to retinal injury regulated by a specialized population of progenitor cells. The mammalian retina does not have populations of progenitor/stem cells available to activate regeneration, but contains a subpopulation of differentiated cells that can be reprogrammed into retinal stem cells, the ciliary epithelium (CE) cells. Despite the regenerative potential, stem cells derived from CE exhibit limited reprogramming capacity probably associated with the expression of intrinsic regulatory mechanisms. Platelet-activating factor (PAF) is a lipid mediator widely expressed in many cells and plays an important role in stem cell proliferation and differentiation. During mammalian development, PAF receptor signaling showed important effects on retinal progenitors' cell cycle regulation and neuronal differentiation that need to be further investigated. In this study, our findings suggested a dynamic role for PAF receptor signaling in CE cells, impacting stem cell characteristics and neurosphere formation. We showed that PAF receptors and PAF-related enzymes are downregulated in retinal progenitor/stem cells derived from PE cells. Blocking PAFR activity using antagonists increased the expression of specific progenitor markers, revealing potential implications for retinal tissue development and maintenance.

Early choroidal and retinal changes detected by swept-source oct in type 2 diabetes and their association with diabetic kidney disease: a longitudinal prospective study.

BACKGROUND: To evaluate structural changes in retina and choroid in patients with type 2 diabetes (T2D) and their association with diabetic kidney disease (DKD). METHODS: T2D patients with mild or no diabetic retinopathy (DR) were followed for 3 years using structural SS-OCT and OCT angiography (OCT-A) taken every 6 months. Parameters were compared longitudinally and according to the DKD status on baseline. RESULTS: One hundred and sixty eyes from 80 patients were followed for 3 years, 72 with no DKD (nDKD) at baseline and 88 with DKD. Trend analysis of T2D showed significant thinning in GCL + and circumpapillary retinal fiber neural layer (cRFNL), choroid, and decreased vascular density (VD) in superficial plexus and central choriocapillaris with foveal avascular zone (FAZ) enlargement. Patients with no DKD on baseline presented more significant declines in retinal center and choroidal thickness, increased FAZ and loss of nasal and temporal choriocapillaris volume. In addition, the nDKD group had worse glycemic control and renal parameters at the end of the study. CONCLUSION: Our data suggests the potential existence of early and progressive neurovascular damage in the retina and choroid of patients with Type 2 Diabetes (T2D) who have either no or mild Diabetic Retinopathy (DR). The progression of neurovascular damage appears to be correlated with parameters related to glycemic control and renal damage.

Contribution of chemical and electrical transmission to the low delta-like intrinsic retinal oscillation in mice: A role for daylight-activated neuromodulators.

Basal electroretinogram (ERG) oscillations have shown predictive value for modifiable risk factors for type 2 diabetes. However, their origin remains unknown. Here, we seek to establish the pharmacological profile of the low delta-like (δ1) wave in the mouse because it shows light sensitivity in the form of a decreased peak frequency upon photopic exposure. Applying neuropharmacological drugs by intravitreal injection, we eliminated the δ1 wave using lidocaine or by blocking all chemical and electrical synapses. The δ1 wave was insensitive to the blockade of photoreceptor input, but was accelerated when all inhibitory or ionotropic inhibitory receptors in the retina were antagonized. The sole blockade of GABAA, GABAB, GABAC, and glycine receptors also accelerated the δ1 wave. In contrast, the gap junction blockade slowed the δ1 wave. Both GABAA receptors and gap junctions contribute to the light sensitivity of the δ1 wave. We further found that the day light-activated neuromodulators dopamine and nitric oxide donors mimicked the effect of photopic exposure on the δ1 wave. All drug effects were validated through light flash-evoked ERG responses. Our data indicate that the low δ-like intrinsic wave detected by the non-photic ERG arises from an inner retinal circuit regulated by inhibitory neurotransmission and nitric oxide/dopamine-sensitive gap junction-mediated communication.