Reversible Assembly of Proteins and Phenolic Polymers for Intracellular Protein Delivery with Serum Stability

The design of intracellular delivery systems for protein drugs remains a challenge due to limited delivery efficacy and serum stability. Herein, we propose a reversible assembly strategy to assemble cargo proteins and phenolic polymers into stable nanoparticles for this purpose using a heterobifunctional adaptor (2-formylbenzeneboronic acid). The adaptor is easily decorated on cargo proteins via iminoboronate chemistry and further conjugates with catechol-bearing polymers to form nanoparticles via boronate diester linkages. The nanoparticles exhibit excellent serum stability in culture media but rapidly release the cargo proteins triggered by lysosomal acidity and GSH after endocytosis. In a proof-of-concept animal model, the strategy successfully transports superoxide dismutase to retina via intravitreal injection and efficiently ameliorates the oxidative stress and cellular damage in the retina induced by ischemia-reperfusion (I/R) with minimal adverse effects. The reversible assembly strategy represents a robust and efficient method to develop serum-stable systems for the intracellular delivery of biomacromolecules.

Trabeculectomy with concurrent intravitreal bevacizumab in neovascular glaucoma

PURPOSE

To evaluate the clinical efficacy of concurrent intravitreal bevacizumab (IVB) injection with trabeculectomy with mitomycin-C (MMC) in neovascular glaucoma (NVG).

METHODS

Patients with NVG who underwent trabeculectomy with concurrent IVB (group 1) and those who underwent IVB sequentially, followed by trabeculectomy with MMC (group 2) in 1-2 weeks between January 2021 and August 2022, were included in this retrospective hospital-based study. The need for medications for intraocular pressure (IOP) control at 6 months in the two groups was the primary outcome measured and compared between the groups. The association of the need for medications postoperatively with clinical variables was assessed using stepwise multivariate regression statistics.

RESULTS

We finally included 40 patients ( n = 12 in group 1, n = 28 in group 2) with no significant differences in presenting age between groups. The IOP at 1 day and 1 week were not significantly different between groups though the IOP at 1, 3, and 6 months. IOP was lower in group 1 eyes with the 6-month IOP, being significantly lower in group 1, P = 0.05. Three eyes in group 1 and 11 eyes in group 2 required anti-glaucoma medications in the postoperative period. Multivariate regression identified preoperative IVB >3 (β =0.7, P < 0.001) and recurrent vitreous hemorrhage (β = 0.7, P = 0.004) as prognostic factors ( R2 = 40.6%) determining the need for anti-glaucoma medication (AGM) postoperatively in both groups.

CONCLUSION

Concurrent IVB with trabeculectomy with mitomycin-C is a feasible alternative in patients with NVG with refractory high-presenting IOP. This may serve to address raised IOP as well as retinal ischemia, thereby improving surgical success rates in the most challenging NVG cases.

The Effect of S-Allyl L-Cysteine on Retinal Ischemia: The Contributions of MCP-1 and PKM2 in the Underlying Medicinal Properties

Retinal ischemia plays a vital role in vision-threatening retinal ischemic disorders, such as diabetic retinopathy, age-related macular degeneration, glaucoma, etc. The aim of this study was to investigate the effects of S-allyl L-cysteine (SAC) and its associated therapeutic mechanism. Oxidative stress was induced by administration of 500 μM H2O2 for 24 h; SAC demonstrated a dose-dependent neuroprotective effect with significant cell viability effects at 100 μM, and it concurrently downregulated angiogenesis factor PKM2 and inflammatory biomarker MCP-1. In a Wistar rat model of high intraocular pressure (HIOP)-induced retinal ischemia and reperfusion (I/R), post-administration of 100 μM SAC counteracted the ischemic-associated reduction of ERG b-wave amplitude and fluorogold-labeled RGC reduction. This study supports that SAC could protect against retinal ischemia through its anti-oxidative, anti-angiogenic, anti-inflammatory, and neuroprotective properties.

Implementation of a retinal stroke-code protocol results in visual recovery in patients receiving reperfusion therapies

INTRODUCTION

Reperfusion therapies represent promising treatments for patients with Central Retinal Artery Occlusion (CRAO), but access is limited due to low incidence and lack of protocols. We aimed to describe the benefit of implementing a Retinal Stroke-Code protocol regarding access to reperfusion, visual acuity and aetiological assessment.

PATIENTS AND METHODS

Prospective cohort study performed at a Comprehensive Stroke Centre. Criteria for activation were sudden monocular, painless vision loss within 6 h from onset. Eligible patients received IAT when immediately available and IVT otherwise. All patients were followed by ophthalmologists to assess best-corrected visual acuity (BCVA) and visual complications, and by neurologists for aetiological workup. Visual amelioration was defined as improvement of at least one Early Treatment Diabetic Retinopathy Study (ETDRS) letter from baseline to 1 week.

RESULTS

Of 49 patients with CRAO, 15 (30.6%) received reperfusion therapies (12 IVT, 3 IAT). Presentation beyond 6 h was the main contraindication. Patients receiving reperfusion therapies had better rates of visual improvement (33.3% vs 5.9%, p = 0.022). There were no complications related to reperfusion therapies. Rates of neovascular glaucoma were non-significantly lower in patients receiving reperfusion therapies (13.3% vs 20.6%, p = 0.701). Similar rates of atherosclerotic, cardioembolic and undetermined aetiologies were observed, leading to 10 new diagnosed atrial fibrillation and five carotid revascularizations.

CONCLUSION

A comprehensive acute management of CRAO is feasible despite low incidence. In our study, reperfusion therapies were safe and associated with higher rates of visual recovery. A similar etiological workup than ischemic stroke led to of high proportion of underlying aetiologies.

Case series of retinal vein occlusions showing early recovery using oral l-methylfolate

This case series describes the aggregate rate of recovery in five consecutive subjects (six eyes) with retinal vein occlusion (RVO) who received l-methylfolate and other vitamins via Ocufolin®, a medical food. Subjects were followed for 10-33 months by a single ophthalmologist. Ocufolin® was prescribed at the time of diagnosis and subjects remained on the regimen throughout the time of observation. Examinations were performed in an un-masked fashion at 3-month intervals with recording of best corrected visual acuity (BCVA), average retinal nerve fiber layer (ARNFL) and central macular thickness (CMT), and fundus (examination of the retina, macula, optic nerve, and vessels) photography. Testing was done for vitamin deficiencies, vascular and coagulable risk factors, and methylenetetrahydrofolate reductase (MTHFR) polymorphisms. Vitamin deficiencies and vascular risk factors were found in all subjects, and all four tested subjects carried at least one MTHFR polymorphism. By the end of the study period BCVA in all subjects was 20/25 or better. Cystoid macular edema was identified and measured by optical coherence tomography (OCT). The percent change was calculated and plotted at 3-month intervals using the percent change in thickness from the time of diagnosis and percent change toward normative values for ARNFL and CMT. The total reduction in thickness of ARNFL and CMT from time of diagnosis was 44.19% and 30.27%, respectively. The comparison to normative data shows a reduction of ARNFL from 164.2% to 94% and CMT from 154.4% to 112.7% of normal thickness (100%). Plots showed the aggregate recovery was most rapid over the first 3 months and slowed over the next 3 months with most of the recovery taking place within 6 months of treatment. The rate of improvement in BCVA and resolution of retinal thickening was found to be better than predicted on historical grounds. No subjects progressed from nonischemic to ischemic RVO. Vitamin deficiencies, vascular risk factors, and genetic predisposition to oxidative stress were common in this RVO series. It appears that addressing these factors with Ocufolin® had a salutary effect on recovery.

Telemedicine for Acute Monocular Visual Loss: A Retrospective Large Telestroke Network Experience

Introduction: Central retinal artery occlusion (CRAO) is an under-recognized stroke subtype that may benefit from hyperacute reperfusion therapies. We aimed to evaluate the ability of telestroke activations to provide CRAO diagnosis and thrombolysis. Methods: This retrospective observational study investigates all encounters conducted for acute visual loss between 2010 and 2021 in our multicentric Mayo Clinic Telestroke Network. Demographics, time from visual loss to telestroke evaluation, ocular examination, diagnostic, and therapeutic recommendations were collected for CRAO subjects. Results: Out of 9,511, 49 encounters (0.51%) were conducted for an acute ocular complaint. Five patients had possible CRAO, and 4 presented within 4.5 h from symptom onset (range 1.5-5 h). None received thrombolytic therapy. All telestroke physicians recommended ophthalmology consultation. Conclusion: Current telestroke assessment of acute visual loss is suboptimal and patients eligible for acute reperfusion therapies may not be offered treatment. Teleophthalmologic evaluations and advanced ophthalmic diagnostic tools should complement telestroke systems.

Analysis of Risk Factors for Revitrectomy in Eyes with Diabetic Vitreous Hemorrhage

Purpose

We aimed to investigate the risk factors associated with revitrectomy in eyes with diabetic vitreous hemorrhage and to determine the prognosis of these patients at least one year postoperatively.

Patients and Methods

This retrospective case-control study had a minimum follow-up period of one year. Patients were divided into single vitrectomy group (control group, n=202) and revitrectomy group (case group, n=36) for analysis. The indications, number, and timing of revitrectomies were documented. And the revitrectomy group was further divided into two vitrectomies group (n=30) and three or more vitrectomies group (n=6). The best-corrected visual acuity (BCVA) at the last follow-up and the occurrence of neovascular glaucoma (NVG) were compared among the single vitrectomy, two vitrectomies and three or more vitrectomies groups. We conducted a thorough collection of patient data and used univariate and binary logistic regression analyses to identify the risk factors associated with revitrectomy.

Results

A total of 197 patients (238 eyes) were included. Thirty-six eyes (15.1%) required revitrectomy with six eyes (2.5%) undergoing three or more vitrectomies during the follow-up period. The median duration of the second vitrectomy was 3 (2-6) months. The indications for a second vitrectomy included 28 eyes (77.8%) of postoperative vitreous hemorrhage and 7 eyes (22.2%) combined with tractional retinal detachment. Patients undergoing three or more vitrectomies had significantly worse postoperative BCVA and a higher incidence of NVG (P<0.01). Fibrinogen> 4 g/L (P<0.001) and preoperative anti-vascular endothelial growth factor intravitreal injection (P=0.015) were independent risk factors for revitrectomy, and glycated hemoglobin A1c (HbA1c)>10% (P=0.049) showed significant difference only in univariate analysis.

Conclusion

Patients requiring revitrectomy tended to have higher fibrinogen levels, tightly adhered fibrovascular membranes, higher HbA1c levels, and worse prognoses.

Double Trouble: Eales Disease in a Background of Paradoxical Embolism

Eales disease is an idiopathic retinal vasculitis that mainly affects the periphery of the retina. The disease commonly manifests as peripheral retinal perivasculitis, peripheral retinal capillary nonperfusion, neovascularization, and recurrent vitreous hemorrhage. Here, we present the case of a 36-year-old male who was diagnosed with Eales disease after presenting with sudden onset flashes of light, reduced visual acuity, and a black spot in his left eye. Upon examination, his left eye exhibited a superior non-foveal branch retinal artery occlusion (BRAO) with a sludged blood column, an old extramacular branch retinal vein occlusion (BRVO) with hemorrhage, and vascular sheathing. Initial laboratory investigations, including antibody testing for causes of retinal ischemia and stroke workup, were negative. Later, the patient presented with a BRAO in the right eye and a cerebral infarction shortly thereafter, further complicating his clinical picture. A diagnosis of Eales disease was made based on the evolution of retinal findings showing peripheral non-perfusion, vascular sheathing, collateral formation, neovascularization with leakage, absence of additional BRAOs following repair of his patent foramen ovale, and lack of other explanatory conditions. The initiation of systemic corticosteroids resulted in the improvement and stabilization of his vision. This case highlights the challenges in diagnosing Eales disease, underscoring the importance of timely identification for the appropriate management and prevention of vision loss.

Mural Serum Response Factor (SRF) Deficiency Provides Insights into Retinal Vascular Functionality and Development

Serum response factor (SRF) controls the expression of muscle contraction and motility genes in mural cells (MCs) of the vasculature. In the retina, MC-SRF is important for correct angiogenesis during development and the continuing maintenance of the vascular tone. The purpose of this study was to provide further insights into the effects of MC SRF deficiency on the vasculature and function of the mature retina in SrfiMCKO mice that carry a MC-specific deletion of Srf. Retinal morphology and vascular integrity were analyzed in vivo via scanning laser ophthalmoscopy (SLO), angiography, and optical coherence tomography (OCT). Retinal function was evaluated with full-field electroretinography (ERG). We found that retinal blood vessels of these mutants exhibited different degrees of morphological and functional alterations. With increasing severity, we found vascular bulging, the formation of arteriovenous (AV) anastomoses, and ultimately, a retinal detachment (RD). The associated irregular retinal blood pressure and flow distribution eventually induced hypoxia, indicated by a negative ERG waveform shape. Further, the high frequency of interocular differences in the phenotype of individual SrfiMCKO mice points to a secondary nature of these developments far downstream of the genetic defect and rather dependent on the local retinal context.

Intraocular Adeno-Associated Virus-Mediated Transgene Endothelin-1 Delivery to the Rat Eye Induces Functional Changes Indicative of Retinal Ischemia-A Potential Chronic Glaucoma Model

Endothelin-1 (ET-1) overactivity has been implicated as a factor contributing to glaucomatous neuropathy, and it has been utilized in animal models of retinal ischemia. The functional effects of long-term ET-1 exposure and possible compensatory mechanisms have, however, not been investigated. This was therefore the purpose of our study. ET-1 was delivered into rat eyes via a single intravitreal injection of 500 µM or via transgene delivery using an adeno-associated viral (AAV) vector. Retinal function was assessed using electroretinography (ERG) and the retinal expression of potentially compensatory genes was evaluated by means of qRT-PCR. Acute ET-1 delivery led to vasoconstriction and a significant reduction in the ERG response. AAV-ET-1 resulted in substantial transgene expression and ERG results similar to the acute ET-1 injections and comparable to other models of retinal ischemia. Compensatory changes were observed, including an increase in calcitonin gene-related peptide (CGRP) gene expression, which may both counterbalance the vasoconstrictive effects of ET-1 and provide neuroprotection. This chronic ET-1 ischemia model might be especially relevant to glaucoma research, mimicking the mild and repeated ischemic events in patients with long-term vascular dysfunction. The compensatory mechanisms, and particularly the role of vasodilatory CGRP in mitigating the retinal damage, warrant further investigation with the aim of evaluating new therapeutic strategies.

Stable Gastric Pentadecapeptide BPC 157-Possible Novel Therapy of Glaucoma and Other Ocular Conditions

Recently, stable gastric pentadecapeptide BPC 157 therapy by activation of collateral pathways counteracted various occlusion/occlusion-like syndromes, vascular, and multiorgan failure, and blood pressure disturbances in rats with permanent major vessel occlusion and similar procedures disabling endothelium function. Thereby, we revealed BPC 157 cytoprotective therapy with strong vascular rescuing capabilities in glaucoma therapy. With these capabilities, BPC 157 therapy can recover glaucomatous rats, normalize intraocular pressure, maintain retinal integrity, recover pupil function, recover retinal ischemia, and corneal injuries (i.e., maintained transparency after complete corneal abrasion, corneal ulceration, and counteracted dry eye after lacrimal gland removal or corneal insensitivity). The most important point is that in glaucomatous rats (three of four episcleral veins cauterized) with high intraocular pressure, all BPC 157 regimens immediately normalized intraocular pressure. BPC 157-treated rats exhibited normal pupil diameter, microscopically well-preserved ganglion cells and optic nerve presentation, normal fundus presentation, nor- mal retinal and choroidal blood vessel presentation, and normal optic nerve presentation. The one episcleral vein rapidly upgraded to accomplish all functions in glaucomatous rats may correspond with occlusion/occlusion-like syndromes of the activated rescuing collateral pathway (azygos vein direct blood flow delivery). Normalized intraocular pressure in glaucomatous rats corresponded to the counteracted intra-cranial (superior sagittal sinus), portal, and caval hypertension, and aortal hypotension in occlusion/occlusion-like syndromes, were all attenuated/eliminated by BPC 157 therapy. Furthermore, given in other eye disturbances (i.e., retinal ischemia), BPC 157 instantly breaks a noxious chain of events, both at an early stage and an already advanced stage. Thus, we further advocate BPC 157 as a therapeutic agent in ocular disease.

Acute central retinal artery occlusion with emboli

CRAO is an ophthalmic and medical emergency. This case is a reminder that diagnosis and management of CRAO begins with ophthalmologists but immediately thereafter care involves emergency cardiovascular and neurological similar to cerebral stroke.

Ocular Manifestations of Takayasu's Arteritis-A Case-Based Systematic Review and Meta-Analysis

Takayasu's arteritis (TA) is a type of vasculitis in which inflammation develops in large vessels, especially in the aorta and its branches. Our study aims to determine the prevalence and type of ocular manifestations in TA. A systematic literature search was conducted in December 2022 using three electronic databases (PubMed, Scopus, and Web of Science). The following data were extracted from each article: the name of the first author; the patient's age, sex, and origin (continent); circumstances connected with the diagnosis of TA; symptoms given by the patients; reported ocular manifestations; and administered treatment. The final analysis was based on data collected from 122 cases. Retinal ischemia, followed by optic neuropathy, cataract, and retinal artery occlusion, were the most prevalent eye conditions associated with the disease. Systemic steroid therapy, vascular procedures, and methotrexate were mainly used to treat pulseless disease. Patients mostly complained of gradual vision acuity loss, sudden vision acuity loss, ocular pain, and amaurosis fugax. The diagnosis of Takayasu's arteritis should be considered in patients presenting symptoms of visual decline/loss, ocular pain, or signs of retinal ischemia, optic neuropathy, or early cataract formation. A proper diagnosis is crucial to ensure the patient receives treatment without significant delay.

Melatonin Alleviates Retinal Ischemia-Reperfusion Injury by Inhibiting p53-Mediated Ferroptosis

Retinal ischemia-reperfusion (RIR) injury caused by high intraocular pressure (IOP) is an important risk factor contributing to retinal ganglion cell (RGC) death, eventually causing blindness. A key progressive pathological process in the development of RIR is the death of RGCs. However, the detailed mechanisms underlying RGC death caused by RIR have not yet been clearly elucidated, and effective treatments are lacking. Ferroptosis is a recently defined form of programmed cell death that is closely related to organ injury. Melatonin (MT) is a promising neuroprotective agent, but its effects on RIR injury remain unclear. In this study, murine models of acute ocular hypertension and oxygen and glucose deprivation/reoxygenation (OGD/R) model were adopted to simulate retinal ischemia. MT alleviated retinal damage and RGC death in RIR mice, significantly attenuating RIR-induced ferroptosis. Furthermore, MT reduced the expression of p53, a master regulator of ferroptosis pathways, and the upregulation of p53 promoted ferroptosis and largely abolished the neuroprotective effects of MT. Mechanistically, the overexpression (OE) of p53 suppressed the expression of the solute carrier family 7 member 11 (Slc7a11), which was accompanied by increased 12-lipoxygenase (Alox12) expression, triggering retinal ferroptosis. Moreover, MT-ameliorated apoptosis, neuroinflammation and microglial activation were observed. In summary, MT conferred neuroprotection against RIR injury by inhibiting p53-mediated ferroptosis. These findings indicate that MT is a retina-specific ferroptosis inhibitor and a promising therapeutic agent for retinal neuroprotection.

Neuroprotective Effect of a Nutritional Supplement Containing Spearmint Extract, Forskolin, Homotaurine and Group B Vitamins in a Mouse Model of Transient Ocular Hypertension

Glaucoma is one of the most common sight-threatening eye disorders and one of the main causes of irreversible blindness worldwide. The current therapies focusing on reducing intraocular pressure (IOP) are often insufficient to prevent the progression of the disease, so the therapeutic management of glaucoma remains a challenge. The aim of this study was to evaluate the neuroprotective, IOP-lowering independent effects of a nutritional supplement containing forskolin, homotaurine, spearmint extract and vitamins of the B group in a model of acute glaucoma developed in mice. Glaucoma was induced in adult wild-type C57BL/6J mice by transient elevation of IOP. The dietary supplement, branded as Gangliomix^® (125 mg/kg/day), was administered by oral gavage for 17 days and ocular hypertension was induced on the 10th day of treatment. A histological analysis of the retinas was performed and RGC survival was evaluated with fluorogold labeling and Brn3a immunostaining on wholemount and retinal sections. Expression of alpha-spectrin, caspase-3, PARP-1 and GFAP was studied with western blotting or immunofluorescence. A significant increase in RGC survival was reported in the retina of mice treated with the dietary supplement as compared to vehicle-treated animals. The observed neuroprotection was associated with a calpain activity decrease, reduction in caspase-3 and PARP-1 activation, and prevention of GFAP upregulation. These effects were independent from the hypotensive effects of the supplement. Altogether, our data suggest that the dietary supplementation with forskolin, homotaurine, spearmint extract and vitamins of the B group supports RGC survival and may offer beneficial effects in glaucoma patients in combination with the currently used IOP-lowering therapy.

The Impact of Intraocular Treatment on Visual Acuity of Patients Diagnosed with Branch Retinal Vein Occlusions

Branch retinal vein occlusions are a significant cause of vision loss and present several ophthalmic and systemic risk factors, including age, hypertension, hyperlipidemia and glaucoma. Retinal vein occlusion is the second-most-common retinal vascular disease. This study evaluated the effects of Ozurdex in contrast to a combination therapy with anti-vascular endothelial growth factor (VEGF) and cortisone in treatment-naive branch retinal vein occlusions-macular edema (BRVO-ME) cases, at 4-month and 6-month follow-ups. Thirty eyes were included in the study, which were divided into two groups. The first group consisted of 15 eyes, and each received 1 injection of dexamethasone intravitreal implant Ozurdex (DEX). The second group of 15 eyes received 3 intravitreal injections, the first and second with the anti-vascular endothelial growth factor aflibercept and the third one with 4 mg of triamcinolone acetonide (Vitreal S), spaced at one month. The best corrected visual acuity (BCVA) results suggested that the peak efficacy was at 4 months for both groups, with mean values of 0.5 LogMAR and 0.4 LogMAR. Regarding macular edema, there were no significant changes between the 4- and 6-month follow-up periods, with mean values of 361 μm and 390 μm. Six patients experienced transient raised intraocular pressure at one week after treatment. This study highlights the benefits to visual acuity of the combination of anti-vascular endothelial growth factor and cortisone, which represents a viable solution with similar results to Ozurdex therapy.

Natural products: protective effects against ischemia-induced retinal injury

Ischemic retinal damage, a common condition associated with retinal vascular occlusion, glaucoma, diabetic retinopathy, and other eye diseases, threatens the vision of millions of people worldwide. It triggers excessive inflammation, oxidative stress, apoptosis, and vascular dysfunction, leading to the loss and death of retinal ganglion cells. Unfortunately, minority drugs are available for treating retinal ischemic injury diseases, and their safety are limited. Therefore, there is an urgent need to develop more effective treatments for ischemic retinal damage. Natural compounds have been reported to have antioxidant, anti-inflammatory, and antiapoptotic properties that can be used to treat ischemic retinal damage. In addition, many natural compounds have been shown to exhibit biological functions and pharmacological properties relevant to the treatment of cellular and tissue damage. This article reviews the neuroprotective mechanisms of natural compounds involve treating ischemic retinal injury. These natural compounds may serve as treatments for ischemia-induced retinal diseases.

Coincident Acute Macular Neuroretinopathy and Paracentral Acute Middle Maculopathy in COVID-19

An ophthalmology consultation was requested for a 29-year-old woman complaining of visual field defects. The patient had presented to the emergency department with cough and high fever one day earlier. Chest computed tomography demonstrated pneumonia and two severe acute respiratory syndrome coronavirus 2 polymerase chain reaction tests were positive. The patient had undergone renal transplantation 11 years ago due to glomerulonephritis. Best-corrected visual acuity (BCVA) was 20/40 in the right eye and 20/30 in the left eye. Fluorescein angiography showed macular hypoperfusion, and optical coherence tomography (OCT) showed hyperreflectivity in the inner nuclear, outer plexiform, and outer nuclear layers, as well as discontinuity of the ellipsoid zone. Perimetry confirmed bilateral central scotoma. Levels of D-dimer and fibrinogen were 0.86 g/mL and 435.6 g/mL, respectively. The patient was diagnosed as having concurrent acute macular neuroretinopathy and paracentral acute middle maculopathy and was given low-molecular-weight heparin treatment for one month. Her BCVA improved to 20/20 in both eyes, and regression was observed in the retinal findings, hyperreflectivity and ellipsoid zone disruption on OCT, and scotoma in perimetry. Inflammation, thrombosis, and glial involvement may play a role in the pathogenesis of retinal microvascular impairment in COVID-19.

Aflibercept for the Treatment of Macular Edema Secondary to Idiopathic Retinal Vasculitis, Aneurysms, and Neuroretinitis Syndrome

We report a case of idiopathic retinal vasculitis, aneurysms, and neuroretinitis (IRVAN) syndrome in a patient whose cystoid macular edema (CME) was successfully treated with aflibercept and pan-retinal photocoagulation (PRP). A 56-year-old male was sent to our uveitis service for further evaluation after a fluorescein angiogram revealed symmetric retinal ischemia for 360 degrees in both eyes. A fundus examination revealed an aneurysm, neuroretinitis, and occlusive vasculitis, all consistent with a diagnosis of IRVAN syndrome. An optical coherence tomography examination revealed CME of the left eye. A chest X-ray revealed minimally prominent interstitial markings. The patient had a positive QuantiFERON-TB Gold test and was treated for tuberculosis with a one-year course of isoniazid and pyrimethamine. A further workup for other infectious and autoimmune etiologies was negative. The initial treatment consisted of bilateral PRP of the areas of peripheral ischemia, treatment for which was provided in a fragmented fashion over the course of seven months. Soon after the diagnosis, he received treatment with two intravitreal injections of aflibercept (2 mg/0.5 mL), one month apart, to the left eye. Subsequently, four months following the presentation, he developed CME in the right eye, which was treated with a single intravitreal injection of aflibercept (2 mg/0.5 mL). At his last follow-up visit, four years after the initial presentation, the patient remained asymptomatic with 20/20 visual acuity in both eyes and no evidence of CME recurrence. Our case suggests that aflibercept may serve as an adjuvant to the standard treatment with PRP, especially in cases that present with associated macular edema.

Paracentral Acute Middle Maculopathy Associated with Severe Anti-Mog (Myelin Oligodendrocyte Glycoprotein)-Positive Optic Neuritis

Retinal complications in patients with inflammatory optic neuritis (ON) are generally related to post-infectious neuroretinitis and are considered uncommon in autoimmune/demyelinating ON, whether isolated or caused by multiple sclerosis (MS) or neuromyelitis optica spectrum disorder (NMOSD). More recently, however, cases with retinal complications have been reported in subjects positive for myelin oligodendrocyte glycoprotein (MOG) antibodies. We report a 53-year-old woman presenting with severe bilateral ON associated with a focal area of paracentral acute middle maculopathy (PAMM) in one eye. Visual loss recovered remarkably after high-dose intravenous corticosteroid treatment and plasmapheresis, but the PAMM lesion remained visible on both optical coherence tomography and angiography as an ischaemic lesion affecting the middle layers of the retina. The report emphasises the possible occurrence of retinal vascular complications in MOG-related optic neuritis, an important addition to the diagnosis of, and possible differentiation from, MS-related or NMOSD-related ON.

A Nonrandomized Phase 2 Trial of EG-Mirotin, a Novel, First-in-Class, Subcutaneously Deliverable Peptide Drug for Nonproliferative Diabetic Retinopathy

Background and objectives: EG-Mirotin (active ingredient EGT022) targets nonproliferative diabetic retinopathy (NPDR), the early stage of retinopathy. EG-Mirotin reverses capillary damage before NPDR progresses to an irreversible stage. EG-Mirotin safety and efficacy were investigated in patients with type 1 or type 2 diabetes mellitus and moderate to severe NPDR. Methods: In this open-label, single-arm, single-center, exploratory phase II study, 10 patients (20 eyes) received EG-Mirotin once a day (3 mg/1.5 mL sterile saline) for 5 days and were evaluated for ischemic index changes and safety. End of study was approximately 8 ± 1 weeks (57 ± 7 days) after the first drug administration. Results: EG-Mirotin injections were well tolerated, with no dose-limiting adverse events, serious adverse events, or deaths. Four treatment-emergent adverse events (TEAEs) unrelated to the investigational drug were observed in 2 out of 10 participants (20%) who had received the investigational drug. The overall average percent change in ischemic index at each evaluation point compared with baseline was statistically significant (Greenhouse-Geisser F = 9.456, p = 0.004 for the main effect of time), and a larger change was observed when the baseline ischemic index value was high (Greenhouse-Geisser F = 10.946, p = 0.002 for time × group interaction). Conclusions: The EG-Mirotin regimen established in this study was shown to be feasible and safe and was associated with a trend toward potential improvement in diabetes-induced ischemia and retinal capillary leakage.

A Review of Neovascular Glaucoma: Etiology, Pathogenesis, Diagnosis, and Treatment

Neovascular glaucoma (NVG) is a rare, aggressive, blinding secondary glaucoma, which is characterized by neovascularization of the anterior segment of the eye and leading to elevation of the intraocular pressure (IOP). The main etiological factor is retinal ischemia leading to an impaired homeostatic balance between the angiogenic and antiangiogenic factors. High concentrations of vasogenic substances such as vascular endothelial growth factor (VEGF) induce neovascularization of the iris (NVI) and neovascularization of the angle (NVA) that limits the outflow of aqueous humor from the anterior chamber and increases the IOP. NVG clinical, if untreated, progresses from secondary open-angle glaucoma to angle-closure glaucoma, leading to irreversible blindness. It is an urgent ophthalmic condition; early diagnosis and treatment are necessary to preserve vision and prevent eye loss. The management of NVG requires the cooperation of retinal and glaucoma specialists. The treatment of NVG includes both control of the underlying disease and management of IOP. The main goal is the prevention of angle-closure glaucoma by combining panretinal photocoagulation (PRP) and antiangiogenic therapy. The aim of this review is to summarize the current available knowledge about the etiology, pathogenesis, and symptoms of NVG and determine the most effective treatment methods.

Nicotinamide Mononucleotide Protects against Retinal Dysfunction in a Murine Model of Carotid Artery Occlusion

Cardiovascular abnormality-mediated retinal ischemia causes severe visual impairment. Retinal ischemia is involved in enormous pathological processes including oxidative stress, reactive gliosis, and retinal functional deficits. Thus, maintaining retinal function by modulating those pathological processes may prevent or protect against vision loss. Over the decades, nicotinamide mononucleotide (NMN), a crucial nicotinamide adenine dinucleotide (NAD⁺) intermediate, has been nominated as a promising therapeutic target in retinal diseases. Nonetheless, a protective effect of NMN has not been examined in cardiovascular diseases-induced retinal ischemia. In our study, we aimed to investigate its promising effect of NMN in the ischemic retina of a murine model of carotid artery occlusion. After surgical unilateral common carotid artery occlusion (UCCAO) in adult male C57BL/6 mice, NMN (500 mg/kg/day) was intraperitoneally injected to mice every day until the end of experiments. Electroretinography and biomolecular assays were utilized to measure ocular functional and further molecular alterations in the retina. We found that UCCAO-induced retinal dysfunction was suppressed, pathological gliosis was reduced, retinal NAD⁺ levels were preserved, and the expression of an antioxidant molecule (nuclear factor erythroid-2-related factor 2; Nrf2) was upregulated by consecutive administration of NMN. Our present outcomes first suggest a promising NMN therapy for the suppression of cardiovascular diseases-mediated retinal ischemic dysfunction.

Mitochondrial Dysfunction in a High Intraocular Pressure-Induced Retinal Ischemia Minipig Model

Purpose: Retinal ischemia (RI) and progressive neuronal death are sight-threatening conditions. Mitochondrial (mt) dysfunction and fusion/fission processes have been suggested to play a role in the pathophysiology of RI. This study focuses on changes in the mt parameters of the neuroretina, retinal pigment epithelium (RPE) and choroid in a porcine high intraocular pressure (IOP)-induced RI minipig model. Methods: In one eye, an acute IOP elevation was induced in minipigs and compared to the other control eye. Activity and amount of respiratory chain complexes (RCC) were analyzed by spectrophotometry and Western blot, respectively. The coenzyme Q10 (CoQ10) content was measured using HPLC, and the ultrastructure of the mt was studied via transmission electron microscopy. The expression of selected mt-pathway genes was determined by RT-PCR. Results: At a functional level, increased RCC I activity and decreased total CoQ10 content were found in RPE cells. At a protein level, CORE2, a subunit of RCC III, and DRP1, was significantly decreased in the neuroretina. Drp1 and Opa1, protein-encoding genes responsible for mt quality control, were decreased in most of the samples from the RPE and neuroretina. Conclusions: The eyes of the minipig can be considered a potential RI model to study mt dysfunction in this disease. Strategies targeting mt protection may provide a promising way to delay the acute damage and onset of RI.

Silencing of circular RNA‑ZYG11B exerts a neuroprotective effect against retinal neurodegeneration

Ischemic retinal diseases are the major cause of vision impairment worldwide. Currently, there are no available treatments for ischemia‑induced retinal neurodegeneration. Circular RNAs (circRNAs) have emerged as important regulators of several biological processes and human diseases. The present study investigated the role of circRNA‑ZYG11B (circZYG11B; hsa_circ_0003739) in retinal neurodegeneration. Reverse transcription quantitative polymerase chain reaction (RT‑qPCR) demonstrated that circZYG11B expression was markedly increased during retinal neurodegeneration in vivo and in vitro. Cell Counting Kit‑8, TUNEL and caspase‑3 activity assays revealed that silencing of circZYG11B was able to protect against oxidative stress‑ or hypoxic stress‑induced retinal ganglion cell (RGC) injury. Furthermore, immunofluorescence staining and hematoxylin and eosin staining revealed that silencing of circZYG11B alleviated ischemia/reperfusion‑induced retinal neurodegeneration, as indicated by reduced RGC injury and decreased retinal reactive gliosis. In addition, luciferase reporter, biotin‑coupled miRNA capture and RNA immunoprecipitation assays revealed that circZYG11B could regulate RGC function through circZYG11B/microRNA‑620/PTEN signaling. Clinically, RT‑qPCR assays demonstrated that circZYG11B expression was markedly increased in the aqueous humor of patients with glaucoma. In conclusion, circZYG11B may be considered a promising target for the diagnosis and treatment of retinal ischemic diseases.

Presentation, etiology and treatment outcome of neovascular glaucoma in Ekiti state, South Western Nigeria

Background

Neovascular glaucoma (NVG), a form of secondary glaucoma has varying causes across geographical locations.

Objective

The objective of this study was to determine the presentation, aetiology, and outcome of treatment of patients with NVG in a Nigerian tertiary hospital.

Method

A retrospective review of records of all cases of NVG seen over a 5year period was carried out. Demographic characteristics, presenting visual acuity and coexisting ocular and systemic conditions were noted. Data were analysed with Statistical Package for Social Sciences (SPSS) version 25.

Results

29 eyes of patients with NVG were analysed. Most of the patients (89.70%) presented with visual acuity less than 3/60 in the affected eye. All patients except one were treated with anti-glaucoma medications while only 9(31%) consented to and received anti-vascular endothelial growth factor. No patient had improvement in visual acuity despite resolution of other symptoms at 12week follow up.

Conclusion

NVG though not as common as other forms of glaucoma accounted for a large proportion of monocular blindness in the affected eyes at presentation. There is need for health promotion and education among our people on the need for early preventive eye check practices.

Pemafibrate Prevents Retinal Dysfunction in a Mouse Model of Unilateral Common Carotid Artery Occlusion

Cardiovascular diseases lead to retinal ischemia, one of the leading causes of blindness. Retinal ischemia triggers pathological retinal glial responses and functional deficits. Therefore, maintaining retinal neuronal activities and modulating pathological gliosis may prevent loss of vision. Previously, pemafibrate, a selective peroxisome proliferator-activated receptor alpha modulator, was nominated as a promising drug in retinal ischemia. However, a protective role of pemafibrate remains untouched in cardiovascular diseases-mediated retinal ischemia. Therefore, we aimed to unravel systemic and retinal alterations by treating pemafibrate in a new murine model of retinal ischemia caused by cardiovascular diseases. Adult C57BL/6 mice were orally administered pemafibrate (0.5 mg/kg) for 4 days, followed by unilateral common carotid artery occlusion (UCCAO). After UCCAO, pemafibrate was continuously supplied to mice until the end of experiments. Retinal function (a-and b-waves and the oscillatory potentials) was measured using electroretinography on day 5 and 12 after UCCAO. Moreover, the retina, liver, and serum were subjected to qPCR, immunohistochemistry, or ELISA analysis. We found that pemafibrate enhanced liver function, elevated serum levels of fibroblast growth factor 21 (FGF21), one of the neuroprotective molecules in the eye, and protected against UCCAO-induced retinal dysfunction, observed with modulation of retinal gliosis and preservation of oscillatory potentials. Our current data suggest a promising pemafibrate therapy for the suppression of retinal dysfunction in cardiovascular diseases.

Protection of Retinal Function by Nucleoside Reverse Transcriptase Inhibitors Following Retinal Ischemia/Reperfusion Injury

Purpose: Retinal ischemia/reperfusion (I/R) injury is a common cause of visual impairment and blindness for which there remain limited treatment options. Nucleoside reverse transcriptase inhibitors (NRTIs), such as zidovudine (AZT), have been shown to block the NLRP3 inflammasome and prevent retinal degeneration in a mouse model of age-related macular degeneration. The NLRP3 inflammasome has also been shown to be triggered in I/R injury. Therefore, we studied the neuroprotective effects of AZT using a pressure-induced retinal ischemia mouse model. Methods: C57BL/6J mice were randomly assigned to 1 of 2 treatment groups: vehicle-treated retinal I/R injury (n = 6) or AZT-treated retinal I/R injury (n = 6). Vehicle (1% dimethyl sulfoxide [DMSO] in phosphate-buffered saline [PBS]) or AZT 50 mg/kg in 1% DMSO in PBS were injected intraperitoneally twice daily for 5 days. On day 2 of treatment, retinal ischemia was induced by transient elevation of intraocular pressure for 45 min. Scotopic electroretinography (ERG) was used to quantify retinal function before and 1 week after retinal ischemic insult. Retinal morphology was examined 1 week after ischemic insult. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assays and caspase 1 immunostaining was performed 24 h after retinal I/R injury. Results: Following I/R injury, ERG a- and b-wave amplitudes were significantly reduced in the vehicle-treated mice. AZT treatment significantly attenuated I/R-induced loss of retinal function as compared with vehicle-treated mice. Additionally, AZT-treated mice experienced significantly less inner retinal thinning as compared with vehicle-treated mice. TUNEL-positive cells were prevalent in the vehicle-treated I/R injury mouse retinas compared with the AZT-treated I/R injury mouse retinas. More caspase-1 immunoreactivity was detected in ganglion cell layer and inner nuclear layer (INL) in vehicle-treated I/R injury group than in AZT-treated I/R injury group. Conclusion: AZT treatment resulted in relative preservation of retinal structure and function following ischemic insult as compared with controls. This suggests AZT may have therapeutic value in the management of retinal ischemic diseases.

Inhibition of the HIF-1α/BNIP3 pathway has a retinal neuroprotective effect

Retinal ischemia is a leading cause of irreversible blindness worldwide. Inner retinal dysfunction including loss of retinal ganglion cells is encountered in a number of retinal ischemic disorders. We previously reported administration of two different hypoxia-inducible factor (HIF) inhibitors exerted neuroprotective effects in a murine model of retinal ischemia/reperfusion (I/R) which mimics these disorders, as inner retinal degeneration could be involved in pathological HIF induction. However, this notion needs further investigation. Therefore, in this study, we attempted to use retina-specific Hif-1α conditional knockout (cKO) mice to uncover this notion more clearly under the same condition. Hif-1α cKO mice showed inner retinal neurodegeneration to a lesser extent than control mice. Hif-1α depletion in a murine 661W retinal cell line reduced cell death under pseudohypoxic and hypoxic conditions. Among hypoxia-related genes, the expression of BCL2 19 kDa protein-interacting protein 3 (Bnip3) was substantially upregulated in the inner retinal layer after retinal I/R. In this regard, we further examined Bnip3 depletion in retinal neurons in vitro and in vivo and found the similar neuroprotective effects. Our results support the notion that the HIF-1α/BNIP3 pathway may have a critical role in inner retinal neurodegeneration, which can be linked with the development of new promising therapeutics for inner retinal ischemic disorders.

Neovascular glaucoma - A review

Neovascular glaucoma (NVG) is a sight-threatening secondary glaucoma characterized by appearance of new vessels over the iris and proliferation of fibrovascular tissue in the anterior chamber angle. Retinal ischemia is the common driving factor and common causes are central retinal vein occlusion, proliferative diabetic retinopathy, and ocular ischemic syndrome. The current rise in the prevalence of NVG is partly related to increase in people with diabetes. A high index of suspicion and a thorough anterior segment evaluation to identify the early new vessels on the iris surface or angle are essential for early diagnosis of NVG. With newer imaging modalities such as the optical coherence tomography angiography and newer treatment options such as the anti-vascular endothelial growth factor, it is possible to detect retinal ischemia early, tailor appropriate treatment, monitor disease progression, and treatment response. The management strategies are aimed at reducing the posterior segment ischemia, reduce the neovascular drive, and control the elevated intraocular pressure. This review summarizes the causes, pathogenesis, and differential diagnoses of NVG, and the management guidelines. We also propose a treatment algorithm of neovascular glaucoma.

Simultaneous Bilateral Central Retinal Artery Occlusion following COVID-19 Infection

Purpose: Coronavirus-19 disease (COVID-19) has been associated with a high risk of thrombotic complications. Here, we report the case of a patient who developed simultaneous bilateral retinal artery occlusion following COVID-19 infection.Case Report: A 42-year-old male with no systemic co-morbidities presented with sudden, painless loss of vision in both eyes. Fundoscopy showed retinal edema and cherry-red spots in both eyes. Fluorescein angiography showed reperfusion, absence of choroidal ischemia, and Optical Coherence Tomography showed thickened inner retinal layers suggestive of retinal edema and the outer retinal layers appeared intact. Blood investigations for vasculitis, coagulation profile, lipids, and homocysteine level were within normal limits.Conclusion: COVID-19 patients may develop a systemic coagulopathy and acquired thrombophilia characterized by a tendency for venous, arterial, and microvascular thrombosis. This hypercoagulable state is believed to be a hyperinflammatory response; physicians and ophthalmologists, alike, should be aware of these possible long-term sequelae.

Development of neovascular glaucoma after intraocular surgery in Pierson syndrome

Purpose: To report a patient with Pierson syndrome who presented with neovascular glaucoma (NVG) after cataract surgery.Methods: Retrospective case report.Results: A 17-year old monocular female presented with sudden onset of pain and decreased vision in the right eye. On examination, she had intraocular pressure (IOP) of 50 mmHg, aggressive iris neovascularization (NVI) and 3-piece IOL. Fundus examination revealed pale disc with tessellated fundus and parapapillary atrophy. Vascular arcades were vertically stretched with avascular ischemic retina starting from the near periphery. Macula appeared thin and atrophic. An intravitreal injection of 0.05 mg/0.1 ml bevacizumab was given to the right eye followed by Ahmed glaucoma valve (AGV) implantation. Assessment of her brother revealed similar posterior segment changes. A subsequent urine analysis showed proteinuria and high albumin to creatinine ratio. Next-generation sequencing for LAMB2 gene revealed a homozygous c.4573 + 1 G > A variant confirming the diagnosis of Pierson syndrome.Conclusion: This case expands our knowledge on retinal ischemia in the setting of Pierson syndrome. Close monitoring after intraocular surgery is recommended to look for the development of NVG.

The neuroprotective effect of submicron and blended Lycium barbarum for experiment retinal ischemia and reperfusion injury in rats

The purpose of this study was to investigate the neuroprotective potential of submicron (milled) and blended Lycium barbarum (LB) in glaucomatous retinal neuropathy using a rat model of high intraocular pressure (HIOP) induced retinal ischemia. The rats were treated with 500, 250, 100 mg/kg LB (submicron or blended form) orally once daily for 56 days respectively after 1 week of retinal ischemia induction. We conducted electroretinography (ERG), histopathological analysis in retina and antioxidative level assays, such as total glutathione (GSH (glutathione) + reduced glutathione) + GSSH (glutathione disulfide), catalase activity, SOD (superoxide dismutase) activity, and lipid peroxidant malondialdehyde (MDA) in the retina and plasma of test rats. The results indicated that the amplitudes of a and b wave of ERG were preserved in rats treated with submicron and blended LB groups, the best protective effect on ERG b wave amplitudes was observed at the dosage of 250 mg/kg of both forms of LB. Retinal thickness was best preserved, particularly significant in the retinal inner nuclear layer in submicron 250 mg/kg LB group. The levels of antioxidant GSSH+GSH, SOD and catalase activity in the retina were higher in blended 500 mg/kg and submicron 250 mg/kg groups than other groups, while the MDA level was lower in submicron LB groups than that in blended LB and non-LB IR group. In the plasma, there was no significant difference in the levels of GSSH+GSH and catalase activity between treated groups, but higher levels of SOD and lower levels of MDA were observed in 250 mg/kg submicron and 500 mg/kg submicron LB groups than the blended LB and non-LB IR groups. Generally better antioxidative effects were observed in the submicron LB than blended LB among treated groups, especially the 250 mg/kg submicron LB, providing good retinal neuroprotection by preserving retinal structure and function with improved antioxidative capacity. The submicron LB may have clinical implication as an adjuvant therapy of oxidative stress and retinal damage caused by HIOP induced retinal ischemia and reperfusion injury.

Contrast Sensitivity Testing in Retinal Vein Occlusion Using a Novel Stimulus

Purpose

This study evaluated a novel tool known as the motion diamond stimulus (MDS), which utilizes contrast-generated illusory motion in dynamic test regions to determine contrast sensitivity (CS).

Methods

Patients with treated unilateral retinal vein occlusions (RVOs) underwent three assessments: the MDS, the Pelli-Robson (PR), and the National Eye Institute's Visual Function Questionnaire (VFQ-25). The MDS assessment produced two data end points, α and β. The α value represents the overall contrast threshold level and the β value serves to quantify the adaptability of the visual contrast system. The CS parameters from the MDS and log CS PR output values were used to compare RVO eyes (n = 20) to control eyes (n = 20).

Results

The study participants had a mean composite VFQ-25 score of 89.5 ± 10.4 on the VFQ-25. A significant difference was observed between the RVO eyes and the control eyes in PR log CS scores (P value = 0.0001) and in MDS α value (P value = 0.01). No difference in MDS β value was found between the study groups (P value = 0.39).

Conclusions

The results for the MDS assessment's α parameter corroborated the PR scores, suggesting contrast sensitivity threshold impairment in patients with RVO. No significant difference in β value was observed, suggesting that adaptability of the visual system is maintained in treated RVO eyes.

Translational Relevance

Currently, visual complaints cannot be entirely identified by Snellen visual acuity alone. The MDS offers potentially a more complete look at visual function, by including contrast sensitivity and may be able to quantify changes otherwise overlooked in retinal disease progression.

Stem Cells as Drug-like Biologics for Mitochondrial Repair in Stroke

Stroke is a devastating condition characterized by widespread cell death after disruption of blood flow to the brain. The poor regenerative capacity of neural cells limits substantial recovery and prolongs disruptive sequelae. Current therapeutic options are limited and do not adequately address the underlying mitochondrial dysfunction caused by the stroke. These same mitochondrial impairments that result from acute cerebral ischemia are also present in retinal ischemia. In both cases, sufficient mitochondrial activity is necessary for cell survival, and while astrocytes are able to transfer mitochondria to damaged tissues to rescue them, they do not have the capacity to completely repair damaged tissues. Therefore, it is essential to investigate this mitochondrial transfer pathway as a target of future therapeutic strategies. In this review, we examine the current literature pertinent to mitochondrial repair in stroke, with an emphasis on stem cells as a source of healthy mitochondria. Stem cells are a compelling cell type to study in this context, as their ability to mitigate stroke-induced damage through non-mitochondrial mechanisms is well established. Thus, we will focus on the latest preclinical research relevant to mitochondria-based mechanisms in the treatment of cerebral and retinal ischemia and consider which stem cells are ideally suited for this purpose.

Vascular Regeneration for Ischemic Retinopathies: Hope from Cell Therapies

Retinal vascular diseases, such as diabetic retinopathy, retinopathy of prematurity, retinal vein occlusion, ocular ischemic syndrome and ischemic optic neuropathy, are leading causes of vision impairment and blindness. Whilst drug, laser or surgery-based treatments for the late stage complications of many of these diseases are available, interventions that target the early vasodegenerative stages are lacking. Progressive vasculopathy and ensuing ischemia is an underpinning pathology in many of these diseases, leading to hypoperfusion, hypoxia, and ultimately pathological neovascularization and/or edema in the retina and other ocular tissues, such as the optic nerve and iris. Therefore, repairing the retinal vasculature may prevent progression of ischemic retinopathies into late stage vascular complications. Various cell types have been explored for their vascular repair potential. Endothelial progenitor cells, mesenchymal stem cells and induced pluripotent stem cells are studied for their potential to integrate with the damaged retinal vasculature and limit ischemic injury. Clinical trials for some of these cell types have confirmed safety and feasibility in the treatment of ischemic diseases, including some retinopathies. Another promising avenue is mobilization of endogenous endothelial progenitors, whereby reparative cells are moved from their niche to circulating blood to target and home into ischemic tissues. Several aspects and properties of these cell types have yet to be elucidated. Nevertheless, we foresee that cell therapy, whether through delivery of exogenous or enhancement of endogenous reparative cells, will become a valuable and beneficial treatment for ischemic retinopathies.

Retinoprotective Effect of 2-Ethyl-3-hydroxy-6-methylpyridine Nicotinate

An important task of pharmacology is to find effective agents to improve retinal microcirculation and resistance to ischemia. The purpose of the study is to pharmacologically evaluate the retinoprotective effect of 2-ethyl-3-hydroxy-6-methylpyridine nicotinate in a rat model of retinal ischemia–reperfusion. A retinal ischemia–reperfusion model was used, in which an increase in intraocular pressure (IOP) to 110 mmHg was carried out within 30 min. The retinoprotective effect of 2-ethyl-3-hydroxy-6-methylpyridine nicotinate at a dose of 3.8 mg/kg, in comparison with nicotinic acid at a dose of 2 mg/kg and emoxipine at a dose of 2 mg/kg, was estimated by the changes in the eye fundus during ophthalmoscopy, the retinal microcirculation level with laser Doppler flowmetry (LDF), and electroretinography (ERG) after 72 h of reperfusion. The use of 2-ethyl-3-hydroxy-6-methylpyridine nicotinate prevented the development of ischemic injuries in the fundus and led to an increase in the retinal microcirculation level to 747 (median) (lower and upper quartiles: 693;760) perfusion units (p = 0.0002) in comparison with the group that underwent no treatment. In the group with the studied substance, the b-wave amplitude increased significantly (p = 0.0022), and the b/a coefficient increased reliably (p = 0.0002) in comparison with the group with no treatment. Thus, 2-ethyl-3-hydroxy-6-methylpyridine nicotinate has established itself as a potential retinoprotector.

Risk of Stroke in Patients With Ocular Arterial Occlusive Disorders: A Retrospective Canadian Study

Background

Monocular vision loss, attributed to either central retinal artery occlusion (CRAO), branch retinal artery occlusion (BRAO), or ocular ischemic syndrome (OIS), is thought to be associated with an increased prevalence of cerebral infarcts. However, there is a paucity of data substantiating this. We aimed to investigate this relationship in a Canadian center and further understand the importance of associated internal carotid artery stenosis in potential clinical decision making.

Methods and Results

We performed a retrospective cohort study at a comprehensive stroke center of patients presenting initially with CRAO, BRAO, or OIS to a centralized ophthalmology center over a 5‐year period. Patients were followed for 3 years for the occurrence of a hemispheric stroke. We identified 83 affected eyes, with 31 CRAO, 35 BRAO, and 17 OIS patients. Before ocular diagnosis, 32.3%, 11.4%, and 41.2% of CRAO, BRAO, and OIS patients, respectively, experienced a symptomatic stroke. Of the remaining patients, 4.8%, 12.9%, and 40%, respectively, suffered a hemispheric stroke within 3 years of ocular diagnosis. Logistic regressions suggested that for CRAO and BRAO patients together, the degree of ipsilateral internal carotid artery stenosis is unable to predict the occurrence of a stroke (P=0.18), whereas our model correctly predicted a stroke in 82.4% of OIS patients (P=0.005).

Conclusions

CRAO, BRAO, and OIS are associated with significantly increased symptomatic stroke rates. Degree of ipsilateral internal carotid artery stenosis may not be useful in risk stratification for these patients, suggesting that they should be triaged appropriately for stroke risk‐factor management, independent of internal carotid artery stenosis.

Mbd2 Mediates Retinal Cell Apoptosis by Targeting the lncRNA Mbd2-AL1/miR-188-3p/Traf3 Axis in Ischemia/Reperfusion Injury

Recent studies reported that DNA methylation was involved in retinal cell death. Methyl-CpG binding domain protein 2 (Mbd2) is one of the DNA methylation readers. Its role and mechanism of regulation remain unclear. The ischemia/reperfusion (I/R) model in mice primary culture retinal ganglion cells (RGCs) and Mbd2 knockout (Mbd2-KO) mice was used in the current study. We demonstrated that Mbd2 mediates RGC apoptosis caused by I/R injury. Mechanistically, the data suggested that Mbd2 upregulated Mbd2-associated long noncoding RNA 1 (Mbd2-AL1) via demethylation of its promoter. Furthermore, Mbd2-AL1 sponged microRNA (miR)-188-3p, thus preventing tumor necrosis factor (TNF) receptor-associated factor 3 (Traf3) downregulation and inducing RGC apoptosis. This was further demonstrated by the fact that inhibition of miR-188-3p diminished the anti-apoptosis role of Mbd2-AL1 small interfering RNA (siRNA). Finally, it showed that the apoptosis of retinal cells was attenuated, and the visual function was preserved in Mbd2-KO mice, which were associated with the Mbd2-AL1/miR-188-3p/Traf3 axis. Our present study revealed the role of Mbd2 in RGC apoptosis, which may provide a novel therapeutic strategy for retinal ischemic diseases.

Peripheral retinal neovascularization in a patient with pilocytic astrocytoma

We described a case of papilledema complicated by peripheral retinal vessels in a 12-year-old boy affected by cerebellar astrocytoma. Opportunity to treat with photocoagulation or intravitreal anti-VEGF (vascular endothelial growth factor) injections was discussed with the parents and no treatment was done. After 5 years from surgery, retinal neovascularization was stable without vitreal hemorrhages or retinal complications, more specifically fibrosis of the neovessels increased and leakage phenomena were reduced at the fluorescein angiography. To our knowledge, this is a unique case of papilledema complicated by peripheral retinal vessels in a patient affected by cerebellar astrocytoma.

Animal Models Used to Simulate Retinal Artery Occlusion: A Comprehensive Review

Purpose

To present an overview of animal models of retinal artery occlusion (RAO).

Methods

Through a systematic literature search in PubMed and Embase, papers describing methods of inducing RAO in animal models were included. The identified methodologic approaches were presented in a narrative synthesis and compared with RAO in humans.

Results

In total, 83 papers reporting on 88 experiments were included. Six different species were used with rodents and monkeys being the most common, and a minority were performed using cats, dogs, rabbits, or pigs. The anatomy of pigs and monkeys resemble that of humans most closely. The two most frequently used methods were laser-induced occlusion or ligation of the arteries. Other methods included raised intraocular pressure, arterial clamping, administration of vasoconstricting agents, the use of an occluder, embolization, and endovascular approaches to induce occlusion. In general, occlusions lasted for only 30 to 90 minutes, often followed by reperfusion.

Conclusions

Although a broad range of methods have previously been used, they all have limitations. Preferably, the methods should imitate the human disease as closely as possible and avoid damaging other structures. Therefore, monkeys followed by pigs are to be preferred and ligation or clamping may be a suitable model in larger animals as there is a potential to isolate and occlude the retinal artery only. Being less invasive, laser-induced occlusion is another suitable approach.

Translational Relevance

This review aims at assisting researchers in deciding on the most ideal experimental setting, and thereby increase the translational value to human disease.

Correction of Experimental Retinal Ischemia by l-Isomer of Ethylmethylhydroxypyridine Malate

An important task of pharmacology and ophtalmology is to find specific and highly effective agents for correcting retinal ischemia. The objective of this study is to increase the effectiveness of pharmacological correction of retinal ischemia by using new 3-hydroxypyridine derivative–l-isomer of ethylmethylhydroxypyridine malate. A modification to the retinal ischemia-reperfusion model was used, in which an increase in intraocular pressure is carried out by mechanical pressure (110 mmHg) to the front chamber of the eye for 30 min. The protective effects of l-isomer of ethylmethylhydroxypyridine malate in comparison with Emoxipine as pretreatment, with parabulbar injection, based on the model of retinal ischemia-reperfusion, were estimated by the changes in the ratio of the amplitudes of the a- and b-waves of electroretinography (the b/a coefficient) and ophthalmoscopy. The use of l-isomer of ethylmethylhydroxypyridine malate improves the retinal electrophysiological state after 72 h of reperfusion; in the group of rats treated with l-isomer of ethylmethylhydroxypyridine malate, the coefficient b/a was reliably increased by 9.5%, p < 0.05, in comparison with animals treated with Emoxipine, and by 91.7%, p < 0.05, in comparison with the group with no treatment. Furthermore, it prevents the development of ischemic changes in the retina observed in ophthalmoscopy to a greater extent than Emoxipine.

[Complex assessment of retinal ischemic damage in patients with retinal vein occlusion]

PURPOSE

To evaluate the effectiveness of treatment and the possibility of restoring visual functions in patients with retinal vein occlusion (RVO) depending on the initial degree of macular ischemia.

MATERIAL AND METHODS

The study included 84 patients with RVO. The main inclusion criteria were the presence of macular edema in the setting of RVO with the duration of no more than 3 months and without any previous treatment. All patients underwent intravitreal injections of an angiogenesis inhibitor, followed by laser treatment when necessary. A comparative analysis of the results was carried out in groups that were opposite in terms of the clinical effect - before the start of the therapy, after 1 month, and after 12 months. All patients and the control group members underwent standard ophthalmological examination as well as electroretinography, fluorescence angiography, optical coherence tomography (OCT), and OCT angiography.

RESULTS

Based on data obtained during 12 months of the follow-up, the comparative analysis of the initial ophthalmic status of patients with RVO with opposite clinical effect resulted in derivation of 3 clinical groups that correspond to the degrees of macular ischemia - mild, moderate and severe.

CONCLUSION

Determination of the degree of macular ischemia at the stage of primary diagnosis can improve the treatment effectiveness and inform the patients about the sequence and duration of anti-VEGF therapy. Intravitreal injections of ranibizumab in retinal vein occlusion are carried out before the elimination of macular edema and further in the on-demand mode, while the number of injections can vary from one to monthly injections during the year.

A Model for Graded Retinal Ischemia in Rats

Purpose

Retinal ischemic injury depends on grade and duration of an ischemic insult. We developed a method to induce ischemic injury in rats permitting: (1) Variable grades of retinal blood flow (F) reduction, (2) controllable duration of F reduction, (3) injury without collateral neural damage, and (4) optical measurements of F and O₂-related factors: O₂ delivery (DO₂), O₂ extraction fraction (OEF), and metabolic rate of O₂ (MO₂).

Methods

In five anesthetized rats the left common carotid artery (CA) was ligated and the right CA was exposed. A variable clamp having a backstop and a rod mounted on a micromanipulator straddled the right CA. Advancing the rod with the micromanipulator produced graded compressions of the CA. F and O₂-related factors were measured with established optical techniques.

Results

Four to seven grades of F for at least 10 minutes were achieved per rat. F decreased only with compressions of over 60%. DO₂ changed in proportion to F, particularly at low F. As F decreased, OEF initially changed little, but then rose steeply to its maximum of 1 when F was approximately 4 μL/min. MO₂ was stable with reduced F until OEF maximized, after which it decreased progressively.

Conclusions

This model in rats permits acute, graded inner retinal ischemia that is reversible after prescribed durations, does not otherwise injure the eye and allows optical measurement of important physiologic factors during ischemia.

Translational Relevance

This model will allow improved understanding of retinal ischemic injury and enable better management of this common, sight-threatening affliction.

Progesterone treatment shows greater protection in brain vs. retina in a rat model of middle cerebral artery occlusion: Progesterone receptor levels may play an important role

BACKGROUND/OBJECTIVE

To determine whether inflammation increases in retina as it does in brain following middle cerebral artery occlusion (MCAO), and whether the neurosteroid progesterone, shown to have protective effects in both retina and brain after MCAO, reduces inflammation in retina as well as brain.

METHODS

MCAO rats treated systemically with progesterone or vehicle were compared with shams. Protein levels of cytosolic NF-κB, nuclear NF-κB, phosphorylated NF-κB, IL-6, TNF-α, CD11b, progesterone receptor A and B, and pregnane X receptor were assessed in retinas and brains at 24 and 48 h using western blots.

RESULTS

Following MCAO, significant increases were observed in the following inflammatory markers: pNF-κB and CD11b at 24 h in both brain and retina, nuclear NF-κB at 24 h in brain and 48 h in retina, and TNF-α at 24 h in brain.Progesterone treatment in MCAO animals significantly attenuated levels of the following markers in brain: pNF-κB, nuclear NF-κB, IL-6, TNF-α, and CD11b, with significantly increased levels of cytosolic NF-κB. Retinas from progesterone-treated animals showed significantly reduced levels of nuclear NF-κB and IL-6 and increased levels of cytosolic NF-κB, with a trend for reduction in other markers. Post-MCAO, progesterone receptors A and B were upregulated in brain and downregulated in retina.

CONCLUSION

Inflammatory markers increased in both brain and retina after MCAO, with greater increases observed in brain. Progesterone treatment reduced inflammation, with more dramatic reductions observed in brain than retina. This differential effect may be due to differences in the response of progesterone receptors in brain and retina after injury.

Neovascular glaucoma: Handling in the future

Neovascular glaucoma (NVG), which is refractory to both medical management and surgical intervention, is a disastrous ocular disease for it always ends up with intolerable pain and extinguishing patients' residual visual function. Since insufficient acknowledge of the pathophysiological and molecular mechanisms of NVG, it has been laying a challenging dilemma of managing NVG in clinical practice for a long time. Along with the progression on some new agents and surgical options targeting certain possible roles in the NVG process, there seems having been some new sights but still much unknown and to be revealed. This review discusses the underlying etiologic diseases of NVG, molecular findings and characteristics of its pathogenic process, as well as the management of NVG in detail. In addition, here represents some of our hypothesis regarding the interesting findings about NVG in clinical practice, aiming to provide some new enlightenment for future research.

Optic Nerve Degeneration after Retinal Ischemia/Reperfusion in a Rodent Model

Retinal ischemia is a common pathomechanism in many ocular disorders such as age-related macular degeneration (AMD), diabetic retinopathy, glaucoma or retinal vascular occlusion. Several studies demonstrated that ischemia/reperfusion (I/R) leads to morphological and functional changes of different retinal cell types. However, little is known about the ischemic effects on the optic nerve. The goal of this study was to evaluate these effects. Ischemia was induced by raising the intraocular pressure (IOP) in one eye of rats to 140 mmHg for 1 h followed by natural reperfusion. After 21 days, histological as well as quantitative real-time PCR (qRT-PCR) analyses of optic nerves were performed. Ischemic optic nerves showed an infiltration of cells and also degeneration with signs of demyelination. Furthermore, a migration and an activation of microglia could be observed histologically as well as on mRNA level. In regard to macroglia, a trend toward gliosis could be noted after ischemia induction by vimentin staining. Additionally, an up-regulation of glial fibrillary acidic protein (GFAP) mRNA was found in ischemic optic nerves. Counting of oligodendrocyte transcription factor 2 positive (Olig2⁺) cells revealed a decrease of oligodendrocytes in the ischemic group. Also, myelin basic protein (MBP) and myelin oligodendrocyte glycoprotein (MOG) mRNA expression was down-regulated after induction of I/R. On immunohistological level, a decrease of MOG was detectable in ischemic optic nerves as well. In addition, SMI-32 stained neurofilaments of longitudinal optic nerve sections showed a strong structural damage of the ischemic optic nerves in comparison to controls. Consequently, retinal ischemia impacts optic nerve degeneration. These findings could help to better understand the course of destruction in the optic nerve after an ischemic insult. Especially for therapeutic studies, the optic nerve is important because of its susceptibility to be damaged as a result to retinal ischemic injury and also its connecting function between the eye and the brain. So, future drug screenings should target not only the retina, but also the functionality and structure of the optic nerve. In the future, these results could lead to the development of new therapeutic strategies for treatment of ischemic injury.

Protective Effect of Intravitreal Administration of Exosomes Derived from Mesenchymal Stem Cells on Retinal Ischemia

PURPOSE

Exosomes derived from human mesenchymal stem cells (hMSCs) cultured under hypoxic conditions contain proteins and growth factors that promote angiogenesis. This study investigated the effect of intravitreal administration of these exosomes on retinal ischemia using a murine model.

METHODS

Oxygen-induced retinopathy (OIR) was induced by exposing one-week-old male C57BL/6J mice to 5 days of 75% hyperoxic conditioning, and returning to room air. After hyperoxic conditioning, the right eye of each mouse was injected intravitreally with 1 µl saline or exosomes derived from hMSCs and compared to control mice of the same age raised in room air without OIR injected intravitreally with saline. Two weeks post-injection, fluorescein angiography (FA) and phase-variance optical coherence tomography angiography (pvOCTA) were used to assess retinal perfusion. Retinal thickness was determined by OCT. The extent of retinal neovascularization was quantitated histologically by counting vascular nuclei on the retinal surface.

RESULTS

Among eyes with OIR, intravitreal exosome treatment partially preserved retinal vascular flow in vivo and reduced associated retinal thinning; retinal thickness on OCT was 111.1 ± 7.4µm with saline versus 132.1 ± 11.6µm with exosome, p < 0.001. Retinal neovascularization among OIR eyes was reduced with exosome treatment when compared to saline-treated eyes (7.75 ± 3.68 versus 2.68 ± 1.35 neovascular nuclei per section, p < 0.0001). No immunogenicity or ocular/systemic adverse effect was associated with intravitreal exosome treatment.

CONCLUSIONS

Intravitreal administration of exosomes derived from hMSCs was well tolerated without immunosuppression and decreased the severity of retinal ischemia in this murine model. This appealing novel non-cellular therapeutic approach warrants further exploration.

Neovascular glaucoma after vitrectomy in patients with proliferative diabetic retinopathy

To evaluate the prevalence and risk factors of neovascular glaucoma (NVG) after vitrectomy in patients with vitreous hemorrhage associated with proliferative diabetic retinopathy (PDR). This retrospective, noncomparative, observational study included 127 eyes of 127 patients with PDR who received vitrectomy with a follow-up period of at least 6 months. The prevalence of NVG and associated risk factors were assessed including sex, age, previous panretinal photocoagulation, baseline intraocular pressure, combined phacovitrectomy, and pretreatment with intravitreal bevacizumab (IVB) before vitrectomy for the treatment of vitreous hemorrhage. NVG developed in 15 (11.8%) of 127 patients. Of the 15 eyes with NVG, 11 cases (73.3%) postoperatively developed NVG within 6 months. Postoperative NVG was associated with preoperative IVB treatment (odds ratio, 4.43; P = 0.019). The prevalence of NVG after vitrectomy was 11.8%, and an associated risk factor for NVG was preoperative IVB for the treatment of vitreous hemorrhage.