Cost Effectiveness of Treatments for Diabetic Retinopathy: A Systematic Literature Review

Impact of Bariatric Surgery on Treatment Burden and Progression of Diabetic Retinopathy

Purpose: To assess the severity, progression, and treatment burden of diabetic retinopathy (DR) in patients after bariatric surgery compared with controls. Methods: A retrospective cohort study was performed of patients with type 2 diabetes and DR seen at the Duke Eye Center between 2014 and 2023. Clinical data included hemoglobin A1c (HbA1c), diagnostic stage of DR, diabetic macular edema (DME) or vitreous hemorrhage (VH), visual acuity (VA), and treatment burden at baseline and follow-up. Generalized estimating equation analysis was used to account for the correlation between 2 eyes of the same patient. Results: Sixteen patients who had bariatric surgery were matched by age, sex, and duration of diabetes with 60 control patients managed medically during the same time period. The HbA1c level, severity of DR, presence of DME or VH, VA, and treatment burden were not significantly different (all P > .05) at the baseline examination. On average, patients were followed for 6 years. The HbA1c level at the follow-up was significantly lower in the bariatric surgery group (6.4% vs 8.5%; P < .001). At the follow-up, the treatment burden was reduced in the bariatric surgery group compared with the control group (P = .04). There was a clear trend toward reduced progression of DR and treatment burden in the bariatric surgery group over the follow-up. Conclusions: Bariatric surgery may improve glycemic control, stabilize DR progression, and reduce the treatment burden, which may have a significant impact on quality of life for patients with DR.

GRg1 inhibits the TLR4/NF-kB signaling pathway by upregulating miR-216a-5p to reduce growth factors and inflammatory cytokines in DR

BACKGROUND

Diabetic retinopathy (DR) is a common diabetic neurodegenerative disease that affects vision in severe cases. Current therapeutic drugs are ineffective for some patients with severe side effects, and ginsenoside-Rg1 (GRg1) has been shown to protect against DR and may serve as a new potential drug for DR. This study aimed to confirm the protective effect of GRg1 against DR and its molecular mechanism.

METHODS

Human retinal microvascular endothelial cells (hRMECs) and rats were used to construct DR models in vitro and in vivo. Cell proliferation was detected by BrdU assays, the cell cycle was detected by flow cytometry, and TNF-α, IL-6 and IL-1β levels were detected by ELISA. qRT‒PCR, Western blotting and immunohistochemistry were used to detect the expression of related genes and proteins, and angiogenesis assays were used to assess angiogenesis. RIP and RNA pull down assays were used to determine the relationship between miR-216a-5p and TLR4; retinal structure and changes were observed by HE staining and retinal digestive spread assays.

RESULTS

GRg1 effectively inhibited HG-induced hRMEC proliferation, cell cycle progression and angiogenesis and reduced the levels of intracellular inflammatory cytokines and growth factors. HG downregulated the expression of miR-216a-5p and upregulated the expression of TLR4/NF-kB signaling pathway-related proteins. Importantly, GRg1 inhibited TLR4/NF-kB signaling pathway activation by upregulating miR-216a-5p, thereby inhibiting HG-induced cell proliferation, cell cycle progression, angiogenesis, and the production of inflammatory cytokines and growth factors. In addition, animal experiments confirmed the results of the cell experiments.

CONCLUSIONS

GRg1 inhibits TLR4/NF-kB signaling by upregulating miR-216a-5p to reduce growth factors and inflammatory cytokines in DR, providing a potential therapeutic strategy for DR.

A systematic literature review of machine learning based risk prediction models for diabetic retinopathy progression

Diabetic Retinopathy (DR) is the most popular debilitating impairment of diabetes and it progresses symptom-free until a sudden loss of vision occurs. Understanding the progression of DR is a pressing issue in clinical research and practice. In this systematic review of articles on Machine Learning (ML) based risk prediction models for DR progression, ever since the use of Artificial Intelligence (AI) for DR detection, there have been more cross-sectional studies with different algorithms of use of AI, there haven't been many longitudinal studies for the AI based risk prediction models. This paper proposes a novel review to fill in the gaps identified in current reviews and facilitate other researchers with current research solutions for developing AI-based risk prediction models for DR progression and closely related problems; synthesize the current results from these studies and identify research challenges, limitations and gaps to inform the selection of machine learning techniques and predictors to build novel prediction models. Additionally, this paper suggested six (6) deep AI-related technical and critical discussion of the adopted strategies and approaches. The Systematic Literature Review (SLR) methodology was employed to gather relevant studies. We searched IEEE Xplore, PubMed, Springer Link, Google Scholar, and Science Direct electronic databases for papers published from January 2017 to 30th April 2023. Thirteen (13) studies were chosen on the basis of their relevance to the review questions and satisfying the selection criteria. However, findings from the literature review exposed some critical research gaps that need to be addressed in future research to improve on the performance of risk prediction models for DR progression.

Diabetic Macular Oedema Guidelines: An Australian Perspective

The number of people living with diabetes is expected to rise to 578 million by 2030 and to 700 million by 2045, exacting a severe socioeconomic burden on healthcare systems around the globe. This is also reflected in the increasing numbers of people with ocular complications of diabetes (namely, diabetic macular oedema (DMO) and diabetic retinopathy (DR)). In one study examining the global prevalence of DR, 35% of people with diabetes had some form of DR, 7% had PDR, 7% had DMO, and 10% were affected by these vision-threatening stages. In many regions of the world (Australia included), DR is one of the top three leading causes of vision loss amongst working age adults (20-74 years). In the management of DMO, the landmark ETDRS study demonstrated that moderate visual loss, defined as doubling of the visual angle, can be reduced by 50% or more by focal/grid laser photocoagulation. However, over the last 20 years, antivascular endothelial growth factor (VEGF) and corticosteroid therapies have emerged as alternative options for the management of DMO and provided patients with choices that have higher chances of improving vision than laser alone. In Australia, since the 2008 NHMRC guidelines, there have been significant developments in both the treatment options and treatment schedules for DMO. This working group was therefore assembled to review and address the current management options available in Australia.

DNA methylation in diabetic retinopathy: pathogenetic role and potential therapeutic targets

Background

Diabetic retinopathy (DR), a specific neuron-vascular complication of diabetes, is a major cause of vision loss among middle-aged people worldwide, and the number of DR patients will increase with the increasing incidence of diabetes. At present, it is limited in difficult detection in the early stages, limited treatment and unsatisfactory treatment effects in the advanced stages.

Main body

The pathogenesis of DR is complicated and involves epigenetic modifications, oxidative stress, inflammation and neovascularization. These factors influence each other and jointly promote the development of DR. DNA methylation is the most studied epigenetic modification, which has been a key role in the regulation of gene expression and the occurrence and development of DR. Thus, this review investigates the relationship between DNA methylation and other complex pathological processes in the development of DR. From the perspective of DNA methylation, this review provides basic insights into potential biomarkers for diagnosis, preventable risk factors, and novel targets for treatment.

Conclusion

DNA methylation plays an indispensable role in DR and may serve as a prospective biomarker of this blinding disease in its relatively early stages. In combination with inhibitors of DNA methyltransferases can be a potential approach to delay or even prevent patients from getting advanced stages of DR.

Detection of Diabetic Retinopathy Using Extracted 3D Features from OCT Images

Diabetic retinopathy (DR) is a major health problem that can lead to vision loss if not treated early. In this study, a three-step system for DR detection utilizing optical coherence tomography (OCT) is presented. First, the proposed system segments the retinal layers from the input OCT images. Second, 3D features are extracted from each retinal layer that include the first-order reflectivity and the 3D thickness of the individual OCT layers. Finally, backpropagation neural networks are used to classify OCT images. Experimental studies on 188 cases confirm the advantages of the proposed system over related methods, achieving an accuracy of 96.81%, using the leave-one-subject-out (LOSO) cross-validation. These outcomes show the potential of the suggested method for DR detection using OCT images.

Interpretable machine learning-derived nomogram model for early detection of diabetic retinopathy in type 2 diabetes mellitus: a widely targeted metabolomics study

Objective

Early identification of diabetic retinopathy (DR) is key to prioritizing therapy and preventing permanent blindness. This study aims to propose a machine learning model for DR early diagnosis using metabolomics and clinical indicators.

Methods

From 2017 to 2018, 950 participants were enrolled from two affiliated hospitals of Wenzhou Medical University and Anhui Medical University. A total of 69 matched blocks including healthy volunteers, type 2 diabetes, and DR patients were obtained from a propensity score matching-based metabolomics study. UPLC-ESI-MS/MS system was utilized for serum metabolic fingerprint data. CART decision trees (DT) were used to identify the potential biomarkers. Finally, the nomogram model was developed using the multivariable conditional logistic regression models. The calibration curve, Hosmer–Lemeshow test, receiver operating characteristic curve, and decision curve analysis were applied to evaluate the performance of this predictive model.

Results

The mean age of enrolled subjects was 56.7 years with a standard deviation of 9.2, and 61.4% were males. Based on the DT model, 2-pyrrolidone completely separated healthy controls from diabetic patients, and thiamine triphosphate (ThTP) might be a principal metabolite for DR detection. The developed nomogram model (including diabetes duration, systolic blood pressure and ThTP) shows an excellent quality of classification, with AUCs (95% CI) of 0.99 (0.97–1.00) and 0.99 (0.95–1.00) in training and testing sets, respectively. Furthermore, the predictive model also has a reasonable degree of calibration.

Conclusions

The nomogram presents an accurate and favorable prediction for DR detection. Further research with larger study populations is needed to confirm our findings.

Administration of Melatonin in Diabetic Retinopathy Is Effective and Improves the Efficacy of Mesenchymal Stem Cell Treatment

Stem cell transplantation is a promising therapeutic technique for the treatment of a variety of diseases; nevertheless, stem cell therapy may not always work as well as it could. The goal of this study was to test the hypothesis that employing a powerful antioxidant like melatonin improves stem cell transplantation success and potentiates stem cell function in the therapy of diabetic retinopathy. For this purpose, 50 adult male rats were divided into the following: control group: this group received 0.5 ml of 0.1 M of sodium citrate buffer (pH = 4.5) (intraperitoneal (I.P.)). The confirmed diabetic rats were divided into 4 groups: diabetic group: confirmed diabetic rats received no treatments with a regular follow of the blood glucose profile for 8 weeks; melatonin group: confirmed diabetic rats received melatonin (5 mg/kg/day); stem cell group: the confirmed diabetic rats were given intravitreal injection of stem cells (2 μl cell suspension of stem cells (3 × 10⁴ cells/μl)); and melatonin+stem cell group: confirmed diabetic rats received melatonin (5 mg/kg/day), orally once daily for 8 weeks, and 2 μl cell suspension of stem cells (3 × 10⁴ cells/μl) was carefully injected into the vitreous cavity. Our results showed that administration of melatonin and/or stem cell restored the retinal oxidative/antioxidant redox and reduced retinal inflammatory mediators. Coadministration of melatonin and stem cells enhanced the number of transplanted stem cells in the retinal tissue and significantly reduced retinal BDEF, VEGF, APOA1, and RBP4 levels as compared to melatonin and/or stem alone. We may conclude that rats treated with melatonin and stem cells had their retinal oxidative/antioxidant redox values restored to normal and their histological abnormalities reduced. These findings support the hypothesis that interactions with the BDEF, VEGF, APOA1, and RBP4 signaling pathways are responsible for these effects.

Arjunolic acid from Cyclocarya paliurus ameliorates diabetic retinopathy through AMPK/mTOR/HO-1 regulated autophagy pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Cyclocarya paliurus (CP) is a traditional Chinese herb and possesses a variety of biological activities including anti-hyperglycemia, anti-hyperlipidemia, antioxidant and anti-inflammation. Arjunolic acid (AA) is an abundant and bioactive ingredient in CP that shows significant protection against many metabolic diseases such as diabetic complication. Diabetic retinopathy (DR) is a serious complication of diabetes and may lead to vision loss. However, the protective effects and underlying mechanisms of AA against DR is not still understood.

AIM OF THE STUDY

We aimed to investigate whether AA activates AMPK/mTOR/HO-1 regulated autophagy pathway to alleviate DR.

MATERIALS AND METHODS

In the study, the STZ-induced diabetic model of rats was established, and AA with 10 and 30 mg/kg dosages was given orally for ten weeks to investigate their effect on retinal injury of DR. H₂O₂-induced ARPE-19 cells were applied to evaluate anti-apoptosis and anti-oxidant effect of AA.

RESULTS

The results revealed that AA could prevent STZ-induced weight loss and increase the retinal thickness and nuclei counts. The level of HO-1 protein was upregulated both in vivo and in vitro. In addition, AA prevented retinal damage and cell apoptosis through the AMPK-mTOR-regulated autophagy pathway. Furthermore, anti-apoptosis capacity, as well as the expression of HO-1 and LC3 protein, were effectively locked by AMPK inhibitor dorsomorphin dihydrochloride (compound C).

CONCLUSIONS

This finding implies that AA may be a promising candidate drug by protecting retinal cells from STZ-induced oxidative stress and inflammation through the AMPK/mTOR/HO-1 regulated autophagy pathway.

Recent Insights into the Role of Gut Microbiota in Diabetic Retinopathy

The microbiome has become a hot issue in recent years. The composition, modification, alteration, and disturbance of gut microbiota were found to influence important physiological processes, including energy metabolism and microenvironmental homeostasis, and lead to various diseases, including obesity, type 2 diabetes mellitus and chronic kidney disease. Diabetic retinopathy (DR) is a major microvascular complication of diabetes mellitus and one of the leading causes of blindness and vision impairment. The underlying mechanisms in DR pathogenesis remain limited. Recently, important insights have been made regarding possible connections between gut microbiome dysbiosis and ocular disease including DR, uveitis, glaucoma, and age-related macular degeneration, and the concept of a "microbiota-gut-retina axis" has been put forward. Hence, we reviewed current understanding of the relationship between DR and gut microbiota. We summarized potential pathophysiological mechanisms that contribute to the role of the gut microbiota on DR, including hyperglycemia, anti-diabetes drugs, microbial metabolites, and inflammatory properties. We aimed to find novel effective therapeutic options to prevent the onset and development of DR.

Trends in treatment of retinal disorders in the Brazilian Public Health System over a 10-year period

Objective:

To investigate trends in terms of number and cost of intravitreal injection, photocoagulation and panphotocoagulation procedures performed by the Brazilian Public Health System, from 2010 to 2019.

Methods:

The Brazilian Public Health System Database was used as the primary source of data. Intravitreal injection, photocoagulation and panphotocoagulation procedures performed from 2010 to 2019 were investigated. Procedure prevalence and cost trends were analyzed according to year and region. Annual trends were examined using generalized linear models, with a significance level of 5% (p=0.05).

Results:

There was a significant increase in the prevalence of intravitreal injections (1,088%), panphotocoagulation (51%) and photocoagulation (37%) procedures from 2010 to 2019. Intravitreal injections accounted for the most significant increase. However, costs were not significantly readjusted over the years.

Conclusion:

Over a 10-year period, there was a significant increase in the number of procedures associated with retinal disorders. Procedure costs saw little readjustments over time. In spite of limitations, inaccuracies and lack of details, the Brazilian Public Health System Database is the primary source of data for the Public Health System related research in Brazil, and can contribute with information on ocular health and costs of ophthalmic procedures.

Long non-coding RNA MEG3 inhibits neovascularization in diabetic retinopathy by regulating microRNA miR-6720-5p and cytochrome B5 reductase 2

Diabetic retinopathy (DR) is a major cause of vision loss in working and elderly populations. long non-coding RNA (LncRNA) MEG3 is thought to have some effect on DR, but the exact mechanism remains to be clarified. The expression levels of lncRNA MEG3, miR-6720-5p, and cytochrome B5 reductase 2 (CYB5R2) in human retinal microvascular endothelial cells (hRMECs) were detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), transwell migration, and tube formation assays were used to determine the cell viability, migration, and tube formation ability of hRMECs, respectively. The interaction of MEG3, miR-6720-5p, and CYB5R2 was detected and explored by a luciferase assay. The expression of MEG3 and CYB5R2 was upregulated and that of miR-6720-5p was downregulated in patients with DR and hRMECs treated with high glucose. Knocking down MEG3 or CYB5R2 promoted proliferation, migration, and neovascularization in hRMECs. The intervention of miR-6720-5p reversed the effect of MEG3 knockdown on hRMEC function, and this effect was eliminated by silencing CYB5R2. Therefore, MEG3 acted as a sponge to suppress miR-6720-5p and regulate the expression of CYB5R2, thereby inhibiting DR neovascularization.

Cost-effectiveness of dexamethasone and triamcinolone for the treatment of diabetic macular oedema in Finland: A Markov-model

PURPOSE

Diabetic macular oedema (DMO), a complication of diabetes, causes vision loss and blindness. Corticosteroids are usually used as a second-line treatment. The aim of this study was to analyse the cost-effectiveness of dexamethasone implants compared to cheaper and more frequently applied triamcinolone injections.

METHODS

Markov-modelling, which incorporated both eyes, was used for economic evaluation. The model consisted of five health states based on visual acuity, illustrating the progression of DMO. A cycle length of five months was chosen for dexamethasone and four months for triamcinolone. Time horizons of two and five years were applied. Transition probabilities and health state utilities were sourced from previous studies. The perspective used in this analysis was the hospital perspective. The health care costs were acquired from Kuopio University Hospital in Finland.

RESULTS

In this cost-effectiveness analysis, the incremental cost-effectiveness ratio ICER with 3% discount rate was €56 591/QALY for a two-year follow-up and -€1 110 942/QALY for a five-year follow-up. In order to consider dexamethasone as cost-effective over a 2-year time horizon, the WTP needs to be around €55 000/QALY. Over the five-year follow-up, triamcinolone is clearly a dominant treatment. Sensitivity analyses support the cost-effectiveness of dexamethasone over a 2-year time horizon.

CONCLUSIONS

Since the sensitivity analyses support the results, dexamethasone would be a cost-effective treatment during the first two years with WTP threshold around €55 000/QALY, and triamcinolone would be a convenient treatment after that. This recommendation is in line with the guidelines of EURETINA.

Pharmacokinetics and Safety of an Intravitreal Humanized Anti-VEGF-A Monoclonal Antibody (PRO-169), a Biosimilar Candidate to Bevacizumab

Background

PRO-169 is a biosimilar candidate to bevacizumab (BEV), a monoclonal antibody (mAb) that inhibits vascular endothelial growth factor-A (VEGF-A) developed for intravitreal use. The current study demonstrates the intraocular pharmacokinetics (PK) of PRO-169 and its safety using New Zealand white (NZW) rabbits.

Methods

Intraocular concentration was evaluated in thirty-six rabbits at 1h, 1, 2, 5, 14 and 30 days after a single bilateral injection of PRO-169 or BEV (1.25 mg/0.05 mL). In a secondary experiment, safety was evaluated after three consecutive unilateral injections at 30-day intervals in twenty-four rabbits (PRO-169: 1.25 mg/0.05 mL or ranibizumab [RZB]: 0.5 mg/0.05 mL), by liver-associated enzymes (LAE), ophthalmological examination and adverse event (AE) incidence. Primary endpoints were vitreous maximum concentration (C_max), time to attain maximum concentration (t_max), area under curve (AUC_0-t), half-life (t_1/2) and LAE. Secondary endpoints included aqueous humor (AH) and plasma pharmacokinetics, clinical examination and AEs.

Results

The C_max in the vitreous was 593.75 ± 45.63 (PRO-169) vs 644.79 ± 62.65 µg/mL (BEV) (p= 0.136). T_max was 0.53 ± 0.82 vs 0.85 ± 0.73 days (p= 0.330). The AUC_0-t was 3837.72 ± 465.91 vs 4247.31 ± 93.99 days*µg/mL (p= 0.052) and the half-life was 4.99 ± 0.89 vs 5.18 ± 0.88 days (p= 0.711). LAEs were normal in 92% of NZW rabbits; no differences between groups were observed (p>0.05). The AH and plasma PKs were also similar. Finally, clinical examinations found no alterations. AEs were observed in 25% of PRO-169 rabbits, without differences vs RZB (p=0.399).

Conclusion

PRO-169 can be efficiently diffused and distributed in ocular compartments, showing vitreous pharmacokinetics analogous to BEV. The safety experiment did not find evidence of clinical alterations from a repeated injection of PRO-169. These results provide scientific justification supporting that PRO-169 should be evaluated in future clinical trials to confirm its safety and efficacy.

Low circulating dihomo-gamma-linolenic acid is associated with diabetic retinopathy: a cross sectional study of KAMOGAWA-DM cohort study

Diabetic retinopathy (DR), one of the major complications of diabetes, can cause blindness and reduce quality of life. Dyslipidemia is reported to be associated with DR, whereas arachidonic acid may have a protective effect against DR. We aimed to investigate the association of circulating n-3 and n-6 polyunsaturated fatty acids (PUFAs) with DR. In this cross-sectional study, 190 Japanese patients with type 2 diabetes were classified as no diabetic retinopathy (NDR), simple diabetic retinopathy (SDR), or proliferative diabetic retinopathy (PDR) including pre-proliferative diabetic retinopathy. Circulating fatty acids (FAs) were measured by gas chromatograph-mass spectrometry. Logistic regression analysis was performed to investigate the association between the levels of FAs and the presence of DR. The average age, body mass index and the duration of diabetes were 62.7 ± 12.1 years, 25.0 ± 4.5 kg/m², and 9.8 ± 8.7 years, respectively. Twenty-seven patients were diagnosed with DR. Circulating levels of dihomo-gamma-linolenic acid (DGLA) in the NDR (n = 163), SDR (n = 13) and PDR (n = 14) groups were 28.3 ± 11.0 μg/mL, 24.4 ± 9.7 μg/mL, and 21.8 ± 6.2 μg/mL, respectively (p = 0.032). The logarithm of circulating DGLA levels was associated with the presence of DR after adjusting for covariates (OR of 1-unit increment: 0.79, 95% CI: 0.62-1.00, p = 0.049). Circulating DGLA was negatively associated with the presence of DR.

Outcomes of a 2-year treat-and-extend regimen with aflibercept for diabetic macular edema

This prospective, open-label, single-arm, non-randomized clinical trial, assessed the efficacy of a 2-year treat-and-extend (T&E) regimen involving intravitreal aflibercept injection (IAI), with the longest treatment interval set to 16 weeks, and adjunct focal/grid laser in diabetic macula edema (DME) patients. We examined 40 eyes (40 adults) with fovea-involving DME from 8 Japanese centers between April 2015 and February 2017. Participants received IAI with an induction period featuring monthly injections and a subsequent T&E period featuring 8–16-week injection interval, adjusted based on optical coherence tomography findings. The primary endpoints were mean changes in the best-corrected visual acuity (BCVA) and central subfield macular thickness (CST) from baseline. Thirty patients (75%) completed the 2-year follow-up. The mean BCVA and CST changed from 60.5 ± 15.6 letters and 499.2 ± 105.6 µm at baseline to 66.6 ± 17.1 letters (P = 0.217) and 315.2 ± 79.0 µm (P < 0.001), respectively, after 2 years. The treatment interval was extended to 12 and 16 weeks in 6.7% and 66.7% of patients, respectively, at the end of 2 years. The T&E aflibercept regimen with the longest treatment interval set to 16 weeks, with adjunct focal/grid laser may be a rational 2-year treatment strategy for DME.

Changes of visual fields in treatment of proliferative diabetic retinopathy: a systematic review

The aim of this systematic review was to compare certain side-effects [visual fields (VF), dark adaptation, colour vision (CV) and contrast sensitivity (CS)] of conventional panretinal photocoagulation (PRP) with those of other treatments in proliferative diabetic retinopathy (PDR). A systematic literature search was conducted on 30 November 2018 in PubMed and Embase. The search comprised the keywords 'proliferative diabetic retinopathy', 'laser', 'treatment' and 'anti-vegf'. We included prospective studies and randomized controlled trials that investigated certain side-effects (VF, dark adaptation, CV, CS) in treatment of PDR (primary outcome). In total, 1867 articles were screened, and 10 studies were included (2176 eyes of 2086 patients examined in the VF studies and 1360 eyes of 1360 patients examined in the CV and CS studies). Visual fields (VF) were investigated in 10 studies, CV in one study and CS in one study. Treatment modalities included conventional PRP, other modalities of laser treatment and vascular endothelial growth factor (VEGF) inhibitors. Four studies demonstrated a worse VF impact of PRP than VEGF inhibitors. Seven studies reported of an overall worsening in VF after laser with no differences between different laser approaches. No differences were found in CV or CS. Overall, we found a trend, confirmed in four large studies, towards VEGF inhibitors causing less harm to VF compared to conventional PRP. Whilst VF was generally depressed after laser, it did not differ between different treatment approaches. Furthermore, it was not possible to make certain conclusions of CV or CS, with only one study in each field.

Gene Therapy Intervention in Neovascular Eye Disease: A Recent Update

Aberrant growth of blood vessels (neovascularization) is a key feature of severe eye diseases that can cause legal blindness, including neovascular age-related macular degeneration (nAMD) and diabetic retinopathy (DR). The development of anti-vascular endothelial growth factor (VEGF) agents has revolutionized the treatment of ocular neovascularization. Novel proangiogenic targets, such as angiopoietin and platelet-derived growth factor (PDGF), are under development for patients who respond poorly to anti-VEGF therapy and to reduce adverse effects from long-term VEGF inhibition. A rapidly advancing area is gene therapy, which may provide significant therapeutic benefits. Viral vector-mediated transgene delivery provides the potential for continuous production of antiangiogenic proteins, which would avoid the need for repeated anti-VEGF injections. Gene silencing with RNA interference to target ocular angiogenesis has been investigated in clinical trials. Proof-of-concept gene therapy studies using gene-editing tools such as CRISPR-Cas have already been shown to be effective in suppressing neovascularization in animal models, highlighting the therapeutic potential of the system for treatment of aberrant ocular angiogenesis. This review provides updates on the development of anti-VEGF agents and novel antiangiogenic targets. We also summarize current gene therapy strategies already in clinical trials and those with the latest approaches utilizing CRISPR-Cas gene editing against aberrant ocular neovascularization.

Combination Antivascular Endothelial Growth Factor and Modified Panretinal Photocoagulation in Management of Proliferative Diabetic Retinopathy

Purpose:

This work evaluates the effects of combined intravitreal antivascular endothelial growth factor (anti-VEGF) and modified panretinal photocoagulation (PRP) for management of proliferative diabetic retinopathy (PDR).

Methods:

This retrospective case series included 37 eyes of 33 patients with high-risk PDR. Anti-VEGF injections (≥ 2) were followed by modified, midperipheral PRP performed in 2 or more sessions. Visual and anatomic outcomes were tracked for 1 year after treatment. Regression analysis was performed for factors predictive of final outcomes.

Results:

Mean visual acuity (VA) at initial and final visit were 20/50 and 20/40 ( P = .22), respectively, over a mean follow-up duration of 341.4 days. Central foveal thickness decreased from 321.8 µm to 258.6 µm ( P = .01). Resolution of PDR was achieved in 94.6% of eyes, with 5.4% of eyes requiring additional anti-VEGF for persistent neovascularization. Final VA was significantly associated with baseline VA, VA at 1 month, and any adverse anatomical events. Treatment noncompliance was present in 24.3%; compliance decreased with increasing medical comorbidities, but was not significantly associated with final VA.

Conclusions:

Combination of anti-VEGF and modified PRP preserved VA and yielded PDR regression in the majority of eyes. This combination provides rapid PDR regression with anti-VEGF while achieving durable disease suppression in this real-world cohort without traditional PRP.

Safety of Intravitreal Injection of Stivant, a Biosimilar to Bevacizumab, in Rabbit Eyes

Purpose

To evaluate the safety of intravitreal injection of Stivant, a biosimilar to bevacizumab, in rabbits using electrophysiological and histological analysis.

Methods

Both eyes of 41 New Zealand albino rabbits were injected with 0.1 mL (2.5 mg) of Stivant. The rabbits were scheduled to be sacrificed 1, 2, 7, 14, and 28 days after injection for histopathological evaluations. Clinical examinations and electroretinography (ERG) were performed at baseline and just before sacrificing the rabbits. Fourteen separate rabbits received a reference drug (Avastin) and were considered as the control group. Furthermore, three other rabbits received the same volume of saline (saline control group). Rabbits of both control groups were sacrificed four weeks after injection. ERG was performed 1, 2, 7, 14, and 28 days after injections.

Results

No significant difference was observed in a- and b-wave amplitudes and latency after intravitreal Stivant injection between baseline and different time points. Moreover, there was no statistically significant difference in wave amplitudes and latency between the Stivant and control groups. The histology of rabbit eyes of the Stivant and control groups after intravitreal injections was not distinguishable.

Conclusion

The biosimilar Stivant, up to a dose of 2.5 mg, did not appear to be toxic to the retina in albino rabbits. These results suggest that this drug could be a safe and inexpensive alternative to intravitreal bevacizumab. The efficacy of these injections was not investigated in this study and needs to be evaluated in future studies.

Safety of Intravitreal Injection of Biosimilar of Aflibercept in Rabbit Eyes

Purpose

To assess the safety of biosimilar intravitreal aflibercept (CinnaGen Co., Iran) compared to the reference product (Eylea®; Bayer Schweiz AG, Zurich, Switzerland) in rabbit eyes through functional and histologic studies.

Methods

Forty New Zealand albino rabbits were recruited to the study and were divided into four groups to be sacrificed at 48 hours, one, two, and four weeks after injections. In each group, five rabbits received 0.05 mL (2 mg) biosimilar aflibercept in the right eye and 0.05 mL saline in the left eye as the control, and in a similar manner, the remaining five rabbits received the reference drug in the right eye and saline in the left eye. All the rabbits underwent comprehensive ophthalmic examination and electroretinography (ERG) tests at baseline and also just before enucleation at the specific predefined time points. The enucleated eyes were prepared for retinal toxicity histological examination.

Results

No retinal toxicity was observed based on histologic and ERG findings in all groups. Choroidal congestion was revealed after 1 week in an eye that was injected with biosimilar aflibercept, although the similar finding was detected in the contralateral eye which received saline. Also, one subject which received the reference drug showed chronic vitritis and lymphoplasmocytic reaction of the optic disc at week 4. The remaining subjects showed no histologic changes.

Conclusion

The 2 mg intravitreal injection of biosimilar aflibercept (CinnaGen Co., Iran) was found to be nontoxic in rabbit eyes in the short-term period. Further studies are required to warrant the efficacy and safety profile of the drug in human subjects.

Melatonin inhibits Müller cell activation and pro-inflammatory cytokine production via upregulating the MEG3/miR-204/Sirt1 axis in experimental diabetic retinopathy

Diabetic retinopathy (DR) is the most common ocular complication caused by diabetes mellitus and is the main cause of visual impairment in working-age people. Reactive gliosis and pro-inflammatory cytokine production by Müller cells contribute to the progression of DR. Melatonin is a strong anti-inflammatory hormone, mediating the cytoprotective effect of a variety of retinal cells against hyperglycemia. In this study, melatonin inhibited the gliosis activation and inflammatory cytokine production of Müller cells in both in vitro and in vivo models of DR. The melatonin membrane blocker, Luzindole, invalidated the melatonin-mediated protective effect on Müller cells. Furthermore, melatonin inhibited Müller cell activation and pro-inflammatory cytokine production by upregulating the long noncoding RNA maternally expressed gene 3/miR-204/sirtuin 1 axis. In conclusion, our study suggested that melatonin treatment could be a novel therapeutic strategy for DR.

Adjuvant Therapies in Diabetic Retinopathy as an Early Approach to Delay Its Progression: The Importance of Oxidative Stress and Inflammation

Diabetes mellitus (DM) is a progressive disease induced by a sustained state of chronic hyperglycemia that can lead to several complications targeting highly metabolic cells. Diabetic retinopathy (DR) is a multifactorial microvascular complication of DM, with high prevalence, which can ultimately lead to visual impairment. The genesis of DR involves a complex variety of pathways such as oxidative stress, inflammation, apoptosis, neurodegeneration, angiogenesis, lipid peroxidation, and endoplasmic reticulum (ER) stress, each possessing potential therapeutic biomarkers. A specific treatment has yet to be developed for early stages of DR since no management is given other than glycemic control until the proliferative stage develops, offering a poor visual prognosis to the patient. In this narrative review article, we evaluate different dietary regimens, such as the Mediterranean diet, Dietary Pattern to Stop Hypertension (DASH) and their functional foods, and low-calorie diets (LCDs). Nutraceuticals have also been assessed in DR on account of their antioxidant, anti-inflammatory, and antiangiogenic properties, which may have an important impact on the physiopathology of DR. These nutraceuticals have shown to lower reactive oxygen species (ROS), important inflammatory factors, cytokines, and endothelial damage biomarkers either as monotherapies or combined therapies or concomitantly with established diabetes management or nonconventional adjuvant drugs like topical nonsteroidal anti-inflammatory drugs (NSAIDs).

Melatonin: new insights on its therapeutic properties in diabetic complications

Diabetes and diabetic complications are considered as leading causes of both morbidity and mortality in the world. Unfortunately, routine medical treatments used for affected patients possess undesirable side effects, including kidney and liver damages as well as gastrointestinal adverse reactions. Therefore, exploring the novel therapeutic strategies for diabetic patients is a crucial issue. It has been recently shown that melatonin, as main product of the pineal gland, despite its various pharmacological features including anticancer, anti-aging, antioxidant and anti-inflammatory effects, exerts anti-diabetic properties through regulating various cellular mechanisms. The aim of the present review is to describe potential roles of melatonin in the treatment of diabetes and its complications.

Pterostilbene Prevents Early Diabetic Retinopathy Alterations in a Rabbit Experimental Model

Oxidative stress generated by diabetes plays a key role in the development of diabetic retinopathy (DR), a common diabetic complication. DR remains asymptomatic until it reaches advanced stages, which complicate its treatment. Although it is known that good metabolic control is essential for preventing DR, knowledge of the disease is incomplete and an effective treatment with no side effects is lacking. Pterostilbene (Pter), a natural stilbene with good antioxidant activity, has proved to beneficially affect different pathologies, including diabetes. Therefore, our study aimed to analyse the protective and/or therapeutic capacity of Pter against oxidant damage by characterising early retinal alterations induced by hyperglycaemia, and its possible mechanism of action in a rabbit model of type 1 diabetes mellitus. Pter reduced lipid and protein oxidative damage, and recovered redox status and the main activities of antioxidant enzymes. Moreover, the redox regulation by Pter was associated with activation of the PI3K/AKT/GSK3β/NRF2 pathway. Our results show that Pter is a powerful protective agent that may delay early DR development.

Oxidative Stress and Microvascular Alterations in Diabetic Retinopathy: Future Therapies

Diabetes is a disease that can be treated with oral antidiabetic agents and/or insulin. However, patients' metabolic control is inadequate in a high percentage of them and a major cause of chronic diseases like diabetic retinopathy. Approximately 15% of patients have some degree of diabetic retinopathy when diabetes is first diagnosed, and most will have developed this microvascular complication after 20 years. Early diagnosis of the disease is the best tool to prevent or delay vision loss and reduce the involved costs. However, diabetic retinopathy is an asymptomatic disease and its development to advanced stages reduces the effectiveness of treatments. Today, the recommended treatment for severe nonproliferative and proliferative diabetic retinopathy is photocoagulation with an argon laser and intravitreal injections of anti-VEGF associated with, or not, focal laser for diabetic macular oedema. The use of these therapeutic approaches is severely limited, such as uncomfortable administration for patients, long-term side effects, the costs they incur, and the therapeutic effectiveness of the employed management protocols. Hence, diabetic retinopathy is the widespread diabetic eye disease and a leading cause of blindness in adults in developed countries. The growing interest in using polyphenols, e.g., resveratrol, in treatments related to oxidative stress diseases has spread to diabetic retinopathy. This review focuses on analysing the sources and effects of oxidative stress and inflammation on vascular alterations and diabetic retinopathy development. Furthermore, current and antioxidant therapies, together with new molecular targets, are postulated for diabetic retinopathy treatment.