Intravitreal Steroids for Macular Edema: The Past, the Present, and the Future

Improved triamcinolone acetonide-eluting contact lenses based on cyclodextrins and high hydrostatic pressure assisted complexation

Contact lenses (CLs) constitute an advantageous platform for the topical release of corticosteroids due to their prolonged contact with the eye. However, the lipophilic nature of corticosteroids hampers CLs' ability to release therapeutic amounts. Two approaches to improve loading and release of triamcinolone acetonide (TA) from poly(2-hydroxyethyl methacrylate)-based hydrogels were investigated: adding 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) to the monomers solution before polymerization (HEMA/i-CD) and an hydrogels' post-treatment with HP-β-CD (HEMA/p-CD). The effect of HP-β-CD and sterilization by high hydrostatic pressure (HHP) on the hydrogel properties (water content, oxygen and ion permeability, roughness, transmittance, and stiffness) was evaluated. The HEMA/i-CD hydrogels had stronger affinity for TA, sustaining its release for one day. HHP sterilization promoted the formation of cyclodextrin-TA complexes within the hydrogels, improving their drug-loading capacity »60 %. Cytotoxicity and irritability tests confirmed the safety of the therapeutic CLs. TA released from the hydrogels permeated through ocular tissues ex vivo and showed anti-inflammatory activity. Finally, a previously validated mathematical model was used to estimate the ability of the TA-loaded CLs to deliver therapeutic drug concentrations to the posterior part of the eye. Overall, HP-β-CD-containing CLs are promising candidates for the topical ocular application of TA as an alternative delivery system to intraocular injections.

Glucocorticoid-Induced Ocular Hypertension and Glaucoma

Glucocorticoid (GC) therapy is indicated in many diseases, including ocular diseases. An important side-effect of GC therapy is GC-induced ocular hypertension (GIOHT), which may cause irreversible blindness known as GC-induced glaucoma (GIG). Here, we reviewed the pathological changes that contribute to GIOHT including in the trabecular meshwork and Schlemm's canal at cellular and molecular levels. We also discussed the clinical aspects of GIOHT/GIG including disease prevalence, risk factors, the type of GCs, the route of GC administration, and management strategies.

Intravitreal Triamcinolone Acetonide for Diabetic Macular Edema and Macular Edema Secondary to Retinal Vein Occlusion: A Meta-Analysis

BACKGROUND

The comparative safety and efficacy of different doses of intravitreal triamcinolone acetonide (IVTA) for diabetic macular edema (DME) and macular edema (ME) secondary to retinal vein occlusion (RVO) is unclear.

OBJECTIVES

This meta-analysis aimed to compare the safety and efficacy of different doses of IVTA in this setting.

METHODS

A systematic literature search for randomized clinical trials (RCTs) was conducted on Cochrane Library, Ovid MEDLINE, and EMBASE from January 2005 to May 2022. Studies that reported on patients with DME or ME secondary to RVO that received treatment with different doses of IVTA were included. A random-effects meta-analysis was performed. Cochrane's Risk of Bias Tool 2 was used to assess the risk of bias, and Grading of Recommendations, Assessment, Development and Evaluation (GRADE) guidelines were used to assess certainty of evidence.

RESULTS

Five RCTs reporting on 1,041 eyes at baseline were included in this meta-analysis. In eyes with ME secondary to RVO, high-dose (4 mg) IVTA achieved a significantly better change in best-corrected visual acuity (WMD = -4.75 ETDRS letters, 95% CI = [-7.73, -1.78], p = 0.002) and reduction in retinal thickness (WMD = -93.02 μm, 95% CI = [-153.23, -32.82], p = 0.002) at months 4-6 compared to low-dose (1-2 mg) IVTA. However, high-dose IVTA had a higher risk of intraocular pressure-related adverse events (RR = 2.99, 95% CI = [1.05, 8.50], p = 0.04) and cataract surgery (RR = 5.67, 95% CI = [3.09, 10.41], p < 0.00001) than low-dose IVTA in eyes with ME secondary to RVO. These efficacy and safety differences in high-dose and low-dose IVTA were not observed in DME eyes.

CONCLUSIONS

The RCT evidence in this setting is limited. High-dose IVTA achieved greater improvements in visual acuity and reductions in retinal thickness than low-dose IVTA at months 4-6. However, high-dose IVTA had a less favorable safety profile than low-dose IVTA. The significance of these outcomes was based on patients with ME secondary to RVO, but not DME.

Inflammation: The Link between Neural and Vascular Impairment in the Diabetic Retina and Therapeutic Implications

The etiology of diabetic retinopathy (DR) is complex, multifactorial and compromises all the elements of the retinal neurovascular unit (NVU). This diabetic complication has a chronic low-grade inflammatory component involving multiple inflammatory mediators and adhesion molecules. The diabetic milieu promotes reactive gliosis, pro-inflammatory cytokine production and leukocyte recruitment, which contribute to the disruption of the blood retinal barrier. The understanding and the continuous research of the mechanisms behind the strong inflammatory component of the disease allows the design of new therapeutic strategies to address this unmet medical need. In this context, the aim of this review article is to recapitulate the latest research on the role of inflammation in DR and to discuss the efficacy of currently administered anti-inflammatory treatments and those still under development.

A Comparison of Ocular Complications after 0.7 mg Dexamethasone Implant versus 2 mg of Intravitreal Triamcinolone in Vitrectomized Eyes

OBJECTIVE

To compare the rates of complications in eyes that received a dexamethasone (DEX) implant (0.7 mg) or intravitreal triamcinolone (IVT) (2 mg) to treat postvitrectomy macular edema (ME).

DESIGN

Retrospective, comparative, case series.

SUBJECTS

A total of 148 eyes (147 patients); 75 eyes (75 patients) in the DEX group and 73 eyes (72 patients) in the IVT group.

METHODS

The medical records of patients who received an intravitreal DEX 0.7 mg (Ozurdex) or triamcinolone (2 mg) (Triesence) for postvitrectomy ME between July 2014 and December 2021 with a minimum follow-up of 3 months were reviewed. Ocular hypotony and ocular hypertension were defined as intraocular pressure of < 6 mmHg and > 24 mmHg, respectively.

MAIN OUTCOME MEASURES

The rates of complications.

RESULTS

The follow-up duration was 2.5 ± 1.6 years, with no significant difference between the groups (P = 0.398). The rate of transient ocular hypotony per eye and per injection was significantly higher in the DEX group (10 eyes [13%], 30 of 443 injections [7%]) compared with the IVT group (2 eyes [3%], 2 of 262 injections [0.8%]) (P = 0.039 and < 0.001, respectively). Mean visual acuity significantly decreased at the time of ocular hypotony (P = 0.031), but returned to preinjection level after resolution of the hypotony after a median of 12 days. The incidence of ocular hypertension was higher in the DEX group (23 eyes [31%]) than the IVT group (16 eyes [22%]), but this was not statistically significant (P = 0.307). Ocular hypertension was controlled with observation or topical medication. There were no between-group differences in the incidence of vitreous hemorrhage (DEX, 3 eyes [4%]; IVT, 1 eye [1%]; P = 0.632) or rhegmatogenous retinal detachment (DEX, 3 eyes [4%]; IVT, 0 eyes [0%]; P = 0.253). Four eyes (5%) experienced migration of the DEX implant into the anterior chamber. No eye developed endophthalmitis.

CONCLUSION

The incidence of ocular hypotony, which causes transient visual impairment, was significantly higher in vitrectomized eyes treated with DEX compared with eyes treated with IVT. Injections other than the inferotemporal quadrant or rotating injection sites may be recommended.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Temporal fluctuations of cardiovascular parameters after intravitreal injections

BACKGROUND

Despite the effectiveness of intravitreal injection (IVI) of anti-vascular endothelial growth factor in treating retinal diseases, there remains a paucity of evidence on potential systemic risks associated with this procedure. This study aims to investigate cardiovascular parameters and the risk of hypertensive urgency after IVIs.

METHODS

Patients who received IVIs for retinal/macular diseases were enrolled retrospectively. Patients who received cataract surgeries were enrolled as controls. Systolic and diastolic blood pressure (BP) and heart rate were measured 10 minutes before, immediately after, and more than 30 minutes after IVIs and cataract surgery. Multivariate analysis was performed to evaluate risk factors for hypertensive urgency.

RESULTS

Seventy patients who received IVIs and 95 patients who received cataract surgeries were enrolled. A higher preoperative systolic BP was found in the IVI groups than in the control group (147.0 ± 22.9 vs 136.3 ± 21.8 mmHg, respectively). The patients who received IVIs had a higher increase in perioperative systolic BP immediately after the procedure than the controls (17.43 ± 20.53 mmHg vs 9.11 ± 18.92 mmHg, p = 0.009). The IVI procedure (odds ratio [OR] 4.84, p = 0.008), preoperative systolic BP ≥160 mmHg (OR 17.891, p = 0.001, compared to preoperative systolic BP <140 mmHg), and underlying hypertension (OR 3.305, p = 0.041) were risk factors for hypertensive urgency immediately after the IVIs.

CONCLUSION

We found a transient increase in BP after IVIs, which may have been associated with hypertensive urgency and related cardiovascular disorders in older patients and in those with relevant comorbidities. Clinicians should pay more attention to these patients before performing IVIs.

Steroid Treatment in Macular Edema: A Bibliometric Study and Visualization Analysis

The use of steroids to treat macular edema (ME) is a research hotspot in ophthalmology. We utilized CiteSpace and VOSviewer software to evaluate the Web of Science Core Collection publications and to build visualizing maps to describe the research progress in this topic. There were 3,252 publications for three decades during 1988–2021. The number of studies was low during the first 14 years but has risen consistently in the following two decades. The average publications per year were only 4.8 during 1988–2002, which jumped to 113 per year during 2003–2012, and 227 per year during 2013–2021. These publications came from 83 countries/regions, with the United States, Germany, and Italy leading positions. Most studies were published in Investigative Ophthalmology Visual Science, and Ophthalmology was the most cited journal. We found 9,993 authors, with Bandello F having the most publications and Jonas JB being the most frequently co-cited. According to our research, the most popular keyword is triamcinolone acetonide (TA). Macular edema, diabetic macular edema (DME), retinal vein occlusion (RVO), dexamethasone (DEX), fluocinolone acetonide (FA), and some other keywords were commonly studied in this field. In conclusion, the bibliometric analysis provides a comprehensive overview of steroid hotspots and developmental tendencies in the macular edema study. While anti-VEGF therapy is the first-line treatment for DME and RVO-induced macular edema, steroids implant is a valid option for these DME patients not responding to anti-VEGF therapy and non-DME patients with macular edema. Combined therapy with anti-VEGF and steroid agents is vital for future research.

[Preconditioning of vascularized high-risk eyes using fine-needle diathermy and cross-linking]

BACKGROUND

The risk of allograft rejection following high-risk keratoplasty increases with the area of corneal neovascularization. Pharmaceutical and physical regression of corneal neovascularization before keratoplasty may offer the potential to reduce the risk of graft rejection after high-risk keratoplasty.

OBJECTIVE

This article provides a review of the literature on the preconditioning of vascularized high-risk eyes using fine-needle diathermy and corneal cross-linking (preoperative preconditioning by lymphangioregression).

METHODS

A literature search was carried out in PubMed and a summary of own data is presented.

RESULTS

Animal experimental studies showed that both fine-needle diathermy and corneal cross-linking lead to a regression of corneal neovascularization and prolong graft survival after high-risk keratoplasty. Furthermore, studies from our institute provide first evidence that both procedures also lead to a reduction of corneal neovascularization in the clinical practice and thus potentially reduce the risk of allograft rejection after subsequent high-risk keratoplasty.

DISCUSSION

Fine-needle diathermy and corneal cross-linking provide effective therapeutic approaches for angioregressive treatment and seem to prolong graft survival following high-risk keratoplasty. Larger prospective and controlled clinical trials are needed to further investigate these promising therapeutic approaches.

Outcome of Single Dexamethasone Implant Injection in the Treatment of Persistent Diabetic Macular Edema After Anti-VEGF Treatment: Real-Life Data from a Tertiary Hospital in Jordan

Purpose

To analyze the real-life clinical outcome of a single dexamethasone implant (DEX) injection in the treatment of persistent diabetic macular edema (DME) after anti-vascular endothelial growth factor (anti-VEGF) agents in a sample of the Jordanian population.

Methods

An observational case study design that involved a retrospective chart review analysis in a tertiary hospital in Amman, Jordan. Patients who showed persistent DME after receiving at least six doses of anti-VEGF agents for DME treatment were included.

Results

The study population consisted of 72 participants (29 females, 43 males) having an average age of 66 years. All patients had best-corrected visual acuity (BCVA) less than 0.7 (6/9) and SD-OCT documented center-involved DME. The study results showed that the average baseline BCVA improved from 0.205±0.1 before DEX injection to 0.358±0.1 at 3 months post-injection (p<0.0001). The central mean thickness (CMT) showed significant improvement also (539.347±132.402 to 379.041±99.430, p<0.0001). There was a mean of 3 mmHg increase in intraocular pressure at 3 months post-injection (p<0.0001), however, only 4% of patients required medical treatment. Other inflammatory biomarkers in OCT, such as intraretinal hyper-reflective dots (HRD), showed significant improvement also (23.67±16 to 14.83±13, p<0.0001). No other significant safety concerns were noticed.

Conclusion

A single DEX injection showed significant clinical and anatomical improvement in DME cases that are persistent after anti-VEGF treatment in our sample, with an excellent safety profile. In case of supply shortage of intravitreal injections, which occurs frequently at our center, a single DEX injection may be utilized as an effective DME therapy. Further research is mandated to identify clinical response in a larger sample and more frequent injections.

Efficacy of systemic administration of riboflavin on a rabbit model of corneal alkali burn

Changes in the barrier mechanisms in the eye should determine the rational route for the administration and dosage of each drug in the treatment of traumatic injuries and other pathologies. The aim of this study was to examine the efficacy of intra-arterial delivery of 14C-riboflavin (as an "indicator") and compare it with intravenous and intramuscular administration in an animal model of chemical eye burn. 14C-riboflavin (14C-I) was administered by intra-arterial (carotid artery), intravenous (femoral vein) and intramuscular (femoral muscle) routes. The total radioactivity was determined over 2 h in the plasma and structures of the rabbit's eyes using a scintillation counter. The results of the study show that intravascular administration of 14C-I gives significantly higher concentrations of total radioactivity in the blood and is accompanied by a significant increase in the permeability of the blood-barrier and barrier in eyes suffering from burns. The highest concentration in the plasma and aqueous humour of the anterior chamber of the eye was observed during the first hour with the intra-arterial route of administration of 14C-I in either burnt and unburnt eyes. The distribution of total radioactivity in the structures of the eye over the 2 h of the experiment showed a higher level of the drug under intra-arterial administered in the uveal regions, namely: the iris, ciliary body, choroid, retina and also the sclera and cornea. This experimental model shows that intra-arterial administration can increase the bioavailability of a drug to the structures of the eye within a short period of time.

Corticosteroids in ophthalmology: drug delivery innovations, pharmacology, clinical applications, and future perspectives

Corticosteroids remain the mainstay of the treatment for various ocular conditions affecting the ocular surface, anterior and posterior segments of the eye due to their anti-inflammatory, anti-oedematous, and anti-neovascularization properties. Prednisolone, prednisolone acetate, dexamethasone, triamcinolone acetonide, fluocinolone acetonide, and loteprednol etabonate are amongst the most widely used ophthalmic corticosteroids. Corticosteroids differ in their activity and potency in the eye due to their inherent pharmacological and pharmaceutical differences. Different routes and regimens are available for ocular administration of corticosteroids. Conventional topical application to the eye is the route of choice when targeting diseases affecting the ocular surface and anterior segment, while periocular, intravitreal, and suprachoroidal injections can be potentially effective for posterior segment diseases. Corticosteroid-induced intraocular pressure elevation and cataract formation remain the most significant local risks following topical as well as systemic corticosteroid administration. Invasive drug administration via intracameral, subconjunctival, and intravitreal injection can enhance ocular bioavailability and minimize dose and dosing frequency of administration, yet may exacerbate ocular side effects of corticosteroids. This review provides a critical appraisal of the ophthalmic uses of corticosteroid, routes of administration, drug delivery fundamentals and novel ocular implantable steroid delivery systems, factors influencing side effects, and future perspectives for ocular corticosteroid therapy.

Recent advances in the management of non-infectious posterior uveitis

PURPOSE

To review the current regimens and novel therapeutic modalities in various stages of research and development for the management of non-infectious posterior uveitis (NIPU).

METHODS

We performed a thorough review of current literature using PubMed, Google Scholar and Clinicaltrials.gov to identify the published literature about the available therapeutics and novel drugs/therapies in different stages of clinical trials.

RESULTS

The current management regimen for non-infectious posterior uveitis includes corticosteroids, immunomodulatory therapies and anti-metabolites. However, NIPU requires long-term management for efficacious remission of the disease and to prevent disease relapse. Long-term safety issues associated with steroids have led to efforts to develop novel therapeutic agents including biological response modulators and immunosuppressants. The current therapeutic agents in various stages of development include calcineurin inhibitors, biologic response modifiers and a more a comprehensive modalities like ocular gene therapy as well as novel drug delivery mechanisms for higher bioavailability to the target tissues, with minimal systemic effects.

CONCLUSION

Novel efficacious therapeutic modalities under development will help overcome the challenges associated with the traditional therapeutic agents.

Steroid-induced glaucoma: Epidemiology, pathophysiology, and clinical management

Glucocorticoids are a class of anti-inflammatory drugs commonly used to treat various ocular and systemic conditions. Although the role of glucocorticoids in the treatment of numerous serious inflammatory diseases is pivotal, their prolonged use may increase intraocular pressure resulting in steroid-induced glaucoma. We provide a detailed update on steroid-induced glaucoma as a preventable cause of blindness in the adult and pediatric population and describe its epidemiology, social impact, and risk factors. Furthermore, we explore the propensity of different steroids to increase the intraocular pressure, the role of different routes of steroid administration, dosage and duration of treatment, as well as the clinical features, genetics, and management of steroid-induced glaucoma.

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.

Emerging therapies in the management of macular edema: a review

Macular edema (ME) is a major complication of several vascular and inflammatory retinal diseases. Multiple mechanisms are implicated in its development and lead to visual impairment that could be reversible (the acute stages) or not reversible (long-standing ME). For this reason, an effective approach to the treatment of ME is of paramount importance in order to prevent irreversible damage of visual function. In this review, we discuss the management of ME and, in particular, current data of studies and clinical trials about drugs that have already been evaluated or are under investigation in the management of ME. Although several diseases could lead to the development of ME, we focus on the three main causes: diabetic retinopathy (DR), retinal vein occlusion (RVO), and uveitis. The introduction into clinical practice of anti-vascular endothelial growth factor injections (ranibizumab and aflibercept) and dexamethasone implants has revolutionized the treatment of ME secondary to DR and RVO. However, new drugs are needed in the treatment of resistant forms of ME secondary to DR and RVO. A fluocinolone acetonide implant has been approved by the US Food and Drug Administration for the treatment of diabetic ME but not for RVO. Furthermore, brolucizumab and abicipar pegol have been shown to be effective in preliminary studies and have the chance to be approved soon for diabetic ME treatment. In ME secondary to uveitis, a crucial role is played by corticosteroids and non-biologic immunomodulatory drugs. However, several new biologic agents are under investigation in different clinical trials and could be important new therapeutic options in cases with a low response to first-line therapy. However, only a few of these drugs will enter the market after proving their safety and efficacy. Only after that will we be able to offer a new therapeutic option to patients affected by uveitic ME.

Multimodal Retinal Imaging Findings in Williams-Beuren Syndrome

A 17-year-old male patient diagnosed with Williams-Beuren syndrome presented with a gradual decline in vision in both eyes during a 3-year period. The ophthalmologic examination was notable for numerous loop-shaped tortuous vessels accompanying normal appearing retinal vessels and cystoid macular edema (CME). Mild foveal hypoplasia with a persistence of inner retinal layers was noted on spectral-domain optical coherence tomography (OCT). OCT angiography showed that the abnormal vessels were not retinal vessels but were compatible with prepapillary vascular loops. The CME persisted despite repeated intravitreal bevacizumab treatment. The resolution was observed following an intravitreal triamcinolone acetonide injection. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:514-518.].

Do systemic steroids increase the risk of ocular complication in uveitis patients? Focus on a Italian referral center

INTRODUCTION

To describe the ocular inflammatory and iatrogenic complications in a cohort of uveitic patients treated in an Italian referral centre.

MATERIAL AND METHODS

Retrospective non-comparative case series. Medical history and clinical findings of all consecutive patients referred to the uveitis center of Pisa University from January 2015 to January 2017 were reviewed. Only patients with at least three follow-up visits in our center were included in our series.

RESULTS

Three hundred and eighty-nine patients were visited in our center during study period; only 142 patients (90 men and 52 female) satisfied the inclusion criteria. Mean age at presentation was 41 ± 14 years. The most common ocular feature was anterior uveitis (46%) and was mainly unilateral. A specific etiological diagnosis was established in 61% of patients. At presentation, 71.43% of patients were on medical therapy for rheumatic disease; 42.86% of patients used systemic steroids Cataract and ocular hypertension were the most common ocular complications during the study period but were not statistically related to systemic steroid treatment.

CONCLUSIONS

Systemic steroids treatment in uveitis patients does not seem to increase the risk of iatrogenic complications such as cataract and glaucoma. In our series, increasing age appears to be the main risk factor for cataract and glaucoma development. Key points • Cataract, ocular hypertension, and glaucoma are the most common iatrogenic complications. • Systemic steroids can be safely used in uveitis patients.

The role of inflammation in diabetic eye disease

Mounting evidence suggests that immunological mechanisms play a fundamental role in the pathogenesis of diabetic retinopathy (DR) and diabetic macular edema (DME). Upregulation of cytokines and other proinflammatory mediators leading to persistent low-grade inflammation is believed to actively contribute to the DR-associated damage to the retinal vasculature, inducing breakdown of the blood-retinal barrier, subsequent macular edema formation, and promotion of retinal neovascularization. This review summarizes the current knowledge of the biological processes providing an inflammatory basis for DR and DME. In addition, emerging therapeutic approaches targeting inflammation are discussed, including blockade of angiopoietin 2 and other molecular targets such as interleukin (IL)-6, IL-1β, plasma kallikrein, and integrins.

Humanin Nanoparticles for Reducing Pathological Factors Characteristic of Age-Related Macular Degeneration

BACKGROUND

Humanin is a novel neuronal peptide that has displayed potential in the treatment of Alzheimer's Disease through the suppression of inflammatory IL-6 cytokine receptors. Such receptors are found throughout the body, including the eye, suggesting its other potential applications. Age-related Macular Degeneration (AMD) is the leading cause of blindness in the developing world. There is no cure for this disease, and current treatments have several negative side effects associated with them, making finding other treatment options desirable.

OBJECTIVE

In this study, the potential applications in treating AMD for a more potent humanin derivative, AGA-HNG, were studied.

METHODS

AGA-HNG was synthesized and encapsulated in chitosan Nanoparticles (NPs), which were then characterized for their size, Encapsulation Efficiency (EE), and drug release. Their ability to suppress VEGF secretion and protect against oxidative apoptosis was studied in vitro using ARPE-19 cells. The chitosan NPs exhibited similar anti-VEGF properties and oxidative protection as the free protein while exhibiting superior pharmaceutical characteristics including biocompatibility and drug release.

RESULTS

Drug-loaded NPs exhibited a radius of 346nm with desirable pharmacokinetic properties including a stable surface charge (19.5 ± 3.7 mV) and steady drug release capacity. AGA-HNG showed great promise in mediating apoptosis in hypoxic cells. They were also able to significantly reduce VEGF expression in vitro with reduced cellular toxicity compared to the free drug.

CONCLUSION

The ability of this drug delivery system to reduce retinal apoptosis with desirable pharmacokinetic and biocompatible properties makes this a promising therapeutic option for AMD.

Dexamethasone intravitreal implant (OZURDEX®) for macular edema secondary to noninfectious uveitis: a review of the literature

Macular edema (ME) is the leading cause of visual loss in uveitis and may persist long after ocular inflammation has been resolved. Local steroids are the first line treatment for uveitis and uveitic ME. Dexamethasone intravitreal implant (OZURDEX®; Allergan, Inc., CA, USA) has been used to treat diabetic ME and ME secondary to retinal vein occlusion. Recent studies have also demonstrated that Ozurdex may be effective treatment for patients with persistent uveitic ME. In this review, we present the results of the real word studies concerning the efficacy and safety of Ozurdex for the treatment of uveitic ME.

Liposomes for effective drug delivery to the ocular posterior chamber

Background

Age-related macular degeneration (AMD) is a leading cause of severe visual deficits and blindness. Meanwhile, there is convincing evidence implicating oxidative stress, inflammation, and neovascularization in the onset and progression of AMD. Several studies have identified berberine hydrochloride and chrysophanol as potential treatments for ocular diseases based on their antioxidative, antiangiogenic, and anti-inflammatory effects. Unfortunately, their poor stability and bioavailability have limited their application. In order to overcome these disadvantages, we prepared a compound liposome system that can entrap these drugs simultaneously using the third polyamidoamine dendrimer (PAMAM G3.0) as a carrier.

Results

PAMAM G3.0-coated compound liposomes exhibited appreciable cellular permeability in human corneal epithelial cells and enhanced bio-adhesion on rabbit corneal epithelium. Moreover, coated liposomes greatly improved BBH bioavailability. Further, coated liposomes exhibited obviously protective effects in human retinal pigment epithelial cells and rat retinas after photooxidative retinal injury. Finally, administration of P-CBLs showed no sign of side effects on ocular surface structure in rabbits model.

Conclusions

The PAMAM G3.0-liposome system thus displayed a potential use for treating various ocular diseases.

Electronic supplementary material

The online version of this article (10.1186/s12951-019-0498-7) contains supplementary material, which is available to authorized users.

Diabetic retinopathy, a vascular and inflammatory disease: Therapeutic implications

Diabetic retinopathy (DR) is the most common microvascular complication of diabetes and the leading cause of visual impairment in the working-age population in the Western world. Diabetic macular oedema (DME) is one of the major complications of DR. Therapy with intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) drugs has become the gold standard treatment for DR and its complications. However, these drugs have no effect on the pathogenesis of DR and must be administered frequently via invasive intravitreal injections over many years. Thus, there is a pressing need to develop new therapeutic strategies to improve the treatment of this devastating disease. Indeed, an increasing volume of data supports the role of the inflammatory process in the pathogenesis of DR itself and its complications, including both increased retinal vascular permeability and neovascularization. Inflammation may also contribute to retinal neurodegeneration. Evidence that low-grade inflammation plays a critical role in the pathogenesis of DME has opened up new pathways and targets for the development of improved treatments. Anti-inflammatory compounds such as intravitreal glucocorticoids, topical non-steroidal anti-inflammatory drugs (NSAIDs), antioxidants, inflammatory molecule inhibitors, renin-angiotensin system (RAS) blockers and natural anti-inflammatory therapies may all be considered to reduce the rate of administration of antineovascularization agents in the treatment of DR. This report describes the current state of knowledge of the potential role of anti-inflammatory drugs in controlling the onset and evolution of DR and DME.

Nanodelivery of doxorubicin for age-related macular degeneration

OBJECTIVE

Polymeric nanoparticles (NPs) containing doxorubicin (DOX) were prepared for the inhibition of hypoxia-induced factor 1α (HIF-1α).

SIGNIFICANCE

HIF-1α is responsible for the upregulation of several angiogenic factors, including vascular endothelial growth factor (VEGF). DOX inhibits HIF-1α but is highly toxic. By encapsulating DOX in NPs, drug delivery will be sustained and toxicity will be reduced without limiting efficacy.

METHODS

DOX NPs were prepared using both polylactic coglycolic acid (PLGA) and chitosan. PLGA NPs were prepared via nanoprecipitation (NPC) and single and double emulsion diffusion (SE; DE). Chitosan NPs were formulated using ionic gelation (IG), and complex coacervation (CC). Size, polydispersity index (PDI), and zeta potential (ZP) were determined via dynamic light scattering (DLS) (n = 3). The encapsulation efficiency (EE), drug loading capacity (DLC) (n = 3) and in vitro drug release profiles (IVR) at 37 °C (n = 4) were analyzed via spectroscopy at 480 nm (λ_max). The cytotoxicity of each formulation as well as free DOX solution in ARPE-19 cells was determined via MTT assay after 24 h (n = 3). HIF-1α and VEGF inhibition in ARPE-19 cells were measured via ELISA (n = 3).

RESULTS

The results were consistent with the hypothesis; the NP formulations decreased HIF-1α and VEGF-A expression in ARPE-19 cells with reduced cytotoxicity. SE, DE, and CC demonstrated low ZP as well as the most rapid drug release of the tested formulations. FTIR confirmed the presence of DOX on the SE NP surface, indicating instability.

CONCLUSIONS

SE, DE, and CC destabilized. NPC was the most efficient formulation for the nanodelivery of DOX for AMD.

Treatment Duration and Side Effect Profile of Long-Term Use of Intravitreal Preservative-Free Triamcinolone Acetonide in Uveitis

PURPOSE

Noninfectious uveitis has been treated historically with corticosteroid therapy in varying doses and routes. Triesence, a preservative-free sterile formulation of triamcinolone acetonide, has been used in a wide spectrum of ocular pathologies, but there have been few large studies validating its dosing or detailing long-term side effects in uveitic disease. The primary aim of this study was to describe the relative duration of action and side effects of 2 doses of preservative-free intravitreal triamcinolone acetonide (PF-IVTA) in uveitis.

DESIGN

Retrospective, comparative consecutive case series.

METHODS

Charts of all patients receiving PF-IVTA (2 mg or 4 mg) in a defined time period (2012-2014) at the Cole Eye Institute were examined for patient demographics, time to treatment failure (TTF), use of systemic immunosuppression, use of intraocular pressure-lowering therapies, date of cataract surgery and glaucoma filtration surgery, and adverse events.

RESULTS

The final data set examined 514 injections in 214 eyes. Mean duration of follow-up was 1.5 years. There was similar demographic distribution between eyes that received 2 mg PF-IVTA only and eyes that received a combination of 4 + 2 mg PF-IVTA. No statistically significant difference in TTF between injection dosages was observed. There was a higher incidence of glaucoma filtering surgery and cataract surgery in eyes that received 4 + 2 mg PF-IVTA as well as a shorter time to glaucoma surgery, when compared to eyes that received 2 mg PF-IVTA alone.

CONCLUSIONS

This retrospective study supports that 2 mg PF-IVTA displayed noninferior treatment duration to 4 mg PF-IVTA, and may carry a significantly lower side-effect profile of cataract development and glaucoma filtering surgery.

Aflibercept Nanoformulation Inhibits VEGF Expression in Ocular In Vitro Model: A Preliminary Report

Age-related macular degeneration (AMD) is one of the leading causes of blindness in the United States, affecting approximately 11 million patients. AMD is caused primarily by an upregulation of vascular endothelial growth factor (VEGF). In recent years, aflibercept injections have been used to combat VEGF. However, this treatment requires frequent intravitreal injections, leading to low patient compliance and several adverse side effects including scarring, increased intraocular pressure, and retinal detachment. Polymeric nanoparticles have demonstrated the ability to deliver a sustained release of drug, thereby reducing the necessary injection frequency. Aflibercept (AFL) was encapsulated in poly lactic-co-glycolic acid (PLGA) nanoparticles (NPs) via double emulsion diffusion. Scanning electron microscopy showed the NPs were spherical and dynamic light scattering demonstrated that they were uniformly distributed (PDI < 1). The encapsulation efficiency and drug loading were 75.76% and 7.76% respectively. In vitro release studies showed a sustained release of drug; 75% of drug was released by the NPs in seven days compared to the full payload released in 24 h by the AFL solution. Future ocular in vivo studies are needed to confirm the biological effects of the NPs. Preliminary studies of the proposed aflibercept NPs demonstrated high encapsulation efficiency, a sustained drug release profile, and ideal physical characteristics for AMD treatment. This drug delivery system is an excellent candidate for further characterization using an ocular neovascularization in vivo model.

Role of Inflammation in Diabetic Retinopathy

Diabetic retinopathy is a common complication of diabetes and remains the leading cause of blindness among the working-age population. For decades, diabetic retinopathy was considered only a microvascular complication, but the retinal microvasculature is intimately associated with and governed by neurons and glia, which are affected even prior to clinically detectable vascular lesions. While progress has been made to improve the vascular alterations, there is still no treatment to counteract the early neuro-glial perturbations in diabetic retinopathy. Diabetes is a complex metabolic disorder, characterized by chronic hyperglycemia along with dyslipidemia, hypoinsulinemia and hypertension. Increasing evidence points to inflammation as one key player in diabetes-associated retinal perturbations, however, the exact underlying molecular mechanisms are not yet fully understood. Interlinked molecular pathways, such as oxidative stress, formation of advanced glycation end-products and increased expression of vascular endothelial growth factor have received a lot of attention as they all contribute to the inflammatory response. In the current review, we focus on the involvement of inflammation in the pathophysiology of diabetic retinopathy with special emphasis on the functional relationships between glial cells and neurons. Finally, we summarize recent advances using novel targets to inhibit inflammation in diabetic retinopathy.

Diabetic Microvascular Disease: An Endocrine Society Scientific Statement

Both type 1 and type 2 diabetes adversely affect the microvasculature in multiple organs. Our understanding of the genesis of this injury and of potential interventions to prevent, limit, or reverse injury/dysfunction is continuously evolving. This statement reviews biochemical/cellular pathways involved in facilitating and abrogating microvascular injury. The statement summarizes the types of injury/dysfunction that occur in the three classical diabetes microvascular target tissues, the eye, the kidney, and the peripheral nervous system; the statement also reviews information on the effects of diabetes and insulin resistance on the microvasculature of skin, brain, adipose tissue, and cardiac and skeletal muscle. Despite extensive and intensive research, it is disappointing that microvascular complications of diabetes continue to compromise the quantity and quality of life for patients with diabetes. Hopefully, by understanding and building on current research findings, we will discover new approaches for prevention and treatment that will be effective for future generations.

Clinical Applications of Dexamethasone for Aged Eyes

The risk of severe eye problems has been found to increase significantly with age, particularly between the fifth and sixth decades of life. Cataracts, dry eye, neovascular age-related macular degeneration, diabetic retinopathy and retinal vein occlusion (RVO) are very common and very different age-related ocular diseases that reduce the patient's quality of life. The rationale for using corticosteroids to treat anterior and posterior ocular segment diseases is driven by inflammation. Dexamethasone, one of the most powerful corticosteroids available, is widely used for topical or intravitreal administration. Topical dexamethasone has proven efficacy for the management of postoperative inflammation in the anterior segment after cataract surgery and symptom relief in dry-eye disease. A new sustained-release 700 µg dexamethasone intravitreal implant (DEX) was recently approved for the treatment of macular edema following RVO, diabetic macular edema, or non-infectious uveitis, and its use is increasing, especially when other therapeutic agents have failed. The most common side effects are increased intraocular pressure and cataract formation. The potency of DEX, alone or in combination with other agents, makes DEX a promising option for treating several retinal diseases.

New Drugs and New Posterior Delivery Methods in CME

PURPOSE

To discuss the characteristics, indications and adverse events (AEs) of sustained-release corticosteroid devices for the treatment of cystoid macular edema (CME).

RECENT FINDINGS

Ozurdex® is approved for the treatment of diabetic macular edema (DME), retinal vein occlusion related-CME and noninfectious posterior uveitis (NIPU). It releases dexamethasone over a maximum period of 6 months making repeated intravitreal injections necessary for recurrent CME. Iluvien® releases fluocinolone for up to 36 months and is effective for the treatment of chronic DME. Retisert® (Bausch & Lomb, Rochester, NY) also releases fluocinolone, and is approved for chronic NIPU. Both Iluvien® and Retisert® are non-biodegradable devices and are highly associated with cataract and glaucoma.

SUMMARY

Long-acting intraocular corticosteroid formulations offer a more predictable drug-release profile and reduced dosing frequency in comparison to conventional formulations of the same compounds but the risk-benefit ratio must be taken into consideration previous to the implantation of those devices.

Sustained release ophthalmic dexamethasone: In vitro in vivo correlations derived from the PK-Eye

Corticosteroids have long been used to treat intraocular inflammation by intravitreal injection. We describe dexamethasone loaded poly-DL-lactide-co-glycolide (PLGA) microparticles that were fabricated by thermally induced phase separation (TIPS). The dexamethasone loaded microparticles were evaluated using a two-compartment, in vitro aqueous outflow model of the eye (PK-Eye) that estimates drug clearance time from the back of the eye via aqueous outflow by the anterior route. A dexamethasone dose of 0.20±0.02mg in a 50μL volume of TIPS microparticles resulted in a clearance t_1/2 of 9.6±0.3days using simulated vitreous in the PK-Eye. Since corticosteroids can also clear through the retina, it is necessary to account for clearance through the back of the eye. Retinal permeability data, published human ocular pharmacokinetics (PK) and the PK-Eye clearance times were then used to establish in vitro in vivo correlations (IVIVCs) for intraocular clearance times of corticosteroid formulations. A t_1/2 of 48h was estimated for the dexamethasone-TIPS microparticles, which is almost 9 times longer than that reported for dexamethasone suspension in humans. The prediction of human clearance times of permeable molecules from the vitreous compartment can be determined by accounting for drug retinal permeation and determining the experimental clearance via the anterior aqueous outflow pathway using the PK-Eye.

Efficacy and safety of postvitrectomy intravitreal triamcinolone therapy for diabetic macular edema

PURPOSE

After vitrectomy, diffusion and clearance rates of numerous drugs are increased, leading to a shorter intravitreal half-life. This raises doubts about the efficacy of intravitreal therapies, as retina specialists generally believe that a shorter half-life compromises the drugs' therapeutic effect. We conducted a study to evaluate the functional and anatomical effect of intravitreal triamcinolone acetonide therapy (IVTA) in previously vitrectomized eyes with diabetic macular edema (DME).

METHODS

In this retrospective, multicenter case series study including vitrectomized patients with DME who underwent IVTA injections, central macular thickness (CMT) measured with spectral-domain optical coherence tomography and best-corrected visual acuity (BCVA) in Early Treatment Diabetic Retinopathy Study letters were evaluated after each procedure. All relevant medical data were collected, including previous ophthalmologic treatments and comorbidities.

RESULTS

Twenty vitrectomized eyes of 20 patients, mean age 58.1 years (range 40-72 years), were enrolled in the study. All patients presented DME and received at least one IVTA injection. Mean time between pars plana vitrectomy and IVTA was 12.9 ± 8.7 months. Mean pretreatment and posttreatment CMT was 438.8 ± 90.8 μm and 301.2 ± 76.2 μm, respectively, a difference that reached statistical significance (p&lt;0.001). Mean gain in BCVA letter score was 7.83 ± 14.9 letters after treatment (p = 0.039). Mean intraocular pressure was significantly increased after IVTA (17.2 ± 1.9 mm Hg at baseline vs 21.2 ± 4.59 mm Hg after IVTA, p = 0.002).

CONCLUSIONS

A positive anatomical and functional effect was observed in our cohort. Our results suggest that, despite prior vitrectomy, triamcinolone remains a valid therapeutic approach for eyes with persistent DME. Further prospective randomized studies with larger patient samples are needed to validate this conclusion.

Uveitic Macular Edema: Treatment Update

The aim of this review is to summarize recent developments in the treatment of uveitic macular edema (ME). ME represent a major cause of visual loss in uveitis and adequate management is crucial for the maintenance of useful vision in patients with chronic uveitis.

Supramolecular hydrogel of non-steroidal anti-inflammatory drugs: preparation, characterization and ocular biocompatibility

A supramolecular hydrogel based on a peptide (GFFY) and non-steroidal anti-inflammatory drugs (naproxen and ibuprofen) was synthesized for use as a topical gel.

Pharmacologic Treatment of Noninfectious Uveitis

Uveitis encompasses a spectrum of diseases whose common feature is intraocular inflammation, which may be infectious or noninfectious in etiology (Nussenblatt and Whitcup 2010). Infectious causes of uveitis are typically treated with appropriate antimicrobial therapy and will not be discussed in this chapter. Noninfectious uveitides are thought have an autoimmune component to their etiology and are thus treated with anti-inflammatory agents.

Efficacy of combined intravitreal bevacizumab and triamcinolone for branch retinal vein occlusion

Purpose:

To evaluate the efficacy of combined treatment with intravitreal bevacizumab (IVB) and triamcinolone acetate (IVT) for patients with macular edema secondary to branch retinal vein occlusion (BRVO).

Materials and Methods:

Retrospective analysis of 20 eyes injected with 1.25 mg IVB and 2 mg IVT for clinically identified BRVO within 8 weeks of onset. All patients lacked concomitant ocular pathology and completed 6 months’ follow-up. Clinical examination including LogMAR visual acuity (VA) and central macular thickness (CMT) by spectralis optical coherence tomography (OCT) was performed preoperatively and at 1, 3 and 6 months post-operatively.

Results:

Mean patient age was 61.3 years with a mean BRVO diagnosis time of 3 weeks at presentation. VA improved from logMAR 1.08 preoperatively to Mean logMAR VA of 0.55 ± 0.17 at 1 month (P < 0.001), 0.56 ± 0.21 at 3 months (P < 0.001), and 0.38 ± 0.1 at 6 months (P < 0.001) Mean CMT improved from 482 ± 107 μm preoperatively to 319 ± 53 μm at 1 month (P < 0.001), 344 ± 89 μm at 3 months (P < 0.001), and 241 ± 29 μm at 6 months (P < 0.001). Mean IOP preoperatively was 16.5 mmHg, 21 mmHg at 1 month, and 15 mmHg at 6 months. Six out of 20 patients (30%) were re-injected with IVB and IVT at 3 months.

Conclusions:

Early combined treatment with IVB and IVT is effective in improving anatomic and functional outcomes in patients with macular edema secondary to BRVO.

Analyses of Sequence Variants in the MYOC Gene and of Single Nucleotide Polymorphisms in the NR3C1 and FKBP5 Genes in Corticosteroid-Induced Ocular Hypertension

BACKGROUND

To perform an independent replication study to determine whether genetic variants in MYOC, NR3C1 and FKBP5 are involved in steroid-induced ocular hypertension.

MATERIALS AND METHODS

A retrospective case-control study was peformed on native Dutch patients who were treated with 4.0 mg intravitreal triamcinolone acetonide (IVTA). The patients were divided into an intraocular hypertension group (intraocular pressure >21 mmHg within a year after IVTA) and a non-intraocular hypertension group. The cohort was genotyped for 31 single-nucleotide polymorphisms (SNPs): 21 in NR3C1 and 10 in FKBP5. In addition, the open reading frame of MYOC was sequenced.

RESULTS

A total of 102 patients were included in this study: 58 steroid responders and 44 non-responders. No significant associations were found for the studied SNPs in NR3C1 and FKBP5. Heterozygous amino acid variants were detected in the MYOC gene in two patients of the non-intraocular hypertension group.

CONCLUSIONS

This study does not confirm a role for genetic variants in the MYOC, NR3C1 and FKBP5 genes in the pathogenesis of corticosteroid-induced ocular hypertension.

Noninfectious uveitis: strategies to optimize treatment compliance and adherence

Noninfectious uveitis includes a heterogenous group of sight-threatening ocular and systemic disorders. Significant progress has been made in the treatment of noninfectious uveitis in recent years, particularly with regard to the effective use of corticosteroids and non-corticosteroid immunosuppressive drugs, including biologic agents. All of these therapeutic approaches are limited, however, by any given patient’s ability to comply with and adhere to their prescribed treatment. In fact, compliance and adherence are among the most important patient-related determinants of treatment success. We discuss strategies to optimize compliance and adherence.

Comparison of intravitreal triamcinolone acetonide versus intravitreal bevacizumab as the primary treatment of clinically significant macular edema

OBJECTIVES

To evaluate the short-term efficacy of triamcinolone acetonide versus bevacizumab for the treatment of diabetic, clinically significant, macular edema with different optical coherence tomography findings.

METHODS

Fifty eyes of 45 consecutive patients with diabetic, clinically significant, macular edema were incorporated in this prospective interventional case series. Patients were divided into 3 groups according to findings on optical coherence tomography: 1) macular edema combined with serous retinal detachment (Group 1), 2) diffused macular thickening (Group 2), and 3) cystoid macular edema (Group 3). Patients from each group were treated with a single intravitreal injection of triamcinolone (IVTA) or 2 intravitreal injections of bevacizumab (IVB) with an interval of 6 weeks. Patients were observed at 6, 12, and 24 weeks after IVTA or the first IVB injection. Best-corrected visual acuity (BCVA) and central retinal thickness (CRT) were examined at each visit. Repeated-measures analysis of variance was used to compare the efficacy of the treatment groups.

RESULTS

In Group 1, IVTA showed more favorable effects on CRT reduction and BCVA improvement compared with IVB at 6, 12, and 24 weeks (P = 0.002, 0.001, 0.027 and P = 0.036, 0.001, 0.027), respectively. In Group 2, IVB had more CRT reduction than IVTA at 6 and 12 weeks (P = 0.013 and 0.036), although there was no significant difference in BCVA improvement between the 2 groups (P > 0.05). In Group 3, IVTA and IVB did not have significant effects on CRT reduction and BCVA improvement (P > 0.05).

CONCLUSION

The short-term efficacy of IVTA and IVB on treating clinically significant macular edema varied with different optical coherence tomography findings. In clinically significant macular edema combined with serous retinal detachment, IVTA may be more favorable than IVB in CRT reduction and BCVA improvement. In patients with diffused macular thickening, IVB may be better than IVTA in macular thickness reduction, although this does not translate to a significant improvement in BCVA.

Role of Concomitant Triamcinolone Acetonide Injection in Small-Gauge Vitrectomy for Idiopathic Epiretinal Membrane Peel

PURPOSE

The concomitant use of triamcinolone acetonide (TA) at the completion of pars plana vitrectomy for the treatment of epiretinal membrane may speed up the anatomical and functional outcomes of surgery. We report the outcome of patients undergoing small-gauge vitrectomy for idiopathic epiretinal membrane peel with or without adjuvant TA therapy.

DESIGN

This is a retrospective, single-center case series.

METHODS

We included 75 eyes of 75 individual patients. Twenty-six patients (group A) had an adjuvant TA injection during surgery, whereas 49 patients (group B) were not injected. We assessed the patients for change in visual acuity (VA) and central macular thickness before and after surgery.

RESULTS

Group A had a mean logarithm of the minimum angle of resolution VA of 0.63 ± 0.33 and 0.51 ± 0.31 preoperatively and 3 months after surgery, respectively. Group B had a mean logarithm of the minimum angle of resolution VA of 0.47 ± 0.17 and 0.36 ± 0.17 preoperatively and 3 months after surgery, respectively. No significant difference was found between the groups in change of VA. The mean central macular thickness for groups A and B patients before surgery was 474.12 ± 120 μm and 445 ± 85 μm, decreasing to 369 ± 70 μm and 386 ± 60 μm at the final visit, respectively. The difference in macular thickness reduction between the groups was statistically significant.

CONCLUSIONS

Anatomical and functional improvement was found in both groups after surgery. Macular thickness was further reduced in the group of patients treated with adjuvant TA.

A platform of integrative studies from in vitro to in vivo experiments: towards drug development for ischemic retinopathy

Pathologic angiogenesis induced by hypoxia is a hallmark of ischemic retinopathy including diabetic retinopathy and retinopathy of prematurity. These 2 diseases affect substantial number of working population and preterm babies, respectively, resulting in visual deterioration. It is essential for novel therapeutics for ischemic retinopathy to demonstrate the potency in reducing pathologic angiogenesis and the safety without definite toxicity on the retina and the whole body. In this review, we suggest a novel platform of integrative studies from in vitro to in vivo experiments on angiogenesis and toxicity with the aim of accelerating and facilitating the development of novel therapeutic agents for ischemic retinopathy. Robust in vitro and in vivo studies with bridging microfluidic and ex vivo systems help researchers to evaluate the efficacy and anticipate the toxicity of candidate drugs. We hope that novel therapeutic approach based on this platform will be developed in near future and reduce the incidence of vision loss from ischemic retinopathy.

Optimization of dexamethasone mixed nanomicellar formulation

The purpose of this study was to develop a clear aqueous mixed nanomicellar formulation (MNF) of dexamethasone utilizing both D-α-tocopherol polyethylene glycol-1000 succinate (Vit E TPGS) and octoxynol-40 (Oc-40). In this study, Vit E TPGS and Oc-40 are independent variables. Formulations were prepared following solvent evaporation method. A three level full-factorial design was applied to optimize the formulation based on entrapment efficiency, size, and polydispersity index (PDI). A specific blend of Vit E TPGS and Oc-40 at a particular wt% ratio (4.5:2.0) produced excellent drug entrapment, loading, small mixed nanomicellar size and narrow PDI. Solubility of DEX in MNF is improved by ~6.3-fold relative to normal aqueous solubility. Critical micellar concentration (CMC) for blend of polymers (4.5:2.0) was found to be lower (0.012 wt%) than the individual polymers (Vit E TPGS (0.025 wt%) and Oc-40 (0.107 wt%)). No significant effect on mixed nanomicellar size and PDI with one-factor or multi-factor interactions was observed. Qualitative (1)H NMR studies confirmed absence of free drug in the outer aqueous MNF medium. MNF appeared to be highly stable. Cytotoxicity studies on rabbit primary corneal epithelial cells did not indicate any toxicity suggesting MNF of dexamethasone is safe and suitable for human topical ocular drops after further in vivo evaluations.

Slow-release drug delivery through Elvax 40W to the rat retina: implications for the treatment of chronic conditions

Diseases of the retina are difficult to treat as the retina lies deep within the eye. Invasive methods of drug delivery are often needed to treat these diseases. Chronic retinal diseases such as retinal oedema or neovascularization usually require multiple intraocular injections to effectively treat the condition. However, the risks associated with these injections increase with repeated delivery of the drug. Therefore, alternative delivery methods need to be established in order to minimize the risks of reinjection. Several other investigations have developed methods to deliver drugs over extended time, through materials capable of releasing chemicals slowly into the eye. In this investigation, we outline the use of Elvax 40W, a copolymer resin, to act as a vehicle for drug delivery to the adult rat retina. The resin is made and loaded with the drug. The drug-resin complex is then implanted into the vitreous cavity, where it will slowly release the drug over time. This method was tested using 2-amino-4-phosphonobutyrate (APB), a glutamate analogue that blocks the light response of the retina. It was demonstrated that the APB was slowly released from the resin, and was able to block the retinal response by 7 days after implantation. This indicates that slow-release drug delivery using this copolymer resin is effective for treating the retina, and could be used therapeutically with further testing.