Implantable drainage devices in glaucoma: Quo vadis?

Microfluidics in the eye: a review of glaucoma implants from an engineering perspective

Glaucoma is a progressive optic neuropathy in the eye, which is a leading cause of irreversible blindness worldwide and currently affects over 70 million individuals. Clinically, intraocular pressure (IOP) reduction is the only proven treatment to halt the progression of glaucoma. Microfluidic devices such as glaucoma drainage devices (GDDs) and minimally invasive glaucoma surgery (MIGS) devices are routinely used by ophthalmologists to manage elevated IOP, by creating an artificial pathway for the over-accumulated aqueous humor (AH) in a glaucomatous eye, when the natural pathways are severely blocked. Herein, a detailed modelling and analysis of both the natural microfluidic pathways of the AH in the eye and artificial microfluidic pathways formed additionally by the various glaucoma implants are conducted to provide an insight into the causes of the IOP abnormality and the improvement schemes of current implant designs. The mechanisms of representative glaucoma implants have been critically reviewed from the perspective of microfluidics, and we have categorized the current implants into four groups according to the targeted drainage sites of the AH, namely Schlemm's canal, suprachoroidal space, subconjunctival space, and ocular surface. In addition, we propose to divide the development and evolution of glaucoma implant designs into three technological waves, which include microtube (1st), microvalve (2nd) and microsystem (3rd). With the emerging trends of minimal invasiveness and artificial intelligence in the development of medical implants, we envision that a comprehensive glaucoma treatment microsystem is on the horizon, which is featured with active and wireless control of IOP, real-time continuous monitoring of IOP and aqueous rate, etc. The current review could potentially cast light on the unmatched needs, challenges, and future directions of the microfluidic structural and functional designs of glaucoma implants, which would enable an enhanced safety profile, reduced complications, increased efficacy of lowering IOP and reduced IOP fluctuations, closed-loop and on-demand control of IOP, etc.

Efficacy and Safety of Micropulse Transscleral Cyclophotocoagulation

Background: Early studies have shown that micropulse transscleral cyclophotocoagulation (MP-TSCPC) might be an effective and safe treatment option for lowering intraocular pressure (IOP). These studies were, however, somewhat limited, in particular by their retrospective nature and the length of follow-up. Therefore, we assessed the efficacy and safety of this novel treatment in a large cohort for up to 4 years. Methods: We performed a prospective cohort study, including all patients who were treated with MP-TSCPC since November 2017. The primary outcome was a reduction of IOP and the number of IOP-lowering medications. Results: The mean ± standard deviation baseline IOP and number of IOP-lowering medications were 26.6 ± 10.8 mmHg and 3.3 ± 1.3. IOP was reduced by 8.2 ± 7.9 (31.8% reduction), 6.9 ± 8.7 (28.1% reduction), and 7.1 ± 8.4 (30.2% reduction) mmHg after 6, 12, and 24 months, respectively (p < 0.001). The mean postoperative number of IOP-lowering medications was significantly reduced after 6 months by 0.6 ± 1.5 (p = 0.002) but was not significantly different after 12 or 24 months. Oral acetazolamide was significantly reduced from 28 (29%) eyes before treatment, to 9 (9%) at the last follow-up visit (p < 0.001). No major complications were observed after treatment. Conclusions: MP-TSCPC is a safe and effective treatment option for lowering IOP, but only reduced IOP-lowering medications in the first 6 months after treatment. However, MP-TSCPC is especially effective in getting patients off oral IOP-lowering drugs.

Efficacy of the XEN-Implant in Glaucoma and a Meta-Analysis of the Literature

Background: To assess the efficacy of XEN-implant surgery in patients with glaucoma, and to perform a meta-analysis of previously published results and compare these to our data. Methods: Prospective case-control study, in which all eyes that underwent XEN-implant surgery were included from 2015 onwards. Sub-analyses were performed for eyes that underwent XEN-implant as standalone procedure and as cataract-combined procedure. To compare our results, a systematic review was performed using the Embase, PubMed, Web of Science, and Cochrane database. Meta-analyses were performed by combining data (intraocular pressure (IOP), IOP-lowering medication, and complications) from the retrieved studies. Results: A total of 221 eyes underwent XEN-implant surgery (124 standalone and 97 cataract-combined). The mean ± standard deviation IOP declined from 18.8 ± 6.5 to 13.5 ± 4.3 mmHg at the last follow-up (p < 0.001; 28.9%). Postoperative, no significant differences in IOP or IOP-lowering medication were found between patients with and without combined procedure. Secondary surgeries were performed in 20.8% of eyes, most of them (63.0%) within six months. A meta-analysis of 19 studies retrieved from the systematic review showed a two-years postoperative pooled mean (weighted mean difference) of 14.5 (7.3) mmHg and 1.0 (1.6) for IOP and IOP-lowering medications, respectively (compared to 13.5 (5.3) mmHg and 3.2 (2.4) in the current study). Conclusion: XEN-implant surgery was effective and safe in lowering IOP and the number of IOP-lowering medications. There were no differences between standalone and combined procedures.

Smart nano-micro platforms for ophthalmological applications: The state-of-the-art and future perspectives

Smart nano-micro platforms have been extensively applied for diverse biomedical applications, mostly focusing on cancer therapy. In comparison with conventional nanotechnology, the smart nano-micro matrix can exhibit specific response to exogenous or endogenous triggers, and thus can achieve multiple functions e.g. site-specific drug delivery, bio-imaging and detection of bio-molecules. These intriguing techniques have expanded into ophthalmology in recent years, yet few works have been summarized in this field. In this work, we provide the state-of-the-art of diverse nano-micro platforms based on both the conventional materials (e.g. natural or synthetic polymers, lipid nanomaterials, metal and metal oxide nanoparticles) and emerging nanomaterials (e.g. up-conversion nanoparticles, quantum dots and carbon materials) in ophthalmology, with some smart nano/micro platformers highlighted. The common ocular diseases studied in the field of nano-micro systems are firstly introduced, and their therapeutic method and the related drawback in clinic treatment are presented. The recent progress of different materials for diverse ocular applications is then demonstrated, with the representative nano- and micro-systems highlighted in detail. At last, an in-depth discussion on the clinical translation challenges faced in this field and the future direction are provided. This review would allow the researchers to design more smart nanomedicines in a more rational manner for specific ophthalmology applications.

Novel Drug Delivery Systems Fighting Glaucoma: Formulation Obstacles and Solutions

Glaucoma is considered to be one of the biggest health problems in the world. It is the main cause of preventable blindness due to its asymptomatic nature in the early stages on the one hand and patients' non-adherence on the other. There are several approaches in glaucoma treatment, whereby this has to be individually designed for each patient. The first-line treatment is medication therapy. However, taking into account numerous disadvantages of conventional ophthalmic dosage forms, intensive work has been carried out on the development of novel drug delivery systems for glaucoma. This review aims to provide an overview of formulation solutions and strategies in the development of in situ gel systems, nanosystems, ocular inserts, contact lenses, collagen corneal shields, ocular implants, microneedles, and iontophoretic devices. The results of studies confirming the effectiveness of the aforementioned drug delivery systems were also briefly presented.

The Baerveldt Glaucoma Drainage Device: Efficacy, Safety, and Place in Therapy

Objective

This review summarizes published findings concerning the Baerveldt-350 glaucoma drainage device (GDD). Most studies focus on the comparison between different treatments; in this review, the primary focus is efficacy, safety, and place in therapy for the Baerveldt implant.

Methods

A systematic review was performed using the PubMed database for literature on March 13th, 2020. Efficacy was estimated by performing multiple meta-analyses to calculate the weighted mean difference in intraocular pressure (IOP) and IOP-lowering medication after surgery. In order to get an indication of the safety of the Baerveldt implant, all recorded peri- and postoperative complication were summarized.

Results

A total of 21 studies, including 12 randomized controlled trials, were included with a follow-up up to 5 years, covering a mix of glaucoma types. At the last follow-up point, at 5 years postoperative, the mean (95% confidence interval) reduction in IOP was 15.57 mmHg (14.43-16.71) and the mean (95% confidence interval) reduction in IOP-lowering medication after surgery was 1.81 (1.61-2.01). Most frequently observed postoperative complications were corneal edema (2-34%) and tube complications (4-33%). Rates of required re-intervention ranged from 0% to 51% across all included studies.

Conclusion

The efficacy of the Baerveldt implant is a significant reduction in IOP in the long term. The safety profile of the Baerveldt implant in terms of complication incidence is similar to those reported for other GDD's. For treatment of secondary glaucoma, we suggest the Baerveldt (or any other similar GDD) as the choice of treatment in patients where highest IOP reduction is desired.

Applications of microneedles in delivering drugs for various ocular diseases

Treatment of majority of eye diseases involve the use of eye drops or eye ointments, which have major drawbacks of needing frequent administration, lower bioavailability and inability to cross the various eye barriers. This necessitates the use of novel delivery systems. Microneedles (MNs) as an alternate novel delivery system facilitate drug delivery to various ocular diseases with promising approaches in healthcare. Advances in pharmaceutical technology have made MNs provide localized, effective, less invasive and targeted drug delivery in the eye. The purpose of this review is to provide an insight to efficacious therapeutic applications the MNs can bring in various ocular diseases. Out of which, glaucoma, age-related macular degeneration, uveitis, retinal vascular occlusion and retinitis pigmentosa are majorly discussed. Among the various types of MNs; solid coated, hollow and dissolving polymeric MNs are specifically focused for their applications in ocular diseases. In addition, MNs shows improvement in the visual acuity and decreases the progression of the different ocular diseases.