Description

High intraocular pressure is primarily linked to glaucoma, a chronic eye disease that ranks second in the world as the leading cause of irreversible vision loss. The inherent mechanics of ocular barriers, which prevent ophthalmic drugs from getting into the eye, make glaucoma treatment currently difficult. In order to address this issue, a wide range of carriers—inorganic, polymeric, hydrogel, or contact lens-based with specialized physical and chemical properties have been the subject of extensive research. The ocular barrier penetration, bioavailability, sustained drug release, tissue targeting, and IOP reduction that these carrier-drug formulations have demonstrated are just a few of the many areas in which they have made significant advancements. The delivery systems can be given in a variety of ways allowing the drugs to get to the damaged areas and assisting in the recovery of the damaged optical nerves. As a result, they are considered an effective treatment for glaucoma. The types of nano carriers, the method of delivery, the efficacy in vitro and in vivo, clinical availability, and the outlook for the future are all thoroughly examined in this review of recent advancements in glaucoma-specific ocular delivery formulations.

Nitric Oxide Donating Prostaglandins

There are currently a number of eye drops that can be used to lower elevated intraocular pressure, which is the most significant and only risk factor that can be treated and can cause glaucoma to progress to irreversible blindness if left untreated. Prostaglandins, beta-blockers, rho kinase inhibitors, nitric oxide donating prostaglandins, alpha-2 adrenergic agonists, carbonic anhydrase inhibitors, and muscarinic agonists are among the therapeutic molecules. The intraocular pressure can be effectively reduced by using any one of these therapeutic agents on its own or in combination. Some agents, like prostaglandins, need to be taken once a day, but others need to be taken multiple times a day. According to studies, less than half of patients who are prescribed glaucoma eye drops follow through, with approximately 60% of patients having difficulty administering them. Additionally, eye drops deliver medication to the eye in a high-frequency, pulsatile manner, with a peak drug concentration followed by a valley before the subsequent dose is given on the same day or the next. Drug effects can fluctuate as a result of the pulsating time course of drug concentrations or pharmacokinetics. Depending on the kind of drug being given, this could cause elevated intraocular pressure at different times throughout the day. Continuous drug delivery with associated sustained IOP suppression might be a better option. The reduced total dose and lower or slower systemic exposure, which reduces the risk of systemic side effects, is another potential advantage of controlled release delivery systems. This method of administering the drug also has negative effects, as is typically the case. For instance, any burst release from these systems could have a negative effect on the tissues, and continuous drug delivery may, in some instances, result in the development of drug tolerance. Each case should be evaluated individually for these concerns. A variety of delivery systems, including implants, microparticles, nanoparticles, gels, and combinations thereof, can be utilized to achieve sustained drug delivery. Typically, either pure drug or carrier materials are used to prepare these systems. The broad categories of reservoir and matrix drug delivery systems encompass composite drug delivery systems. The drug is contained within a core of a reservoir-type delivery system, surrounded by membranes that are either rate-limiting or impermeable and regulate the rate of drug release. In contrast, the drug is distributed throughout the matrix-type delivery system in the form of a carrier material. The drug can typically be delivered in a zero-order fashion constant rate of drug release for the majority of the delivery system's lifetime in reservoir-type systems, whereas matrix-type systems release the drug in a non-zero order fashion.

Injections of Radioactive Albumin

The lymphatic system, which primarily consists of lymphatic vessels and lymph nodes, is necessary for fluid homeostasis and immune function. In order to clear proteins, antigens, and debris from interstitial tissue and transport them to regional lymph nodes that are involved in immune surveillance and the inflammatory response, lymphatic vessels drain excess fluid. The lymphatic system's ability to remove fluid from the eye has been studied. Initially, molecular lymphatic markers were used to describe lymphatic channels in the ciliary bodies of sheep and humans. Using intracameral injections of radioactive albumin and fluorescent tracer, subsequent tracer studies on sheep and mice demonstrated their involvement in lymphatic drainage from the eye to the cervical lymph nodes. Using a combination of photoacoustic tomography and a near-infrared nanoparticle tracer, we have recently developed a non-invasive in vivo imaging strategy to quantify active lymphatic drainage from the eye. The spatial resolution of acoustic imaging and the high contrast of optical imaging are combined in this hybrid imaging strategy. Additionally, this quantitative non-invasive imaging platform has recently been applied to the investigation of age-related decreases in lymphatic clearance from the eye. The only risk factor that can be changed is elevated IOP, which is a major risk factor for developing glaucoma, the leading cause of irreversible blindness worldwide. Aqueous humor dynamics control IOP. There are a number of ways that the ciliary epithelium's secreted aqueous humor drains. Either through the trabecular meshwork, where it eventually reaches the episcleral veins and the blood circulation, or through the ciliary body into suprachoroidal spaces and the uveoscleral route, where it reaches the sclera. Aqueous inflow and/or outflow pathways are the targets of every glaucoma drug currently in use. The systemic lymphatics are manipulated by the sympathetic and parasympathetic systems of the autonomic nervous system. It is known that systemic lymphatic drainage depends on the sympathetic system's adrenergic system. Smooth muscle cells in mesenteric lymphatic collectors contain adrenergic nerve endings. In a mouse model of breast cancer, the lymphatic function is impaired when adrenergic receptors are blocked. The -adrenergic system may be involved in regulating eye lymphatic drainage, according to these systemic lymphatics findings. In fact, the presence of sympathetic nerve terminals in the ocular and periocular regions suggests that -adrenergic stimulation regulates ocular functions, such as blood flow and pressure inside the eye, naturally. Synthetic organic molecules called beta-blockers prevent endogenous catecholamine from binding to beta-adrenergic receptors and carrying out its intended function. It is unknown how adrenergic blockers like timolol affect the lymphatic drainage from the eye. A useful model for studying aqueous humor dynamics, its pharmacological determinants, lymphatic function, and the ocular immune system is the mouse, which exhibits dynamics that are comparable to those of humans.