Potency of SARS-CoV-2 on Ocular Tissues

The current COVID-19 pandemic has affected more than 100 million people and resulted in morbidity and mortality around the world. Even though the disease caused by SARS-CoV-2 is characterized by respiratory tract involvement, previous and recent data also indicates ocular manifestation. Not surprisingly, cell entry point of the virus, ACE2 receptor, is widely expressed in ocular tissues ranging from conjunctiva to retina. Despite the sensibility of ocular tissues, the sophisticated defense mechanism of the eye might eliminate viral transmission. Nevertheless, the potential of systemic transmission through the nasolacrimal duct may not be eliminated. In the case of ocular involvement, the disease outcomes might be as treatable as conjunctivitis or as serious as retinal degeneration and the treatment regimen vary accordingly. Within these contingencies, our aim with this chapter is to shed light on molecular bases of SARS-CoV-2 infection, systemic invasiveness following ocular transmission, manifestation and permanent effects on ocular tissues

Niosomal Drug Delivery Systems for Ocular Disease—Recent Advances and Future Prospects

The eye is a complex organ consisting of several protective barriers and particular defense mechanisms. Since this organ is exposed to various infections, genetic disorders, and visual impairments it is essential to provide necessary drugs through the appropriate delivery routes and vehicles. The topical route of administration, as the most commonly used approach, maybe inefficient due to low drug bioavailability. New generation safe, effective, and targeted drug delivery systems based on nanocarriers have the capability to circumvent limitations associated with the complex anatomy of the eye. Nanotechnology, through various nanoparticles like niosomes, liposomes, micelles, dendrimers, and different polymeric vesicles play an active role in ophthalmology and ocular drug delivery systems. Niosomes, which are nano-vesicles composed of non-ionic surfactants, are emerging nanocarriers in drug delivery applications due to their solution/storage stability and cost-effectiveness. Additionally, they are biocompatible, biodegradable, flexible in structure, and suitable for loading both hydrophobic and hydrophilic drugs. These characteristics make niosomes promising nanocarriers in the treatment of ocular diseases. Hereby, we review niosome based drug delivery approaches in ophthalmology starting with different preparation methods of niosomes, drug loading/release mechanisms, characterization techniques of niosome nanocarriers and eventually successful applications in the treatment of ocular disorders