Table 2.

Comparative summary of drug delivery systems for ocular applications: key characteristics and benefits.

Drug Delivery System	Characteristics	Advantages
Nanomicelles	Spherical structures made up of surfactant molecules that self-assemble in water or polar solvents.	Ideal for encapsulating hydrophobic compounds. Enhanced ocular micro-adhesion. Increased efficiency with size reduction. Potential for stimulus–responsive release. Higher encapsulation capacity with increased amphiphilic polymers.
Liposomes	Vesicles composed of one or more phospholipid bilayers.	Flexible for chemical modification. Improved pre-corneal and conjunctival penetration. Enhanced bioactivity. Altered head group charge for selective interaction with mucin and corneal permeability. PAMAM-coated liposomes for better corneal barrier penetration.
Dispersed nanoparticles	Self-assembling supramolecular assemblies.	Increased carrying efficiency. Selective tissue accumulation. Controlled drug release. Various architectures are available. Enhanced permeability and retention effect. Mucoadhesive characteristics.
Dendrimers	Repeating multibranched polymers with high-density functional groups.	High encapsulation efficiency. Predictable biodistribution. Customizable hydrogels. Superior loading capacity. Narrow polydispersity. Can serve as building blocks for nanogels or liposomes.
Hydrogels	Highly absorbent polymer networks.	pH and thermoresponsive. Extended drug release. Injectable. Potential for targeted drug delivery. Ultrasound-responsive. Reduced frequency of intravitreal injections.
Nanosuspensions and nanoemulsions	Aqueous dispersions of insoluble drug particles or droplets of one liquid in another liquid.	Improved solubility and stability of poorly soluble drugs. Enhanced bioavailability. Prolonged drug release profiles. Stabilized with amphiphilic salts of cholesterol. Increased viscosity and retention time with dispersed oil phases and water-soluble polymers.
Microneedles	Small, needle-like structures.	Self-administration. Accurate drug delivery to the target site. Fewer complications compared to traditional injections. Hollow microneedles for greater guest molecule loading.