Table 4.

Advantages and disadvantages of the main methodologies used to prepare drug-loaded contact lenses (CLs).

Method	PROS	CONS
Soaking method	Easy, fast and low-cost method to load drugs into CLs	Massive use of solvents Low drug loadings, mainly due to a scarce penetration in the polymeric bulk High burst-effect in the release kinetics Rapid drug release
Solvent casting	Prolonged drug release Possible comfort and easy handling when thin and flexible films loaded with drugs are directly used as CLs	Possible degradation of active compounds due to the high process temperatures
Loading of vitamin E	Prolonged drug release Additional therapeutic properties, mainly antioxidant activity Blocking of UV radiation, which damage eye tissues	Possible worsening of the lens’ properties, as optical transparency, wettability, oxygen permeability A diffusion barrier mainly limited to hydrophilic compound
Incorporation of drug-loaded nanostructures or ring implants	Prolonged drug release	Possible worsening of the lens’ properties, as optical transparency, wettability, oxygen permeability Soaking method (with the related drawbacks) is often involved to incorporate drug-loaded particles
Molecular imprinting	Formation of cavities into the CLs support with proper size/shape and high-affinity for a specific drug High drug loadings Prolonged drug release	Possible undesired post-imprinting phenomena, like rearrangements of polymeric chains The selected drug as to be stable under the polymerization conditions
Supercritical technologies	High drug loadings Prolonged drug release Preservation of polymeric structure	Possible worsening of the lens’ optical properties, mainly due to a possible polymer foaming High operating costs due to high pressures